From 4f10e65a3f482d3d2e07eab75a8c8610f59b8112 Mon Sep 17 00:00:00 2001
From: Piotr Gorski <lucjan.lucjanov@gmail.com>
Date: Mon, 1 Nov 2021 12:32:31 +0100
Subject: [PATCH] UKSM for 5.15
Signed-off-by: Piotr Gorski <lucjan.lucjanov@gmail.com>
---
Documentation/vm/uksm.txt | 61 +
fs/exec.c | 1 +
fs/proc/meminfo.c | 4 +
include/linux/ksm.h | 43 +-
include/linux/mm_types.h | 3 +
include/linux/mmzone.h | 3 +
include/linux/pgtable.h | 17 +-
include/linux/sradix-tree.h | 77 +
include/linux/uksm.h | 149 +
kernel/fork.c | 2 +-
lib/Makefile | 2 +-
lib/sradix-tree.c | 476 +++
mm/Kconfig | 26 +
mm/Makefile | 3 +-
mm/ksm.c | 11 -
mm/memory.c | 33 +-
mm/mmap.c | 36 +
mm/uksm.c | 5614 +++++++++++++++++++++++++++++++++++
mm/vmstat.c | 3 +
19 files changed, 6538 insertions(+), 26 deletions(-)
create mode 100644 Documentation/vm/uksm.txt
create mode 100644 include/linux/sradix-tree.h
create mode 100644 include/linux/uksm.h
create mode 100644 lib/sradix-tree.c
create mode 100644 mm/uksm.c
diff --git a/Documentation/vm/uksm.txt b/Documentation/vm/uksm.txt
new file mode 100644
index 000000000..be19a3127
--- /dev/null
+++ b/Documentation/vm/uksm.txt
@@ -0,0 +1,61 @@
+The Ultra Kernel Samepage Merging feature
+----------------------------------------------
+/*
+ * Ultra KSM. Copyright (C) 2011-2012 Nai Xia
+ *
+ * This is an improvement upon KSM. Some basic data structures and routines
+ * are borrowed from ksm.c .
+ *
+ * Its new features:
+ * 1. Full system scan:
+ * It automatically scans all user processes' anonymous VMAs. Kernel-user
+ * interaction to submit a memory area to KSM is no longer needed.
+ *
+ * 2. Rich area detection:
+ * It automatically detects rich areas containing abundant duplicated
+ * pages based. Rich areas are given a full scan speed. Poor areas are
+ * sampled at a reasonable speed with very low CPU consumption.
+ *
+ * 3. Ultra Per-page scan speed improvement:
+ * A new hash algorithm is proposed. As a result, on a machine with
+ * Core(TM)2 Quad Q9300 CPU in 32-bit mode and 800MHZ DDR2 main memory, it
+ * can scan memory areas that does not contain duplicated pages at speed of
+ * 627MB/sec ~ 2445MB/sec and can merge duplicated areas at speed of
+ * 477MB/sec ~ 923MB/sec.
+ *
+ * 4. Thrashing area avoidance:
+ * Thrashing area(an VMA that has frequent Ksm page break-out) can be
+ * filtered out. My benchmark shows it's more efficient than KSM's per-page
+ * hash value based volatile page detection.
+ *
+ *
+ * 5. Misc changes upon KSM:
+ * * It has a fully x86-opitmized memcmp dedicated for 4-byte-aligned page
+ * comparison. It's much faster than default C version on x86.
+ * * rmap_item now has an struct *page member to loosely cache a
+ * address-->page mapping, which reduces too much time-costly
+ * follow_page().
+ * * The VMA creation/exit procedures are hooked to let the Ultra KSM know.
+ * * try_to_merge_two_pages() now can revert a pte if it fails. No break_
+ * ksm is needed for this case.
+ *
+ * 6. Full Zero Page consideration(contributed by Figo Zhang)
+ * Now uksmd consider full zero pages as special pages and merge them to an
+ * special unswappable uksm zero page.
+ */
+
+ChangeLog:
+
+2012-05-05 The creation of this Doc
+2012-05-08 UKSM 0.1.1.1 libc crash bug fix, api clean up, doc clean up.
+2012-05-28 UKSM 0.1.1.2 bug fix release
+2012-06-26 UKSM 0.1.2-beta1 first beta release for 0.1.2
+2012-07-2 UKSM 0.1.2-beta2
+2012-07-10 UKSM 0.1.2-beta3
+2012-07-26 UKSM 0.1.2 Fine grained speed control, more scan optimization.
+2012-10-13 UKSM 0.1.2.1 Bug fixes.
+2012-12-31 UKSM 0.1.2.2 Minor bug fixes.
+2014-07-02 UKSM 0.1.2.3 Fix a " __this_cpu_read() in preemptible bug".
+2015-04-22 UKSM 0.1.2.4 Fix a race condition that can sometimes trigger anonying warnings.
+2016-09-10 UKSM 0.1.2.5 Fix a bug in dedup ratio calculation.
+2017-02-26 UKSM 0.1.2.6 Fix a bug in hugetlbpage handling and a race bug with page migration.
diff --git a/fs/exec.c b/fs/exec.c
index a098c133d..da9985b3e 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -65,6 +65,7 @@
#include <linux/vmalloc.h>
#include <linux/io_uring.h>
#include <linux/syscall_user_dispatch.h>
+#include <linux/ksm.h>
#include <linux/uaccess.h>
#include <asm/mmu_context.h>
diff --git a/fs/proc/meminfo.c b/fs/proc/meminfo.c
index 6fa761c9c..45fd59a0d 100644
--- a/fs/proc/meminfo.c
+++ b/fs/proc/meminfo.c
@@ -108,6 +108,10 @@ static int meminfo_proc_show(struct seq_file *m, void *v)
#endif
show_val_kb(m, "PageTables: ",
global_node_page_state(NR_PAGETABLE));
+#ifdef CONFIG_UKSM
+ show_val_kb(m, "KsmZeroPages: ",
+ global_zone_page_state(NR_UKSM_ZERO_PAGES));
+#endif
show_val_kb(m, "NFS_Unstable: ", 0);
show_val_kb(m, "Bounce: ",
diff --git a/include/linux/ksm.h b/include/linux/ksm.h
index 161e8164a..f0dbdf3c9 100644
--- a/include/linux/ksm.h
+++ b/include/linux/ksm.h
@@ -21,20 +21,16 @@ struct mem_cgroup;
#ifdef CONFIG_KSM
int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
unsigned long end, int advice, unsigned long *vm_flags);
-int __ksm_enter(struct mm_struct *mm);
-void __ksm_exit(struct mm_struct *mm);
-static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
+static inline struct stable_node *page_stable_node(struct page *page)
{
- if (test_bit(MMF_VM_MERGEABLE, &oldmm->flags))
- return __ksm_enter(mm);
- return 0;
+ return PageKsm(page) ? page_rmapping(page) : NULL;
}
-static inline void ksm_exit(struct mm_struct *mm)
+static inline void set_page_stable_node(struct page *page,
+ struct stable_node *stable_node)
{
- if (test_bit(MMF_VM_MERGEABLE, &mm->flags))
- __ksm_exit(mm);
+ page->mapping = (void *)((unsigned long)stable_node | PAGE_MAPPING_KSM);
}
/*
@@ -54,6 +50,33 @@ struct page *ksm_might_need_to_copy(struct page *page,
void rmap_walk_ksm(struct page *page, struct rmap_walk_control *rwc);
void ksm_migrate_page(struct page *newpage, struct page *oldpage);
+#ifdef CONFIG_KSM_LEGACY
+int __ksm_enter(struct mm_struct *mm);
+void __ksm_exit(struct mm_struct *mm);
+static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
+{
+ if (test_bit(MMF_VM_MERGEABLE, &oldmm->flags))
+ return __ksm_enter(mm);
+ return 0;
+}
+
+static inline void ksm_exit(struct mm_struct *mm)
+{
+ if (test_bit(MMF_VM_MERGEABLE, &mm->flags))
+ __ksm_exit(mm);
+}
+
+#elif defined(CONFIG_UKSM)
+static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
+{
+ return 0;
+}
+
+static inline void ksm_exit(struct mm_struct *mm)
+{
+}
+#endif /* !CONFIG_UKSM */
+
#else /* !CONFIG_KSM */
static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
@@ -89,4 +112,6 @@ static inline void ksm_migrate_page(struct page *newpage, struct page *oldpage)
#endif /* CONFIG_MMU */
#endif /* !CONFIG_KSM */
+#include <linux/uksm.h>
+
#endif /* __LINUX_KSM_H */
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 7f8ee09c7..da86d7fc0 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -385,6 +385,9 @@ struct vm_area_struct {
struct mempolicy *vm_policy; /* NUMA policy for the VMA */
#endif
struct vm_userfaultfd_ctx vm_userfaultfd_ctx;
+#ifdef CONFIG_UKSM
+ struct vma_slot *uksm_vma_slot;
+#endif
} __randomize_layout;
struct core_thread {
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 6a1d79d84..4af26d848 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -158,6 +158,9 @@ enum zone_stat_item {
NR_ZSPAGES, /* allocated in zsmalloc */
#endif
NR_FREE_CMA_PAGES,
+#ifdef CONFIG_UKSM
+ NR_UKSM_ZERO_PAGES,
+#endif
NR_VM_ZONE_STAT_ITEMS };
enum node_stat_item {
diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
index e24d2c992..8e9d8af58 100644
--- a/include/linux/pgtable.h
+++ b/include/linux/pgtable.h
@@ -1137,13 +1137,26 @@ extern void untrack_pfn(struct vm_area_struct *vma, unsigned long pfn,
extern void untrack_pfn_moved(struct vm_area_struct *vma);
#endif
+#ifdef CONFIG_UKSM
+static inline int is_uksm_zero_pfn(unsigned long pfn)
+{
+ extern unsigned long uksm_zero_pfn;
+ return pfn == uksm_zero_pfn;
+}
+#else
+static inline int is_uksm_zero_pfn(unsigned long pfn)
+{
+ return 0;
+}
+#endif
+
#ifdef CONFIG_MMU
#ifdef __HAVE_COLOR_ZERO_PAGE
static inline int is_zero_pfn(unsigned long pfn)
{
extern unsigned long zero_pfn;
unsigned long offset_from_zero_pfn = pfn - zero_pfn;
- return offset_from_zero_pfn <= (zero_page_mask >> PAGE_SHIFT);
+ return offset_from_zero_pfn <= (zero_page_mask >> PAGE_SHIFT) || is_uksm_zero_pfn(pfn);
}
#define my_zero_pfn(addr) page_to_pfn(ZERO_PAGE(addr))
@@ -1152,7 +1165,7 @@ static inline int is_zero_pfn(unsigned long pfn)
static inline int is_zero_pfn(unsigned long pfn)
{
extern unsigned long zero_pfn;
- return pfn == zero_pfn;
+ return (pfn == zero_pfn) || (is_uksm_zero_pfn(pfn));
}
static inline unsigned long my_zero_pfn(unsigned long addr)
diff --git a/include/linux/sradix-tree.h b/include/linux/sradix-tree.h
new file mode 100644
index 000000000..d71edba6b
--- /dev/null
+++ b/include/linux/sradix-tree.h
@@ -0,0 +1,77 @@
+#ifndef _LINUX_SRADIX_TREE_H
+#define _LINUX_SRADIX_TREE_H
+
+
+#define INIT_SRADIX_TREE(root, mask) \
+do { \
+ (root)->height = 0; \
+ (root)->gfp_mask = (mask); \
+ (root)->rnode = NULL; \
+} while (0)
+
+#define ULONG_BITS (sizeof(unsigned long) * 8)
+#define SRADIX_TREE_INDEX_BITS (8 /* CHAR_BIT */ * sizeof(unsigned long))
+//#define SRADIX_TREE_MAP_SHIFT 6
+//#define SRADIX_TREE_MAP_SIZE (1UL << SRADIX_TREE_MAP_SHIFT)
+//#define SRADIX_TREE_MAP_MASK (SRADIX_TREE_MAP_SIZE-1)
+
+struct sradix_tree_node {
+ unsigned int height; /* Height from the bottom */
+ unsigned int count;
+ unsigned int fulls; /* Number of full sublevel trees */
+ struct sradix_tree_node *parent;
+ void *stores[0];
+};
+
+/* A simple radix tree implementation */
+struct sradix_tree_root {
+ unsigned int height;
+ struct sradix_tree_node *rnode;
+
+ /* Where found to have available empty stores in its sublevels */
+ struct sradix_tree_node *enter_node;
+ unsigned int shift;
+ unsigned int stores_size;
+ unsigned int mask;
+ unsigned long min; /* The first hole index */
+ unsigned long num;
+ //unsigned long *height_to_maxindex;
+
+ /* How the node is allocated and freed. */
+ struct sradix_tree_node *(*alloc)(void);
+ void (*free)(struct sradix_tree_node *node);
+
+ /* When a new node is added and removed */
+ void (*extend)(struct sradix_tree_node *parent, struct sradix_tree_node *child);
+ void (*assign)(struct sradix_tree_node *node, unsigned int index, void *item);
+ void (*rm)(struct sradix_tree_node *node, unsigned int offset);
+};
+
+struct sradix_tree_path {
+ struct sradix_tree_node *node;
+ int offset;
+};
+
+static inline
+void init_sradix_tree_root(struct sradix_tree_root *root, unsigned long shift)
+{
+ root->height = 0;
+ root->rnode = NULL;
+ root->shift = shift;
+ root->stores_size = 1UL << shift;
+ root->mask = root->stores_size - 1;
+}
+
+
+extern void *sradix_tree_next(struct sradix_tree_root *root,
+ struct sradix_tree_node *node, unsigned long index,
+ int (*iter)(void *, unsigned long));
+
+extern int sradix_tree_enter(struct sradix_tree_root *root, void **item, int num);
+
+extern void sradix_tree_delete_from_leaf(struct sradix_tree_root *root,
+ struct sradix_tree_node *node, unsigned long index);
+
+extern void *sradix_tree_lookup(struct sradix_tree_root *root, unsigned long index);
+
+#endif /* _LINUX_SRADIX_TREE_H */
diff --git a/include/linux/uksm.h b/include/linux/uksm.h
new file mode 100644
index 000000000..bb8651f53
--- /dev/null
+++ b/include/linux/uksm.h
@@ -0,0 +1,149 @@
+#ifndef __LINUX_UKSM_H
+#define __LINUX_UKSM_H
+/*
+ * Memory merging support.
+ *
+ * This code enables dynamic sharing of identical pages found in different
+ * memory areas, even if they are not shared by fork().
+ */
+
+/* if !CONFIG_UKSM this file should not be compiled at all. */
+#ifdef CONFIG_UKSM
+
+#include <linux/bitops.h>
+#include <linux/mm.h>
+#include <linux/pagemap.h>
+#include <linux/rmap.h>
+#include <linux/sched.h>
+
+extern unsigned long zero_pfn __read_mostly;
+extern unsigned long uksm_zero_pfn __read_mostly;
+extern struct page *empty_uksm_zero_page;
+
+/* must be done before linked to mm */
+extern void uksm_vma_add_new(struct vm_area_struct *vma);
+extern void uksm_remove_vma(struct vm_area_struct *vma);
+
+#define UKSM_SLOT_NEED_SORT (1 << 0)
+#define UKSM_SLOT_NEED_RERAND (1 << 1)
+#define UKSM_SLOT_SCANNED (1 << 2) /* It's scanned in this round */
+#define UKSM_SLOT_FUL_SCANNED (1 << 3)
+#define UKSM_SLOT_IN_UKSM (1 << 4)
+
+struct vma_slot {
+ struct sradix_tree_node *snode;
+ unsigned long sindex;
+
+ struct list_head slot_list;
+ unsigned long fully_scanned_round;
+ unsigned long dedup_num;
+ unsigned long pages_scanned;
+ unsigned long this_sampled;
+ unsigned long last_scanned;
+ unsigned long pages_to_scan;
+ struct scan_rung *rung;
+ struct page **rmap_list_pool;
+ unsigned int *pool_counts;
+ unsigned long pool_size;
+ struct vm_area_struct *vma;
+ struct mm_struct *mm;
+ unsigned long ctime_j;
+ unsigned long pages;
+ unsigned long flags;
+ unsigned long pages_cowed; /* pages cowed this round */
+ unsigned long pages_merged; /* pages merged this round */
+ unsigned long pages_bemerged;
+
+ /* when it has page merged in this eval round */
+ struct list_head dedup_list;
+};
+
+static inline void uksm_unmap_zero_page(pte_t pte)
+{
+ if (pte_pfn(pte) == uksm_zero_pfn)
+ __dec_zone_page_state(empty_uksm_zero_page, NR_UKSM_ZERO_PAGES);
+}
+
+static inline void uksm_map_zero_page(pte_t pte)
+{
+ if (pte_pfn(pte) == uksm_zero_pfn)
+ __inc_zone_page_state(empty_uksm_zero_page, NR_UKSM_ZERO_PAGES);
+}
+
+static inline void uksm_cow_page(struct vm_area_struct *vma, struct page *page)
+{
+ if (vma->uksm_vma_slot && PageKsm(page))
+ vma->uksm_vma_slot->pages_cowed++;
+}
+
+static inline void uksm_cow_pte(struct vm_area_struct *vma, pte_t pte)
+{
+ if (vma->uksm_vma_slot && pte_pfn(pte) == uksm_zero_pfn)
+ vma->uksm_vma_slot->pages_cowed++;
+}
+
+static inline int uksm_flags_can_scan(unsigned long vm_flags)
+{
+#ifdef VM_SAO
+ if (vm_flags & VM_SAO)
+ return 0;
+#endif
+
+ return !(vm_flags & (VM_PFNMAP | VM_IO | VM_DONTEXPAND |
+ VM_HUGETLB | VM_MIXEDMAP | VM_SHARED
+ | VM_MAYSHARE | VM_GROWSUP | VM_GROWSDOWN));
+}
+
+static inline void uksm_vm_flags_mod(unsigned long *vm_flags_p)
+{
+ if (uksm_flags_can_scan(*vm_flags_p))
+ *vm_flags_p |= VM_MERGEABLE;
+}
+
+/*
+ * Just a wrapper for BUG_ON for where ksm_zeropage must not be. TODO: it will
+ * be removed when uksm zero page patch is stable enough.
+ */
+static inline void uksm_bugon_zeropage(pte_t pte)
+{
+ BUG_ON(pte_pfn(pte) == uksm_zero_pfn);
+}
+#else
+static inline void uksm_vma_add_new(struct vm_area_struct *vma)
+{
+}
+
+static inline void uksm_remove_vma(struct vm_area_struct *vma)
+{
+}
+
+static inline void uksm_unmap_zero_page(pte_t pte)
+{
+}
+
+static inline void uksm_map_zero_page(pte_t pte)
+{
+}
+
+static inline void uksm_cow_page(struct vm_area_struct *vma, struct page *page)
+{
+}
+
+static inline void uksm_cow_pte(struct vm_area_struct *vma, pte_t pte)
+{
+}
+
+static inline int uksm_flags_can_scan(unsigned long vm_flags)
+{
+ return 0;
+}
+
+static inline void uksm_vm_flags_mod(unsigned long *vm_flags_p)
+{
+}
+
+static inline void uksm_bugon_zeropage(pte_t pte)
+{
+}
+#endif /* !CONFIG_UKSM */
+#endif /* __LINUX_UKSM_H */
diff --git a/kernel/fork.c b/kernel/fork.c
index 38681ad44..af32e377d 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -604,7 +604,7 @@ static __latent_entropy int dup_mmap(struct mm_struct *mm,
__vma_link_rb(mm, tmp, rb_link, rb_parent);
rb_link = &tmp->vm_rb.rb_right;
rb_parent = &tmp->vm_rb;
-
+ uksm_vma_add_new(tmp);
mm->map_count++;
if (!(tmp->vm_flags & VM_WIPEONFORK))
retval = copy_page_range(tmp, mpnt);
diff --git a/lib/Makefile b/lib/Makefile
index a841be524..446bb9818 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -28,7 +28,7 @@ CFLAGS_string.o += -fno-stack-protector
endif
lib-y := ctype.o string.o vsprintf.o cmdline.o \
- rbtree.o radix-tree.o timerqueue.o xarray.o \
+ rbtree.o radix-tree.o sradix-tree.o timerqueue.o xarray.o \
idr.o extable.o sha1.o irq_regs.o argv_split.o \
flex_proportions.o ratelimit.o show_mem.o \
is_single_threaded.o plist.o decompress.o kobject_uevent.o \
diff --git a/lib/sradix-tree.c b/lib/sradix-tree.c
new file mode 100644
index 000000000..ab21e6309
--- /dev/null
+++ b/lib/sradix-tree.c
@@ -0,0 +1,476 @@
+#include <linux/errno.h>
+#include <linux/mm.h>
+#include <linux/mman.h>
+#include <linux/spinlock.h>
+#include <linux/slab.h>
+#include <linux/gcd.h>
+#include <linux/sradix-tree.h>
+
+static inline int sradix_node_full(struct sradix_tree_root *root, struct sradix_tree_node *node)
+{
+ return node->fulls == root->stores_size ||
+ (node->height == 1 && node->count == root->stores_size);
+}
+
+/*
+ * Extend a sradix tree so it can store key @index.
+ */
+static int sradix_tree_extend(struct sradix_tree_root *root, unsigned long index)
+{
+ struct sradix_tree_node *node;
+ unsigned int height;
+
+ if (unlikely(root->rnode == NULL)) {
+ if (!(node = root->alloc()))
+ return -ENOMEM;
+
+ node->height = 1;
+ root->rnode = node;
+ root->height = 1;
+ }
+
+ /* Figure out what the height should be. */
+ height = root->height;
+ index >>= root->shift * height;
+
+ while (index) {
+ index >>= root->shift;
+ height++;
+ }
+
+ while (height > root->height) {
+ unsigned int newheight;
+
+ if (!(node = root->alloc()))
+ return -ENOMEM;
+
+ /* Increase the height. */
+ node->stores[0] = root->rnode;
+ root->rnode->parent = node;
+ if (root->extend)
+ root->extend(node, root->rnode);
+
+ newheight = root->height + 1;
+ node->height = newheight;
+ node->count = 1;
+ if (sradix_node_full(root, root->rnode))
+ node->fulls = 1;
+
+ root->rnode = node;
+ root->height = newheight;
+ }
+
+ return 0;
+}
+
+/*
+ * Search the next item from the current node, that is not NULL
+ * and can satify root->iter().
+ */
+void *sradix_tree_next(struct sradix_tree_root *root,
+ struct sradix_tree_node *node, unsigned long index,
+ int (*iter)(void *item, unsigned long height))
+{
+ unsigned long offset;
+ void *item;
+
+ if (unlikely(node == NULL)) {
+ node = root->rnode;
+ for (offset = 0; offset < root->stores_size; offset++) {
+ item = node->stores[offset];
+ if (item && (!iter || iter(item, node->height)))
+ break;
+ }
+
+ if (unlikely(offset >= root->stores_size))
+ return NULL;
+
+ if (node->height == 1)
+ return item;
+ else
+ goto go_down;
+ }
+
+ while (node) {
+ offset = (index & root->mask) + 1;
+ for (; offset < root->stores_size; offset++) {
+ item = node->stores[offset];
+ if (item && (!iter || iter(item, node->height)))
+ break;
+ }
+
+ if (offset < root->stores_size)
+ break;
+
+ node = node->parent;
+ index >>= root->shift;
+ }
+
+ if (!node)
+ return NULL;
+
+ while (node->height > 1) {
+go_down:
+ node = item;
+ for (offset = 0; offset < root->stores_size; offset++) {
+ item = node->stores[offset];
+ if (item && (!iter || iter(item, node->height)))
+ break;
+ }
+
+ if (unlikely(offset >= root->stores_size))
+ return NULL;
+ }
+
+ BUG_ON(offset > root->stores_size);
+
+ return item;
+}
+
+/*
+ * Blindly insert the item to the tree. Typically, we reuse the
+ * first empty store item.
+ */
+int sradix_tree_enter(struct sradix_tree_root *root, void **item, int num)
+{
+ unsigned long index;
+ unsigned int height;
+ struct sradix_tree_node *node, *tmp = NULL;
+ int offset, offset_saved;
+ void **store = NULL;
+ int error, i, j, shift;
+
+go_on:
+ index = root->min;
+
+ if (root->enter_node && !sradix_node_full(root, root->enter_node)) {
+ node = root->enter_node;
+ BUG_ON((index >> (root->shift * root->height)));
+ } else {
+ node = root->rnode;
+ if (node == NULL || (index >> (root->shift * root->height))
+ || sradix_node_full(root, node)) {
+ error = sradix_tree_extend(root, index);
+ if (error)
+ return error;
+
+ node = root->rnode;
+ }
+ }
+
+
+ height = node->height;
+ shift = (height - 1) * root->shift;
+ offset = (index >> shift) & root->mask;
+ while (shift > 0) {
+ offset_saved = offset;
+ for (; offset < root->stores_size; offset++) {
+ store = &node->stores[offset];
+ tmp = *store;
+
+ if (!tmp || !sradix_node_full(root, tmp))
+ break;
+ }
+ BUG_ON(offset >= root->stores_size);
+
+ if (offset != offset_saved) {
+ index += (offset - offset_saved) << shift;
+ index &= ~((1UL << shift) - 1);
+ }
+
+ if (!tmp) {
+ if (!(tmp = root->alloc()))
+ return -ENOMEM;
+
+ tmp->height = shift / root->shift;
+ *store = tmp;
+ tmp->parent = node;
+ node->count++;
+// if (root->extend)
+// root->extend(node, tmp);
+ }
+
+ node = tmp;
+ shift -= root->shift;
+ offset = (index >> shift) & root->mask;
+ }
+
+ BUG_ON(node->height != 1);
+
+
+ store = &node->stores[offset];
+ for (i = 0, j = 0;
+ j < root->stores_size - node->count &&
+ i < root->stores_size - offset && j < num; i++) {
+ if (!store[i]) {
+ store[i] = item[j];
+ if (root->assign)
+ root->assign(node, index + i, item[j]);
+ j++;
+ }
+ }
+
+ node->count += j;
+ root->num += j;
+ num -= j;
+
+ while (sradix_node_full(root, node)) {
+ node = node->parent;
+ if (!node)
+ break;
+
+ node->fulls++;
+ }
+
+ if (unlikely(!node)) {
+ /* All nodes are full */
+ root->min = 1 << (root->height * root->shift);
+ root->enter_node = NULL;
+ } else {
+ root->min = index + i - 1;
+ root->min |= (1UL << (node->height - 1)) - 1;
+ root->min++;
+ root->enter_node = node;
+ }
+
+ if (num) {
+ item += j;
+ goto go_on;
+ }
+
+ return 0;
+}
+
+
+/**
+ * sradix_tree_shrink - shrink height of a sradix tree to minimal
+ * @root sradix tree root
+ *
+ */
+static inline void sradix_tree_shrink(struct sradix_tree_root *root)
+{
+ /* try to shrink tree height */
+ while (root->height > 1) {
+ struct sradix_tree_node *to_free = root->rnode;
+
+ /*
+ * The candidate node has more than one child, or its child
+ * is not at the leftmost store, we cannot shrink.
+ */
+ if (to_free->count != 1 || !to_free->stores[0])
+ break;
+
+ root->rnode = to_free->stores[0];
+ root->rnode->parent = NULL;
+ root->height--;
+ if (unlikely(root->enter_node == to_free))
+ root->enter_node = NULL;
+ root->free(to_free);
+ }
+}
+
+/*
+ * Del the item on the known leaf node and index
+ */
+void sradix_tree_delete_from_leaf(struct sradix_tree_root *root,
+ struct sradix_tree_node *node, unsigned long index)
+{
+ unsigned int offset;
+ struct sradix_tree_node *start, *end;
+
+ BUG_ON(node->height != 1);
+
+ start = node;
+ while (node && !(--node->count))
+ node = node->parent;
+
+ end = node;
+ if (!node) {
+ root->rnode = NULL;
+ root->height = 0;
+ root->min = 0;
+ root->num = 0;
+ root->enter_node = NULL;
+ } else {
+ offset = (index >> (root->shift * (node->height - 1))) & root->mask;
+ if (root->rm)
+ root->rm(node, offset);
+ node->stores[offset] = NULL;
+ root->num--;
+ if (root->min > index) {
+ root->min = index;
+ root->enter_node = node;
+ }
+ }
+
+ if (start != end) {
+ do {
+ node = start;
+ start = start->parent;
+ if (unlikely(root->enter_node == node))
+ root->enter_node = end;
+ root->free(node);
+ } while (start != end);
+
+ /*
+ * Note that shrink may free "end", so enter_node still need to
+ * be checked inside.
+ */
+ sradix_tree_shrink(root);
+ } else if (node->count == root->stores_size - 1) {
+ /* It WAS a full leaf node. Update the ancestors */
+ node = node->parent;
+ while (node) {
+ node->fulls--;
+ if (node->fulls != root->stores_size - 1)
+ break;
+
+ node = node->parent;
+ }
+ }
+}
+
+void *sradix_tree_lookup(struct sradix_tree_root *root, unsigned long index)
+{
+ unsigned int height, offset;
+ struct sradix_tree_node *node;
+ int shift;
+
+ node = root->rnode;
+ if (node == NULL || (index >> (root->shift * root->height)))
+ return NULL;
+
+ height = root->height;
+ shift = (height - 1) * root->shift;
+
+ do {
+ offset = (index >> shift) & root->mask;
+ node = node->stores[offset];
+ if (!node)
+ return NULL;
+
+ shift -= root->shift;
+ } while (shift >= 0);
+
+ return node;
+}
+
+/*
+ * Return the item if it exists, otherwise create it in place
+ * and return the created item.
+ */
+void *sradix_tree_lookup_create(struct sradix_tree_root *root,
+ unsigned long index, void *(*item_alloc)(void))
+{
+ unsigned int height, offset;
+ struct sradix_tree_node *node, *tmp;
+ void *item;
+ int shift, error;
+
+ if (root->rnode == NULL || (index >> (root->shift * root->height))) {
+ if (item_alloc) {
+ error = sradix_tree_extend(root, index);
+ if (error)
+ return NULL;
+ } else {
+ return NULL;
+ }
+ }
+
+ node = root->rnode;
+ height = root->height;
+ shift = (height - 1) * root->shift;
+
+ do {
+ offset = (index >> shift) & root->mask;
+ if (!node->stores[offset]) {
+ if (!(tmp = root->alloc()))
+ return NULL;
+
+ tmp->height = shift / root->shift;
+ node->stores[offset] = tmp;
+ tmp->parent = node;
+ node->count++;
+ node = tmp;
+ } else {
+ node = node->stores[offset];
+ }
+
+ shift -= root->shift;
+ } while (shift > 0);
+
+ BUG_ON(node->height != 1);
+ offset = index & root->mask;
+ if (node->stores[offset]) {
+ return node->stores[offset];
+ } else if (item_alloc) {
+ if (!(item = item_alloc()))
+ return NULL;
+
+ node->stores[offset] = item;
+
+ /*
+ * NOTE: we do NOT call root->assign here, since this item is
+ * newly created by us having no meaning. Caller can call this
+ * if it's necessary to do so.
+ */
+
+ node->count++;
+ root->num++;
+
+ while (sradix_node_full(root, node)) {
+ node = node->parent;
+ if (!node)
+ break;
+
+ node->fulls++;
+ }
+
+ if (unlikely(!node)) {
+ /* All nodes are full */
+ root->min = 1 << (root->height * root->shift);
+ } else {
+ if (root->min == index) {
+ root->min |= (1UL << (node->height - 1)) - 1;
+ root->min++;
+ root->enter_node = node;
+ }
+ }
+
+ return item;
+ } else {
+ return NULL;
+ }
+
+}
+
+int sradix_tree_delete(struct sradix_tree_root *root, unsigned long index)
+{
+ unsigned int height, offset;
+ struct sradix_tree_node *node;
+ int shift;
+
+ node = root->rnode;
+ if (node == NULL || (index >> (root->shift * root->height)))
+ return -ENOENT;
+
+ height = root->height;
+ shift = (height - 1) * root->shift;
+
+ do {
+ offset = (index >> shift) & root->mask;
+ node = node->stores[offset];
+ if (!node)
+ return -ENOENT;
+
+ shift -= root->shift;
+ } while (shift > 0);
+
+ offset = index & root->mask;
+ if (!node->stores[offset])
+ return -ENOENT;
+
+ sradix_tree_delete_from_leaf(root, node, index);
+
+ return 0;
+}
diff --git a/mm/Kconfig b/mm/Kconfig
index d16ba9249..744b0ed24 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -301,6 +301,32 @@ config KSM
See Documentation/vm/ksm.rst for more information: KSM is inactive
until a program has madvised that an area is MADV_MERGEABLE, and
root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set).
+choice
+ prompt "Choose UKSM/KSM strategy"
+ default UKSM
+ depends on KSM
+ help
+ This option allows to select a UKSM/KSM stragety.
+
+config UKSM
+ bool "Ultra-KSM for page merging"
+ depends on KSM
+ help
+ UKSM is inspired by the Linux kernel project \u2014 KSM(Kernel Same
+ page Merging), but with a fundamentally rewritten core algorithm. With
+ an advanced algorithm, UKSM now can transparently scans all anonymously
+ mapped user space applications with an significantly improved scan speed
+ and CPU efficiency. Since KVM is friendly to KSM, KVM can also benefit from
+ UKSM. Now UKSM has its first stable release and first real world enterprise user.
+ For more information, please goto its project page.
+ (github.com/dolohow/uksm)
+
+config KSM_LEGACY
+ bool "Legacy KSM implementation"
+ depends on KSM
+ help
+ The legacy KSM implementation from Red Hat.
+endchoice
config DEFAULT_MMAP_MIN_ADDR
int "Low address space to protect from user allocation"
diff --git a/mm/Makefile b/mm/Makefile
index fc60a40ce..69015e892 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -81,7 +81,8 @@ obj-$(CONFIG_SPARSEMEM) += sparse.o
obj-$(CONFIG_SPARSEMEM_VMEMMAP) += sparse-vmemmap.o
obj-$(CONFIG_SLOB) += slob.o
obj-$(CONFIG_MMU_NOTIFIER) += mmu_notifier.o
-obj-$(CONFIG_KSM) += ksm.o
+obj-$(CONFIG_KSM_LEGACY) += ksm.o
+obj-$(CONFIG_UKSM) += uksm.o
obj-$(CONFIG_PAGE_POISONING) += page_poison.o
obj-$(CONFIG_SLAB) += slab.o
obj-$(CONFIG_SLUB) += slub.o
diff --git a/mm/ksm.c b/mm/ksm.c
index a5716fdec..b8a7f01cd 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -852,17 +852,6 @@ static int unmerge_ksm_pages(struct vm_area_struct *vma,
return err;
}
-static inline struct stable_node *page_stable_node(struct page *page)
-{
- return PageKsm(page) ? page_rmapping(page) : NULL;
-}
-
-static inline void set_page_stable_node(struct page *page,
- struct stable_node *stable_node)
-{
- page->mapping = (void *)((unsigned long)stable_node | PAGE_MAPPING_KSM);
-}
-
#ifdef CONFIG_SYSFS
/*
* Only called through the sysfs control interface:
diff --git a/mm/memory.c b/mm/memory.c
index c52be6d6b..c5512e697 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -157,6 +157,25 @@ EXPORT_SYMBOL(zero_pfn);
unsigned long highest_memmap_pfn __read_mostly;
+#ifdef CONFIG_UKSM
+unsigned long uksm_zero_pfn __read_mostly;
+EXPORT_SYMBOL_GPL(uksm_zero_pfn);
+struct page *empty_uksm_zero_page;
+
+static int __init setup_uksm_zero_page(void)
+{
+ empty_uksm_zero_page = alloc_pages(__GFP_ZERO & ~__GFP_MOVABLE, 0);
+ if (!empty_uksm_zero_page)
+ panic("Oh boy, that early out of memory?");
+
+ SetPageReserved(empty_uksm_zero_page);
+ uksm_zero_pfn = page_to_pfn(empty_uksm_zero_page);
+
+ return 0;
+}
+core_initcall(setup_uksm_zero_page);
+#endif
+
/*
* CONFIG_MMU architectures set up ZERO_PAGE in their paging_init()
*/
@@ -172,6 +191,7 @@ void mm_trace_rss_stat(struct mm_struct *mm, int member, long count)
trace_rss_stat(mm, member, count);
}
+
#if defined(SPLIT_RSS_COUNTING)
void sync_mm_rss(struct mm_struct *mm)
@@ -954,6 +974,11 @@ copy_present_pte(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma,
get_page(page);
page_dup_rmap(page, false);
rss[mm_counter(page)]++;
+
+ /* Should return NULL in vm_normal_page() */
+ uksm_bugon_zeropage(pte);
+ } else {
+ uksm_map_zero_page(pte);
}
/*
@@ -1346,8 +1371,10 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb,
ptent = ptep_get_and_clear_full(mm, addr, pte,
tlb->fullmm);
tlb_remove_tlb_entry(tlb, pte, addr);
- if (unlikely(!page))
+ if (unlikely(!page)) {
+ uksm_unmap_zero_page(ptent);
continue;
+ }
if (!PageAnon(page)) {
if (pte_dirty(ptent)) {
@@ -2753,6 +2780,7 @@ static inline bool cow_user_page(struct page *dst, struct page *src,
if (likely(src)) {
copy_user_highpage(dst, src, addr, vma);
+ uksm_cow_page(vma, src);
return true;
}
@@ -2999,6 +3027,7 @@ static vm_fault_t wp_page_copy(struct vm_fault *vmf)
vmf->address);
if (!new_page)
goto oom;
+ uksm_cow_pte(vma, vmf->orig_pte);
} else {
new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma,
vmf->address);
@@ -3041,7 +3070,9 @@ static vm_fault_t wp_page_copy(struct vm_fault *vmf)
mm_counter_file(old_page));
inc_mm_counter_fast(mm, MM_ANONPAGES);
}
+ uksm_bugon_zeropage(vmf->orig_pte);
} else {
+ uksm_unmap_zero_page(vmf->orig_pte);
inc_mm_counter_fast(mm, MM_ANONPAGES);
}
flush_cache_page(vma, vmf->address, pte_pfn(vmf->orig_pte));
diff --git a/mm/mmap.c b/mm/mmap.c
index 88dcc5c25..b93c12938 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -46,6 +46,7 @@
#include <linux/moduleparam.h>
#include <linux/pkeys.h>
#include <linux/oom.h>
+#include <linux/ksm.h>
#include <linux/sched/mm.h>
#include <linux/uaccess.h>
@@ -185,6 +186,7 @@ static struct vm_area_struct *remove_vma(struct vm_area_struct *vma)
if (vma->vm_file)
fput(vma->vm_file);
mpol_put(vma_policy(vma));
+ uksm_remove_vma(vma);
vm_area_free(vma);
return next;
}
@@ -751,9 +753,16 @@ int __vma_adjust(struct vm_area_struct *vma, unsigned long start,
long adjust_next = 0;
int remove_next = 0;
+/*
+ * to avoid deadlock, ksm_remove_vma must be done before any spin_lock is
+ * acquired
+ */
+ uksm_remove_vma(vma);
+
if (next && !insert) {
struct vm_area_struct *exporter = NULL, *importer = NULL;
+ uksm_remove_vma(next);
if (end >= next->vm_end) {
/*
* vma expands, overlapping all the next, and
@@ -884,6 +893,7 @@ int __vma_adjust(struct vm_area_struct *vma, unsigned long start,
end_changed = true;
}
vma->vm_pgoff = pgoff;
+
if (adjust_next) {
next->vm_start += adjust_next;
next->vm_pgoff += adjust_next >> PAGE_SHIFT;
@@ -988,6 +998,7 @@ int __vma_adjust(struct vm_area_struct *vma, unsigned long start,
if (remove_next == 2) {
remove_next = 1;
end = next->vm_end;
+ uksm_remove_vma(next);
goto again;
}
else if (next)
@@ -1014,10 +1025,14 @@ int __vma_adjust(struct vm_area_struct *vma, unsigned long start,
*/
VM_WARN_ON(mm->highest_vm_end != vm_end_gap(vma));
}
+ } else {
+ if (next && !insert)
+ uksm_vma_add_new(next);
}
if (insert && file)
uprobe_mmap(insert);
+ uksm_vma_add_new(vma);
validate_mm(mm);
return 0;
@@ -1470,6 +1485,9 @@ unsigned long do_mmap(struct file *file, unsigned long addr,
vm_flags = calc_vm_prot_bits(prot, pkey) | calc_vm_flag_bits(flags) |
mm->def_flags | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC;
+ /* If uksm is enabled, we add VM_MERGEABLE to new VMAs. */
+ uksm_vm_flags_mod(&vm_flags);
+
if (flags & MAP_LOCKED)
if (!can_do_mlock())
return -EPERM;
@@ -1843,6 +1861,7 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
if (file && vm_flags & VM_SHARED)
mapping_unmap_writable(file->f_mapping);
file = vma->vm_file;
+ uksm_vma_add_new(vma);
out:
perf_event_mmap(vma);
@@ -1882,6 +1901,7 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
if (vm_flags & VM_SHARED)
mapping_unmap_writable(file->f_mapping);
free_vma:
+ uksm_remove_vma(vma);
vm_area_free(vma);
unacct_error:
if (charged)
@@ -2742,6 +2762,8 @@ int __split_vma(struct mm_struct *mm, struct vm_area_struct *vma,
else
err = vma_adjust(vma, vma->vm_start, addr, vma->vm_pgoff, new);
+ uksm_vma_add_new(new);
+
/* Success. */
if (!err)
return 0;
@@ -3032,6 +3054,7 @@ static int do_brk_flags(unsigned long addr, unsigned long len, unsigned long fla
if ((flags & (~VM_EXEC)) != 0)
return -EINVAL;
flags |= VM_DATA_DEFAULT_FLAGS | VM_ACCOUNT | mm->def_flags;
+ uksm_vm_flags_mod(&flags);
mapped_addr = get_unmapped_area(NULL, addr, len, 0, MAP_FIXED);
if (IS_ERR_VALUE(mapped_addr))
@@ -3077,6 +3100,7 @@ static int do_brk_flags(unsigned long addr, unsigned long len, unsigned long fla
vma->vm_flags = flags;
vma->vm_page_prot = vm_get_page_prot(flags);
vma_link(mm, vma, prev, rb_link, rb_parent);
+ uksm_vma_add_new(vma);
out:
perf_event_mmap(vma);
mm->total_vm += len >> PAGE_SHIFT;
@@ -3153,6 +3177,11 @@ void exit_mmap(struct mm_struct *mm)
mmap_write_lock(mm);
mmap_write_unlock(mm);
}
+ /*
+ * Taking write lock on mmap does not harm others,
+ * but it's crucial for uksm to avoid races.
+ */
+ mmap_write_lock(mm);
if (mm->locked_vm)
unlock_range(mm->mmap, ULONG_MAX);
@@ -3183,6 +3212,11 @@ void exit_mmap(struct mm_struct *mm)
cond_resched();
}
vm_unacct_memory(nr_accounted);
+
+ mm->mmap = NULL;
+ mm->mm_rb = RB_ROOT;
+ vmacache_invalidate(mm);
+ mmap_write_unlock(mm);
}
/* Insert vm structure into process list sorted by address
@@ -3290,6 +3324,7 @@ struct vm_area_struct *copy_vma(struct vm_area_struct **vmap,
new_vma->vm_ops->open(new_vma);
vma_link(mm, new_vma, prev, rb_link, rb_parent);
*need_rmap_locks = false;
+ uksm_vma_add_new(new_vma);
}
return new_vma;
@@ -3454,6 +3489,7 @@ static struct vm_area_struct *__install_special_mapping(
vm_stat_account(mm, vma->vm_flags, len >> PAGE_SHIFT);
perf_event_mmap(vma);
+ uksm_vma_add_new(vma);
return vma;
diff --git a/mm/uksm.c b/mm/uksm.c
new file mode 100644
index 000000000..e4732c00b
--- /dev/null
+++ b/mm/uksm.c
@@ -0,0 +1,5614 @@
+/*
+ * Ultra KSM. Copyright (C) 2011-2012 Nai Xia
+ *
+ * This is an improvement upon KSM. Some basic data structures and routines
+ * are borrowed from ksm.c .
+ *
+ * Its new features:
+ * 1. Full system scan:
+ * It automatically scans all user processes' anonymous VMAs. Kernel-user
+ * interaction to submit a memory area to KSM is no longer needed.
+ *
+ * 2. Rich area detection:
+ * It automatically detects rich areas containing abundant duplicated
+ * pages based. Rich areas are given a full scan speed. Poor areas are
+ * sampled at a reasonable speed with very low CPU consumption.
+ *
+ * 3. Ultra Per-page scan speed improvement:
+ * A new hash algorithm is proposed. As a result, on a machine with
+ * Core(TM)2 Quad Q9300 CPU in 32-bit mode and 800MHZ DDR2 main memory, it
+ * can scan memory areas that does not contain duplicated pages at speed of
+ * 627MB/sec ~ 2445MB/sec and can merge duplicated areas at speed of
+ * 477MB/sec ~ 923MB/sec.
+ *
+ * 4. Thrashing area avoidance:
+ * Thrashing area(an VMA that has frequent Ksm page break-out) can be
+ * filtered out. My benchmark shows it's more efficient than KSM's per-page
+ * hash value based volatile page detection.
+ *
+ *
+ * 5. Misc changes upon KSM:
+ * * It has a fully x86-opitmized memcmp dedicated for 4-byte-aligned page
+ * comparison. It's much faster than default C version on x86.
+ * * rmap_item now has an struct *page member to loosely cache a
+ * address-->page mapping, which reduces too much time-costly
+ * follow_page().
+ * * The VMA creation/exit procedures are hooked to let the Ultra KSM know.
+ * * try_to_merge_two_pages() now can revert a pte if it fails. No break_
+ * ksm is needed for this case.
+ *
+ * 6. Full Zero Page consideration(contributed by Figo Zhang)
+ * Now uksmd consider full zero pages as special pages and merge them to an
+ * special unswappable uksm zero page.
+ */
+
+#include <linux/errno.h>
+#include <linux/mm.h>
+#include <linux/fs.h>
+#include <linux/mman.h>
+#include <linux/sched.h>
+#include <linux/sched/mm.h>
+#include <linux/sched/coredump.h>
+#include <linux/sched/cputime.h>
+#include <linux/rwsem.h>
+#include <linux/pagemap.h>
+#include <linux/rmap.h>
+#include <linux/spinlock.h>
+#include <linux/jhash.h>
+#include <linux/delay.h>
+#include <linux/kthread.h>
+#include <linux/wait.h>
+#include <linux/slab.h>
+#include <linux/rbtree.h>
+#include <linux/memory.h>
+#include <linux/mmu_notifier.h>
+#include <linux/swap.h>
+#include <linux/ksm.h>
+#include <linux/crypto.h>
+#include <linux/scatterlist.h>
+#include <crypto/hash.h>
+#include <linux/random.h>
+#include <linux/math64.h>
+#include <linux/gcd.h>
+#include <linux/freezer.h>
+#include <linux/oom.h>
+#include <linux/numa.h>
+#include <linux/sradix-tree.h>
+
+#include <asm/tlbflush.h>
+#include "internal.h"
+
+#ifdef CONFIG_X86
+#undef memcmp
+
+#ifdef CONFIG_X86_32
+#define memcmp memcmpx86_32
+/*
+ * Compare 4-byte-aligned address s1 and s2, with length n
+ */
+int memcmpx86_32(void *s1, void *s2, size_t n)
+{
+ size_t num = n / 4;
+ register int res;
+
+ __asm__ __volatile__
+ (
+ "testl %3,%3\n\t"
+ "repe; cmpsd\n\t"
+ "je 1f\n\t"
+ "sbbl %0,%0\n\t"
+ "orl $1,%0\n"
+ "1:"
+ : "=&a" (res), "+&S" (s1), "+&D" (s2), "+&c" (num)
+ : "0" (0)
+ : "cc");
+
+ return res;
+}
+
+/*
+ * Check the page is all zero ?
+ */
+static int is_full_zero(const void *s1, size_t len)
+{
+ unsigned char same;
+
+ len /= 4;
+
+ __asm__ __volatile__
+ ("repe; scasl;"
+ "sete %0"
+ : "=qm" (same), "+D" (s1), "+c" (len)
+ : "a" (0)
+ : "cc");
+
+ return same;
+}
+
+
+#elif defined(CONFIG_X86_64)
+#define memcmp memcmpx86_64
+/*
+ * Compare 8-byte-aligned address s1 and s2, with length n
+ */
+int memcmpx86_64(void *s1, void *s2, size_t n)
+{
+ size_t num = n / 8;
+ register int res;
+
+ __asm__ __volatile__
+ (
+ "testq %q3,%q3\n\t"
+ "repe; cmpsq\n\t"
+ "je 1f\n\t"
+ "sbbq %q0,%q0\n\t"
+ "orq $1,%q0\n"
+ "1:"
+ : "=&a" (res), "+&S" (s1), "+&D" (s2), "+&c" (num)
+ : "0" (0)
+ : "cc");
+
+ return res;
+}
+
+static int is_full_zero(const void *s1, size_t len)
+{
+ unsigned char same;
+
+ len /= 8;
+
+ __asm__ __volatile__
+ ("repe; scasq;"
+ "sete %0"
+ : "=qm" (same), "+D" (s1), "+c" (len)
+ : "a" (0)
+ : "cc");
+
+ return same;
+}
+
+#endif
+#else
+static int is_full_zero(const void *s1, size_t len)
+{
+ unsigned long *src = s1;
+ int i;
+
+ len /= sizeof(*src);
+
+ for (i = 0; i < len; i++) {
+ if (src[i])
+ return 0;
+ }
+
+ return 1;
+}
+#endif
+
+#define UKSM_RUNG_ROUND_FINISHED (1 << 0)
+#define TIME_RATIO_SCALE 10000
+
+#define SLOT_TREE_NODE_SHIFT 8
+#define SLOT_TREE_NODE_STORE_SIZE (1UL << SLOT_TREE_NODE_SHIFT)
+struct slot_tree_node {
+ unsigned long size;
+ struct sradix_tree_node snode;
+ void *stores[SLOT_TREE_NODE_STORE_SIZE];
+};
+
+static struct kmem_cache *slot_tree_node_cachep;
+
+static struct sradix_tree_node *slot_tree_node_alloc(void)
+{
+ struct slot_tree_node *p;
+
+ p = kmem_cache_zalloc(slot_tree_node_cachep, GFP_KERNEL |
+ __GFP_NORETRY | __GFP_NOWARN);
+ if (!p)
+ return NULL;
+
+ return &p->snode;
+}
+
+static void slot_tree_node_free(struct sradix_tree_node *node)
+{
+ struct slot_tree_node *p;
+
+ p = container_of(node, struct slot_tree_node, snode);
+ kmem_cache_free(slot_tree_node_cachep, p);
+}
+
+static void slot_tree_node_extend(struct sradix_tree_node *parent,
+ struct sradix_tree_node *child)
+{
+ struct slot_tree_node *p, *c;
+
+ p = container_of(parent, struct slot_tree_node, snode);
+ c = container_of(child, struct slot_tree_node, snode);
+
+ p->size += c->size;
+}
+
+void slot_tree_node_assign(struct sradix_tree_node *node,
+ unsigned int index, void *item)
+{
+ struct vma_slot *slot = item;
+ struct slot_tree_node *cur;
+
+ slot->snode = node;
+ slot->sindex = index;
+
+ while (node) {
+ cur = container_of(node, struct slot_tree_node, snode);
+ cur->size += slot->pages;
+ node = node->parent;
+ }
+}
+
+void slot_tree_node_rm(struct sradix_tree_node *node, unsigned int offset)
+{
+ struct vma_slot *slot;
+ struct slot_tree_node *cur;
+ unsigned long pages;
+
+ if (node->height == 1) {
+ slot = node->stores[offset];
+ pages = slot->pages;
+ } else {
+ cur = container_of(node->stores[offset],
+ struct slot_tree_node, snode);
+ pages = cur->size;
+ }
+
+ while (node) {
+ cur = container_of(node, struct slot_tree_node, snode);
+ cur->size -= pages;
+ node = node->parent;
+ }
+}
+
+unsigned long slot_iter_index;
+int slot_iter(void *item, unsigned long height)
+{
+ struct slot_tree_node *node;
+ struct vma_slot *slot;
+
+ if (height == 1) {
+ slot = item;
+ if (slot_iter_index < slot->pages) {
+ /*in this one*/
+ return 1;
+ } else {
+ slot_iter_index -= slot->pages;
+ return 0;
+ }
+
+ } else {
+ node = container_of(item, struct slot_tree_node, snode);
+ if (slot_iter_index < node->size) {
+ /*in this one*/
+ return 1;
+ } else {
+ slot_iter_index -= node->size;
+ return 0;
+ }
+ }
+}
+
+
+static inline void slot_tree_init_root(struct sradix_tree_root *root)
+{
+ init_sradix_tree_root(root, SLOT_TREE_NODE_SHIFT);
+ root->alloc = slot_tree_node_alloc;
+ root->free = slot_tree_node_free;
+ root->extend = slot_tree_node_extend;
+ root->assign = slot_tree_node_assign;
+ root->rm = slot_tree_node_rm;
+}
+
+void slot_tree_init(void)
+{
+ slot_tree_node_cachep = kmem_cache_create("slot_tree_node",
+ sizeof(struct slot_tree_node), 0,
+ SLAB_PANIC | SLAB_RECLAIM_ACCOUNT,
+ NULL);
+}
+
+
+/* Each rung of this ladder is a list of VMAs having a same scan ratio */
+struct scan_rung {
+ //struct list_head scanned_list;
+ struct sradix_tree_root vma_root;
+ struct sradix_tree_root vma_root2;
+
+ struct vma_slot *current_scan;
+ unsigned long current_offset;
+
+ /*
+ * The initial value for current_offset, it should loop over
+ * [0~ step - 1] to let all slot have its chance to be scanned.
+ */
+ unsigned long offset_init;
+ unsigned long step; /* dynamic step for current_offset */
+ unsigned int flags;
+ unsigned long pages_to_scan;
+ //unsigned long fully_scanned_slots;
+ /*
+ * a little bit tricky - if cpu_time_ratio > 0, then the value is the
+ * the cpu time ratio it can spend in rung_i for every scan
+ * period. if < 0, then it is the cpu time ratio relative to the
+ * max cpu percentage user specified. Both in unit of
+ * 1/TIME_RATIO_SCALE
+ */
+ int cpu_ratio;
+
+ /*
+ * How long it will take for all slots in this rung to be fully
+ * scanned? If it's zero, we don't care about the cover time:
+ * it's fully scanned.
+ */
+ unsigned int cover_msecs;
+ //unsigned long vma_num;
+ //unsigned long pages; /* Sum of all slot's pages in rung */
+};
+
+/**
+ * node of either the stable or unstale rbtree
+ *
+ */
+struct tree_node {
+ struct rb_node node; /* link in the main (un)stable rbtree */
+ struct rb_root sub_root; /* rb_root for sublevel collision rbtree */
+ u32 hash;
+ unsigned long count; /* TODO: merged with sub_root */
+ struct list_head all_list; /* all tree nodes in stable/unstable tree */
+};
+
+/**
+ * struct stable_node - node of the stable rbtree
+ * @node: rb node of this ksm page in the stable tree
+ * @hlist: hlist head of rmap_items using this ksm page
+ * @kpfn: page frame number of this ksm page
+ */
+struct stable_node {
+ struct rb_node node; /* link in sub-rbtree */
+ struct tree_node *tree_node; /* it's tree node root in stable tree, NULL if it's in hell list */
+ struct hlist_head hlist;
+ unsigned long kpfn;
+ u32 hash_max; /* if ==0 then it's not been calculated yet */
+ struct list_head all_list; /* in a list for all stable nodes */
+};
+
+/**
+ * struct node_vma - group rmap_items linked in a same stable
+ * node together.
+ */
+struct node_vma {
+ union {
+ struct vma_slot *slot;
+ unsigned long key; /* slot is used as key sorted on hlist */
+ };
+ struct hlist_node hlist;
+ struct hlist_head rmap_hlist;
+ struct stable_node *head;
+};
+
+/**
+ * struct rmap_item - reverse mapping item for virtual addresses
+ * @rmap_list: next rmap_item in mm_slot's singly-linked rmap_list
+ * @anon_vma: pointer to anon_vma for this mm,address, when in stable tree
+ * @mm: the memory structure this rmap_item is pointing into
+ * @address: the virtual address this rmap_item tracks (+ flags in low bits)
+ * @node: rb node of this rmap_item in the unstable tree
+ * @head: pointer to stable_node heading this list in the stable tree
+ * @hlist: link into hlist of rmap_items hanging off that stable_node
+ */
+struct rmap_item {
+ struct vma_slot *slot;
+ struct page *page;
+ unsigned long address; /* + low bits used for flags below */
+ unsigned long hash_round;
+ unsigned long entry_index;
+ union {
+ struct {/* when in unstable tree */
+ struct rb_node node;
+ struct tree_node *tree_node;
+ u32 hash_max;
+ };
+ struct { /* when in stable tree */
+ struct node_vma *head;
+ struct hlist_node hlist;
+ struct anon_vma *anon_vma;
+ };
+ };
+} __aligned(4);
+
+struct rmap_list_entry {
+ union {
+ struct rmap_item *item;
+ unsigned long addr;
+ };
+ /* lowest bit is used for is_addr tag */
+} __aligned(4); /* 4 aligned to fit in to pages*/
+
+
+/* Basic data structure definition ends */
+
+
+/*
+ * Flags for rmap_item to judge if it's listed in the stable/unstable tree.
+ * The flags use the low bits of rmap_item.address
+ */
+#define UNSTABLE_FLAG 0x1
+#define STABLE_FLAG 0x2
+#define get_rmap_addr(x) ((x)->address & PAGE_MASK)
+
+/*
+ * rmap_list_entry helpers
+ */
+#define IS_ADDR_FLAG 1
+#define is_addr(ptr) ((unsigned long)(ptr) & IS_ADDR_FLAG)
+#define set_is_addr(ptr) ((ptr) |= IS_ADDR_FLAG)
+#define get_clean_addr(ptr) (((ptr) & ~(__typeof__(ptr))IS_ADDR_FLAG))
+
+
+/*
+ * High speed caches for frequently allocated and freed structs
+ */
+static struct kmem_cache *rmap_item_cache;
+static struct kmem_cache *stable_node_cache;
+static struct kmem_cache *node_vma_cache;
+static struct kmem_cache *vma_slot_cache;
+static struct kmem_cache *tree_node_cache;
+#define UKSM_KMEM_CACHE(__struct, __flags) kmem_cache_create("uksm_"#__struct,\
+ sizeof(struct __struct), __alignof__(struct __struct),\
+ (__flags), NULL)
+
+/* Array of all scan_rung, uksm_scan_ladder[0] having the minimum scan ratio */
+#define SCAN_LADDER_SIZE 4
+static struct scan_rung uksm_scan_ladder[SCAN_LADDER_SIZE];
+
+/* The evaluation rounds uksmd has finished */
+static unsigned long long uksm_eval_round = 1;
+
+/*
+ * we add 1 to this var when we consider we should rebuild the whole
+ * unstable tree.
+ */
+static unsigned long uksm_hash_round = 1;
+
+/*
+ * How many times the whole memory is scanned.
+ */
+static unsigned long long fully_scanned_round = 1;
+
+/* The total number of virtual pages of all vma slots */
+static u64 uksm_pages_total;
+
+/* The number of pages has been scanned since the start up */
+static u64 uksm_pages_scanned;
+
+static u64 scanned_virtual_pages;
+
+/* The number of pages has been scanned since last encode_benefit call */
+static u64 uksm_pages_scanned_last;
+
+/* If the scanned number is tooo large, we encode it here */
+static u64 pages_scanned_stored;
+
+static unsigned long pages_scanned_base;
+
+/* The number of nodes in the stable tree */
+static unsigned long uksm_pages_shared;
+
+/* The number of page slots additionally sharing those nodes */
+static unsigned long uksm_pages_sharing;
+
+/* The number of nodes in the unstable tree */
+static unsigned long uksm_pages_unshared;
+
+/*
+ * Milliseconds ksmd should sleep between scans,
+ * >= 100ms to be consistent with
+ * scan_time_to_sleep_msec()
+ */
+static unsigned int uksm_sleep_jiffies;
+
+/* The real value for the uksmd next sleep */
+static unsigned int uksm_sleep_real;
+
+/* Saved value for user input uksm_sleep_jiffies when it's enlarged */
+static unsigned int uksm_sleep_saved;
+
+/* Max percentage of cpu utilization ksmd can take to scan in one batch */
+static unsigned int uksm_max_cpu_percentage;
+
+static int uksm_cpu_governor;
+
+static char *uksm_cpu_governor_str[4] = { "full", "medium", "low", "quiet" };
+
+struct uksm_cpu_preset_s {
+ int cpu_ratio[SCAN_LADDER_SIZE];
+ unsigned int cover_msecs[SCAN_LADDER_SIZE];
+ unsigned int max_cpu; /* percentage */
+};
+
+struct uksm_cpu_preset_s uksm_cpu_preset[4] = {
+ { {20, 40, -2500, -10000}, {1000, 500, 200, 50}, 95},
+ { {20, 30, -2500, -10000}, {1000, 500, 400, 100}, 50},
+ { {10, 20, -5000, -10000}, {1500, 1000, 1000, 250}, 20},
+ { {10, 20, 40, 75}, {2000, 1000, 1000, 1000}, 1},
+};
+
+/* The default value for uksm_ema_page_time if it's not initialized */
+#define UKSM_PAGE_TIME_DEFAULT 500
+
+/*cost to scan one page by expotional moving average in nsecs */
+static unsigned long uksm_ema_page_time = UKSM_PAGE_TIME_DEFAULT;
+
+/* The expotional moving average alpha weight, in percentage. */
+#define EMA_ALPHA 20
+
+/*
+ * The threshold used to filter out thrashing areas,
+ * If it == 0, filtering is disabled, otherwise it's the percentage up-bound
+ * of the thrashing ratio of all areas. Any area with a bigger thrashing ratio
+ * will be considered as having a zero duplication ratio.
+ */
+static unsigned int uksm_thrash_threshold = 50;
+
+/* How much dedup ratio is considered to be abundant*/
+static unsigned int uksm_abundant_threshold = 10;
+
+/* All slots having merged pages in this eval round. */
+struct list_head vma_slot_dedup = LIST_HEAD_INIT(vma_slot_dedup);
+
+/* How many times the ksmd has slept since startup */
+static unsigned long long uksm_sleep_times;
+
+#define UKSM_RUN_STOP 0
+#define UKSM_RUN_MERGE 1
+static unsigned int uksm_run = 1;
+
+static DECLARE_WAIT_QUEUE_HEAD(uksm_thread_wait);
+static DEFINE_MUTEX(uksm_thread_mutex);
+
+/*
+ * List vma_slot_new is for newly created vma_slot waiting to be added by
+ * ksmd. If one cannot be added(e.g. due to it's too small), it's moved to
+ * vma_slot_noadd. vma_slot_del is the list for vma_slot whose corresponding
+ * VMA has been removed/freed.
+ */
+struct list_head vma_slot_new = LIST_HEAD_INIT(vma_slot_new);
+struct list_head vma_slot_noadd = LIST_HEAD_INIT(vma_slot_noadd);
+struct list_head vma_slot_del = LIST_HEAD_INIT(vma_slot_del);
+static DEFINE_SPINLOCK(vma_slot_list_lock);
+
+/* The unstable tree heads */
+static struct rb_root root_unstable_tree = RB_ROOT;
+
+/*
+ * All tree_nodes are in a list to be freed at once when unstable tree is
+ * freed after each scan round.
+ */
+static struct list_head unstable_tree_node_list =
+ LIST_HEAD_INIT(unstable_tree_node_list);
+
+/* List contains all stable nodes */
+static struct list_head stable_node_list = LIST_HEAD_INIT(stable_node_list);
+
+/*
+ * When the hash strength is changed, the stable tree must be delta_hashed and
+ * re-structured. We use two set of below structs to speed up the
+ * re-structuring of stable tree.
+ */
+static struct list_head
+stable_tree_node_list[2] = {LIST_HEAD_INIT(stable_tree_node_list[0]),
+ LIST_HEAD_INIT(stable_tree_node_list[1])};
+
+static struct list_head *stable_tree_node_listp = &stable_tree_node_list[0];
+static struct rb_root root_stable_tree[2] = {RB_ROOT, RB_ROOT};
+static struct rb_root *root_stable_treep = &root_stable_tree[0];
+static unsigned long stable_tree_index;
+
+/* The hash strength needed to hash a full page */
+#define HASH_STRENGTH_FULL (PAGE_SIZE / sizeof(u32))
+
+/* The hash strength needed for loop-back hashing */
+#define HASH_STRENGTH_MAX (HASH_STRENGTH_FULL + 10)
+
+/* The random offsets in a page */
+static u32 *random_nums;
+
+/* The hash strength */
+static unsigned long hash_strength = HASH_STRENGTH_FULL >> 4;
+
+/* The delta value each time the hash strength increases or decreases */
+static unsigned long hash_strength_delta;
+#define HASH_STRENGTH_DELTA_MAX 5
+
+/* The time we have saved due to random_sample_hash */
+static u64 rshash_pos;
+
+/* The time we have wasted due to hash collision */
+static u64 rshash_neg;
+
+struct uksm_benefit {
+ u64 pos;
+ u64 neg;
+ u64 scanned;
+ unsigned long base;
+} benefit;
+
+/*
+ * The relative cost of memcmp, compared to 1 time unit of random sample
+ * hash, this value is tested when ksm module is initialized
+ */
+static unsigned long memcmp_cost;
+
+static unsigned long rshash_neg_cont_zero;
+static unsigned long rshash_cont_obscure;
+
+/* The possible states of hash strength adjustment heuristic */
+enum rshash_states {
+ RSHASH_STILL,
+ RSHASH_TRYUP,
+ RSHASH_TRYDOWN,
+ RSHASH_NEW,
+ RSHASH_PRE_STILL,
+};
+
+/* The possible direction we are about to adjust hash strength */
+enum rshash_direct {
+ GO_UP,
+ GO_DOWN,
+ OBSCURE,
+ STILL,
+};
+
+/* random sampling hash state machine */
+static struct {
+ enum rshash_states state;
+ enum rshash_direct pre_direct;
+ u8 below_count;
+ /* Keep a lookup window of size 5, iff above_count/below_count > 3
+ * in this window we stop trying.
+ */
+ u8 lookup_window_index;
+ u64 stable_benefit;
+ unsigned long turn_point_down;
+ unsigned long turn_benefit_down;
+ unsigned long turn_point_up;
+ unsigned long turn_benefit_up;
+ unsigned long stable_point;
+} rshash_state;
+
+/*zero page hash table, hash_strength [0 ~ HASH_STRENGTH_MAX]*/
+static u32 *zero_hash_table;
+
+static inline struct node_vma *alloc_node_vma(void)
+{
+ struct node_vma *node_vma;
+
+ node_vma = kmem_cache_zalloc(node_vma_cache, GFP_KERNEL |
+ __GFP_NORETRY | __GFP_NOWARN);
+ if (node_vma) {
+ INIT_HLIST_HEAD(&node_vma->rmap_hlist);
+ INIT_HLIST_NODE(&node_vma->hlist);
+ }
+ return node_vma;
+}
+
+static inline void free_node_vma(struct node_vma *node_vma)
+{
+ kmem_cache_free(node_vma_cache, node_vma);
+}
+
+
+static inline struct vma_slot *alloc_vma_slot(void)
+{
+ struct vma_slot *slot;
+
+ /*
+ * In case ksm is not initialized by now.
+ * Oops, we need to consider the call site of uksm_init() in the future.
+ */
+ if (!vma_slot_cache)
+ return NULL;
+
+ slot = kmem_cache_zalloc(vma_slot_cache, GFP_KERNEL |
+ __GFP_NORETRY | __GFP_NOWARN);
+ if (slot) {
+ INIT_LIST_HEAD(&slot->slot_list);
+ INIT_LIST_HEAD(&slot->dedup_list);
+ slot->flags |= UKSM_SLOT_NEED_RERAND;
+ }
+ return slot;
+}
+
+static inline void free_vma_slot(struct vma_slot *vma_slot)
+{
+ kmem_cache_free(vma_slot_cache, vma_slot);
+}
+
+
+
+static inline struct rmap_item *alloc_rmap_item(void)
+{
+ struct rmap_item *rmap_item;
+
+ rmap_item = kmem_cache_zalloc(rmap_item_cache, GFP_KERNEL |
+ __GFP_NORETRY | __GFP_NOWARN);
+ if (rmap_item) {
+ /* bug on lowest bit is not clear for flag use */
+ BUG_ON(is_addr(rmap_item));
+ }
+ return rmap_item;
+}
+
+static inline void free_rmap_item(struct rmap_item *rmap_item)
+{
+ rmap_item->slot = NULL; /* debug safety */
+ kmem_cache_free(rmap_item_cache, rmap_item);
+}
+
+static inline struct stable_node *alloc_stable_node(void)
+{
+ struct stable_node *node;
+
+ node = kmem_cache_alloc(stable_node_cache, GFP_KERNEL |
+ __GFP_NORETRY | __GFP_NOWARN);
+ if (!node)
+ return NULL;
+
+ INIT_HLIST_HEAD(&node->hlist);
+ list_add(&node->all_list, &stable_node_list);
+ return node;
+}
+
+static inline void free_stable_node(struct stable_node *stable_node)
+{
+ list_del(&stable_node->all_list);
+ kmem_cache_free(stable_node_cache, stable_node);
+}
+
+static inline struct tree_node *alloc_tree_node(struct list_head *list)
+{
+ struct tree_node *node;
+
+ node = kmem_cache_zalloc(tree_node_cache, GFP_KERNEL |
+ __GFP_NORETRY | __GFP_NOWARN);
+ if (!node)
+ return NULL;
+
+ list_add(&node->all_list, list);
+ return node;
+}
+
+static inline void free_tree_node(struct tree_node *node)
+{
+ list_del(&node->all_list);
+ kmem_cache_free(tree_node_cache, node);
+}
+
+static void uksm_drop_anon_vma(struct rmap_item *rmap_item)
+{
+ struct anon_vma *anon_vma = rmap_item->anon_vma;
+
+ put_anon_vma(anon_vma);
+}
+
+
+/**
+ * Remove a stable node from stable_tree, may unlink from its tree_node and
+ * may remove its parent tree_node if no other stable node is pending.
+ *
+ * @stable_node The node need to be removed
+ * @unlink_rb Will this node be unlinked from the rbtree?
+ * @remove_tree_ node Will its tree_node be removed if empty?
+ */
+static void remove_node_from_stable_tree(struct stable_node *stable_node,
+ int unlink_rb, int remove_tree_node)
+{
+ struct node_vma *node_vma;
+ struct rmap_item *rmap_item;
+ struct hlist_node *n;
+
+ if (!hlist_empty(&stable_node->hlist)) {
+ hlist_for_each_entry_safe(node_vma, n,
+ &stable_node->hlist, hlist) {
+ hlist_for_each_entry(rmap_item, &node_vma->rmap_hlist, hlist) {
+ uksm_pages_sharing--;
+
+ uksm_drop_anon_vma(rmap_item);
+ rmap_item->address &= PAGE_MASK;
+ }
+ free_node_vma(node_vma);
+ cond_resched();
+ }
+
+ /* the last one is counted as shared */
+ uksm_pages_shared--;
+ uksm_pages_sharing++;
+ }
+
+ if (stable_node->tree_node && unlink_rb) {
+ rb_erase(&stable_node->node,
+ &stable_node->tree_node->sub_root);
+
+ if (RB_EMPTY_ROOT(&stable_node->tree_node->sub_root) &&
+ remove_tree_node) {
+ rb_erase(&stable_node->tree_node->node,
+ root_stable_treep);
+ free_tree_node(stable_node->tree_node);
+ } else {
+ stable_node->tree_node->count--;
+ }
+ }
+
+ free_stable_node(stable_node);
+}
+
+
+/*
+ * get_uksm_page: checks if the page indicated by the stable node
+ * is still its ksm page, despite having held no reference to it.
+ * In which case we can trust the content of the page, and it
+ * returns the gotten page; but if the page has now been zapped,
+ * remove the stale node from the stable tree and return NULL.
+ *
+ * You would expect the stable_node to hold a reference to the ksm page.
+ * But if it increments the page's count, swapping out has to wait for
+ * ksmd to come around again before it can free the page, which may take
+ * seconds or even minutes: much too unresponsive. So instead we use a
+ * "keyhole reference": access to the ksm page from the stable node peeps
+ * out through its keyhole to see if that page still holds the right key,
+ * pointing back to this stable node. This relies on freeing a PageAnon
+ * page to reset its page->mapping to NULL, and relies on no other use of
+ * a page to put something that might look like our key in page->mapping.
+ *
+ * include/linux/pagemap.h page_cache_get_speculative() is a good reference,
+ * but this is different - made simpler by uksm_thread_mutex being held, but
+ * interesting for assuming that no other use of the struct page could ever
+ * put our expected_mapping into page->mapping (or a field of the union which
+ * coincides with page->mapping). The RCU calls are not for KSM at all, but
+ * to keep the page_count protocol described with page_cache_get_speculative.
+ *
+ * Note: it is possible that get_uksm_page() will return NULL one moment,
+ * then page the next, if the page is in between page_freeze_refs() and
+ * page_unfreeze_refs(): this shouldn't be a problem anywhere, the page
+ * is on its way to being freed; but it is an anomaly to bear in mind.
+ *
+ * @unlink_rb: if the removal of this node will firstly unlink from
+ * its rbtree. stable_node_reinsert will prevent this when restructuring the
+ * node from its old tree.
+ *
+ * @remove_tree_node: if this is the last one of its tree_node, will the
+ * tree_node be freed ? If we are inserting stable node, this tree_node may
+ * be reused, so don't free it.
+ */
+static struct page *get_uksm_page(struct stable_node *stable_node,
+ int unlink_rb, int remove_tree_node)
+{
+ struct page *page;
+ void *expected_mapping;
+ unsigned long kpfn;
+
+ expected_mapping = (void *)((unsigned long)stable_node |
+ PAGE_MAPPING_KSM);
+again:
+ kpfn = READ_ONCE(stable_node->kpfn);
+ page = pfn_to_page(kpfn);
+
+ /*
+ * page is computed from kpfn, so on most architectures reading
+ * page->mapping is naturally ordered after reading node->kpfn,
+ * but on Alpha we need to be more careful.
+ */
+ smp_rmb();
+
+ if (READ_ONCE(page->mapping) != expected_mapping)
+ goto stale;
+
+ /*
+ * We cannot do anything with the page while its refcount is 0.
+ * Usually 0 means free, or tail of a higher-order page: in which
+ * case this node is no longer referenced, and should be freed;
+ * however, it might mean that the page is under page_freeze_refs().
+ * The __remove_mapping() case is easy, again the node is now stale;
+ * but if page is swapcache in migrate_page_move_mapping(), it might
+ * still be our page, in which case it's essential to keep the node.
+ */
+ while (!get_page_unless_zero(page)) {
+ /*
+ * Another check for page->mapping != expected_mapping would
+ * work here too. We have chosen the !PageSwapCache test to
+ * optimize the common case, when the page is or is about to
+ * be freed: PageSwapCache is cleared (under spin_lock_irq)
+ * in the freeze_refs section of __remove_mapping(); but Anon
+ * page->mapping reset to NULL later, in free_pages_prepare().
+ */
+ if (!PageSwapCache(page))
+ goto stale;
+ cpu_relax();
+ }
+
+ if (READ_ONCE(page->mapping) != expected_mapping) {
+ put_page(page);
+ goto stale;
+ }
+
+ lock_page(page);
+ if (READ_ONCE(page->mapping) != expected_mapping) {
+ unlock_page(page);
+ put_page(page);
+ goto stale;
+ }
+ unlock_page(page);
+ return page;
+stale:
+ /*
+ * We come here from above when page->mapping or !PageSwapCache
+ * suggests that the node is stale; but it might be under migration.
+ * We need smp_rmb(), matching the smp_wmb() in ksm_migrate_page(),
+ * before checking whether node->kpfn has been changed.
+ */
+ smp_rmb();
+ if (stable_node->kpfn != kpfn)
+ goto again;
+
+ remove_node_from_stable_tree(stable_node, unlink_rb, remove_tree_node);
+
+ return NULL;
+}
+
+/*
+ * Removing rmap_item from stable or unstable tree.
+ * This function will clean the information from the stable/unstable tree.
+ */
+static inline void remove_rmap_item_from_tree(struct rmap_item *rmap_item)
+{
+ if (rmap_item->address & STABLE_FLAG) {
+ struct stable_node *stable_node;
+ struct node_vma *node_vma;
+ struct page *page;
+
+ node_vma = rmap_item->head;
+ stable_node = node_vma->head;
+ page = get_uksm_page(stable_node, 1, 1);
+ if (!page)
+ goto out;
+
+ /*
+ * page lock is needed because it's racing with
+ * try_to_unmap_ksm(), etc.
+ */
+ lock_page(page);
+ hlist_del(&rmap_item->hlist);
+
+ if (hlist_empty(&node_vma->rmap_hlist)) {
+ hlist_del(&node_vma->hlist);
+ free_node_vma(node_vma);
+ }
+ unlock_page(page);
+
+ put_page(page);
+ if (hlist_empty(&stable_node->hlist)) {
+ /* do NOT call remove_node_from_stable_tree() here,
+ * it's possible for a forked rmap_item not in
+ * stable tree while the in-tree rmap_items were
+ * deleted.
+ */
+ uksm_pages_shared--;
+ } else
+ uksm_pages_sharing--;
+
+
+ uksm_drop_anon_vma(rmap_item);
+ } else if (rmap_item->address & UNSTABLE_FLAG) {
+ if (rmap_item->hash_round == uksm_hash_round) {
+
+ rb_erase(&rmap_item->node,
+ &rmap_item->tree_node->sub_root);
+ if (RB_EMPTY_ROOT(&rmap_item->tree_node->sub_root)) {
+ rb_erase(&rmap_item->tree_node->node,
+ &root_unstable_tree);
+
+ free_tree_node(rmap_item->tree_node);
+ } else
+ rmap_item->tree_node->count--;
+ }
+ uksm_pages_unshared--;
+ }
+
+ rmap_item->address &= PAGE_MASK;
+ rmap_item->hash_max = 0;
+
+out:
+ cond_resched(); /* we're called from many long loops */
+}
+
+static inline int slot_in_uksm(struct vma_slot *slot)
+{
+ return list_empty(&slot->slot_list);
+}
+
+/*
+ * Test if the mm is exiting
+ */
+static inline bool uksm_test_exit(struct mm_struct *mm)
+{
+ return atomic_read(&mm->mm_users) == 0;
+}
+
+static inline unsigned long vma_pool_size(struct vma_slot *slot)
+{
+ return round_up(sizeof(struct rmap_list_entry) * slot->pages,
+ PAGE_SIZE) >> PAGE_SHIFT;
+}
+
+#define CAN_OVERFLOW_U64(x, delta) (U64_MAX - (x) < (delta))
+
+/* must be done with sem locked */
+static int slot_pool_alloc(struct vma_slot *slot)
+{
+ unsigned long pool_size;
+
+ if (slot->rmap_list_pool)
+ return 0;
+
+ pool_size = vma_pool_size(slot);
+ slot->rmap_list_pool = kcalloc(pool_size, sizeof(struct page *),
+ GFP_KERNEL);
+ if (!slot->rmap_list_pool)
+ return -ENOMEM;
+
+ slot->pool_counts = kcalloc(pool_size, sizeof(unsigned int),
+ GFP_KERNEL);
+ if (!slot->pool_counts) {
+ kfree(slot->rmap_list_pool);
+ return -ENOMEM;
+ }
+
+ slot->pool_size = pool_size;
+ BUG_ON(CAN_OVERFLOW_U64(uksm_pages_total, slot->pages));
+ slot->flags |= UKSM_SLOT_IN_UKSM;
+ uksm_pages_total += slot->pages;
+
+ return 0;
+}
+
+/*
+ * Called after vma is unlinked from its mm
+ */
+void uksm_remove_vma(struct vm_area_struct *vma)
+{
+ struct vma_slot *slot;
+
+ if (!vma->uksm_vma_slot)
+ return;
+
+ spin_lock(&vma_slot_list_lock);
+ slot = vma->uksm_vma_slot;
+ if (!slot)
+ goto out;
+
+ if (slot_in_uksm(slot)) {
+ /**
+ * This slot has been added by ksmd, so move to the del list
+ * waiting ksmd to free it.
+ */
+ list_add_tail(&slot->slot_list, &vma_slot_del);
+ } else {
+ /**
+ * It's still on new list. It's ok to free slot directly.
+ */
+ list_del(&slot->slot_list);
+ free_vma_slot(slot);
+ }
+out:
+ vma->uksm_vma_slot = NULL;
+ spin_unlock(&vma_slot_list_lock);
+}
+
+/**
+ * Need to do two things:
+ * 1. check if slot was moved to del list
+ * 2. make sure the mmap_sem is manipulated under valid vma.
+ *
+ * My concern here is that in some cases, this may make
+ * vma_slot_list_lock() waiters to serialized further by some
+ * sem->wait_lock, can this really be expensive?
+ *
+ *
+ * @return
+ * 0: if successfully locked mmap_sem
+ * -ENOENT: this slot was moved to del list
+ * -EBUSY: vma lock failed
+ */
+static int try_down_read_slot_mmap_sem(struct vma_slot *slot)
+{
+ struct vm_area_struct *vma;
+ struct mm_struct *mm;
+ struct rw_semaphore *sem;
+
+ spin_lock(&vma_slot_list_lock);
+
+ /* the slot_list was removed and inited from new list, when it enters
+ * uksm_list. If now it's not empty, then it must be moved to del list
+ */
+ if (!slot_in_uksm(slot)) {
+ spin_unlock(&vma_slot_list_lock);
+ return -ENOENT;
+ }
+
+ BUG_ON(slot->pages != vma_pages(slot->vma));
+ /* Ok, vma still valid */
+ vma = slot->vma;
+ mm = vma->vm_mm;
+ sem = &mm->mmap_lock;
+
+ if (uksm_test_exit(mm)) {
+ spin_unlock(&vma_slot_list_lock);
+ return -ENOENT;
+ }
+
+ if (down_read_trylock(sem)) {
+ spin_unlock(&vma_slot_list_lock);
+ if (slot_pool_alloc(slot)) {
+ uksm_remove_vma(vma);
+ up_read(sem);
+ return -ENOENT;
+ }
+ return 0;
+ }
+
+ spin_unlock(&vma_slot_list_lock);
+ return -EBUSY;
+}
+
+static inline unsigned long
+vma_page_address(struct page *page, struct vm_area_struct *vma)
+{
+ pgoff_t pgoff = page->index;
+ unsigned long address;
+
+ address = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
+ if (unlikely(address < vma->vm_start || address >= vma->vm_end)) {
+ /* page should be within @vma mapping range */
+ return -EFAULT;
+ }
+ return address;
+}
+
+
+/* return 0 on success with the item's mmap_sem locked */
+static inline int get_mergeable_page_lock_mmap(struct rmap_item *item)
+{
+ struct mm_struct *mm;
+ struct vma_slot *slot = item->slot;
+ int err = -EINVAL;
+
+ struct page *page;
+
+ /*
+ * try_down_read_slot_mmap_sem() returns non-zero if the slot
+ * has been removed by uksm_remove_vma().
+ */
+ if (try_down_read_slot_mmap_sem(slot))
+ return -EBUSY;
+
+ mm = slot->vma->vm_mm;
+
+ if (uksm_test_exit(mm))
+ goto failout_up;
+
+ page = item->page;
+ rcu_read_lock();
+ if (!get_page_unless_zero(page)) {
+ rcu_read_unlock();
+ goto failout_up;
+ }
+
+ /* No need to consider huge page here. */
+ if (item->slot->vma->anon_vma != page_anon_vma(page) ||
+ vma_page_address(page, item->slot->vma) != get_rmap_addr(item)) {
+ /*
+ * TODO:
+ * should we release this item becase of its stale page
+ * mapping?
+ */
+ put_page(page);
+ rcu_read_unlock();
+ goto failout_up;
+ }
+ rcu_read_unlock();
+ return 0;
+
+failout_up:
+ mmap_read_unlock(mm);
+ return err;
+}
+
+/*
+ * What kind of VMA is considered ?
+ */
+static inline int vma_can_enter(struct vm_area_struct *vma)
+{
+ return uksm_flags_can_scan(vma->vm_flags);
+}
+
+/*
+ * Called whenever a fresh new vma is created A new vma_slot.
+ * is created and inserted into a global list Must be called.
+ * after vma is inserted to its mm.
+ */
+void uksm_vma_add_new(struct vm_area_struct *vma)
+{
+ struct vma_slot *slot;
+
+ if (!vma_can_enter(vma)) {
+ vma->uksm_vma_slot = NULL;
+ return;
+ }
+
+ slot = alloc_vma_slot();
+ if (!slot) {
+ vma->uksm_vma_slot = NULL;
+ return;
+ }
+
+ vma->uksm_vma_slot = slot;
+ vma->vm_flags |= VM_MERGEABLE;
+ slot->vma = vma;
+ slot->mm = vma->vm_mm;
+ slot->ctime_j = jiffies;
+ slot->pages = vma_pages(vma);
+ spin_lock(&vma_slot_list_lock);
+ list_add_tail(&slot->slot_list, &vma_slot_new);
+ spin_unlock(&vma_slot_list_lock);
+}
+
+/* 32/3 < they < 32/2 */
+#define shiftl 8
+#define shiftr 12
+
+#define HASH_FROM_TO(from, to) \
+for (index = from; index < to; index++) { \
+ pos = random_nums[index]; \
+ hash += key[pos]; \
+ hash += (hash << shiftl); \
+ hash ^= (hash >> shiftr); \
+}
+
+
+#define HASH_FROM_DOWN_TO(from, to) \
+for (index = from - 1; index >= to; index--) { \
+ hash ^= (hash >> shiftr); \
+ hash ^= (hash >> (shiftr*2)); \
+ hash -= (hash << shiftl); \
+ hash += (hash << (shiftl*2)); \
+ pos = random_nums[index]; \
+ hash -= key[pos]; \
+}
+
+/*
+ * The main random sample hash function.
+ */
+static u32 random_sample_hash(void *addr, u32 hash_strength)
+{
+ u32 hash = 0xdeadbeef;
+ int index, pos, loop = hash_strength;
+ u32 *key = (u32 *)addr;
+
+ if (loop > HASH_STRENGTH_FULL)
+ loop = HASH_STRENGTH_FULL;
+
+ HASH_FROM_TO(0, loop);
+
+ if (hash_strength > HASH_STRENGTH_FULL) {
+ loop = hash_strength - HASH_STRENGTH_FULL;
+ HASH_FROM_TO(0, loop);
+ }
+
+ return hash;
+}
+
+
+/**
+ * It's used when hash strength is adjusted
+ *
+ * @addr The page's virtual address
+ * @from The original hash strength
+ * @to The hash strength changed to
+ * @hash The hash value generated with "from" hash value
+ *
+ * return the hash value
+ */
+static u32 delta_hash(void *addr, int from, int to, u32 hash)
+{
+ u32 *key = (u32 *)addr;
+ int index, pos; /* make sure they are int type */
+
+ if (to > from) {
+ if (from >= HASH_STRENGTH_FULL) {
+ from -= HASH_STRENGTH_FULL;
+ to -= HASH_STRENGTH_FULL;
+ HASH_FROM_TO(from, to);
+ } else if (to <= HASH_STRENGTH_FULL) {
+ HASH_FROM_TO(from, to);
+ } else {
+ HASH_FROM_TO(from, HASH_STRENGTH_FULL);
+ HASH_FROM_TO(0, to - HASH_STRENGTH_FULL);
+ }
+ } else {
+ if (from <= HASH_STRENGTH_FULL) {
+ HASH_FROM_DOWN_TO(from, to);
+ } else if (to >= HASH_STRENGTH_FULL) {
+ from -= HASH_STRENGTH_FULL;
+ to -= HASH_STRENGTH_FULL;
+ HASH_FROM_DOWN_TO(from, to);
+ } else {
+ HASH_FROM_DOWN_TO(from - HASH_STRENGTH_FULL, 0);
+ HASH_FROM_DOWN_TO(HASH_STRENGTH_FULL, to);
+ }
+ }
+
+ return hash;
+}
+
+/**
+ *
+ * Called when: rshash_pos or rshash_neg is about to overflow or a scan round
+ * has finished.
+ *
+ * return 0 if no page has been scanned since last call, 1 otherwise.
+ */
+static inline int encode_benefit(void)
+{
+ u64 scanned_delta, pos_delta, neg_delta;
+ unsigned long base = benefit.base;
+
+ scanned_delta = uksm_pages_scanned - uksm_pages_scanned_last;
+
+ if (!scanned_delta)
+ return 0;
+
+ scanned_delta >>= base;
+ pos_delta = rshash_pos >> base;
+ neg_delta = rshash_neg >> base;
+
+ if (CAN_OVERFLOW_U64(benefit.pos, pos_delta) ||
+ CAN_OVERFLOW_U64(benefit.neg, neg_delta) ||
+ CAN_OVERFLOW_U64(benefit.scanned, scanned_delta)) {
+ benefit.scanned >>= 1;
+ benefit.neg >>= 1;
+ benefit.pos >>= 1;
+ benefit.base++;
+ scanned_delta >>= 1;
+ pos_delta >>= 1;
+ neg_delta >>= 1;
+ }
+
+ benefit.pos += pos_delta;
+ benefit.neg += neg_delta;
+ benefit.scanned += scanned_delta;
+
+ BUG_ON(!benefit.scanned);
+
+ rshash_pos = rshash_neg = 0;
+ uksm_pages_scanned_last = uksm_pages_scanned;
+
+ return 1;
+}
+
+static inline void reset_benefit(void)
+{
+ benefit.pos = 0;
+ benefit.neg = 0;
+ benefit.base = 0;
+ benefit.scanned = 0;
+}
+
+static inline void inc_rshash_pos(unsigned long delta)
+{
+ if (CAN_OVERFLOW_U64(rshash_pos, delta))
+ encode_benefit();
+
+ rshash_pos += delta;
+}
+
+static inline void inc_rshash_neg(unsigned long delta)
+{
+ if (CAN_OVERFLOW_U64(rshash_neg, delta))
+ encode_benefit();
+
+ rshash_neg += delta;
+}
+
+
+static inline u32 page_hash(struct page *page, unsigned long hash_strength,
+ int cost_accounting)
+{
+ u32 val;
+ unsigned long delta;
+
+ void *addr = kmap_atomic(page);
+
+ val = random_sample_hash(addr, hash_strength);
+ kunmap_atomic(addr);
+
+ if (cost_accounting) {
+ if (hash_strength < HASH_STRENGTH_FULL)
+ delta = HASH_STRENGTH_FULL - hash_strength;
+ else
+ delta = 0;
+
+ inc_rshash_pos(delta);
+ }
+
+ return val;
+}
+
+static int memcmp_pages_with_cost(struct page *page1, struct page *page2,
+ int cost_accounting)
+{
+ char *addr1, *addr2;
+ int ret;
+
+ addr1 = kmap_atomic(page1);
+ addr2 = kmap_atomic(page2);
+ ret = memcmp(addr1, addr2, PAGE_SIZE);
+ kunmap_atomic(addr2);
+ kunmap_atomic(addr1);
+
+ if (cost_accounting)
+ inc_rshash_neg(memcmp_cost);
+
+ return ret;
+}
+
+static inline int pages_identical_with_cost(struct page *page1, struct page *page2)
+{
+ return !memcmp_pages_with_cost(page1, page2, 0);
+}
+
+static inline int is_page_full_zero(struct page *page)
+{
+ char *addr;
+ int ret;
+
+ addr = kmap_atomic(page);
+ ret = is_full_zero(addr, PAGE_SIZE);
+ kunmap_atomic(addr);
+
+ return ret;
+}
+
+static int write_protect_page(struct vm_area_struct *vma, struct page *page,
+ pte_t *orig_pte, pte_t *old_pte)
+{
+ struct mm_struct *mm = vma->vm_mm;
+ struct page_vma_mapped_walk pvmw = {
+ .page = page,
+ .vma = vma,
+ };
+ struct mmu_notifier_range range;
+ int swapped;
+ int err = -EFAULT;
+
+ pvmw.address = page_address_in_vma(page, vma);
+ if (pvmw.address == -EFAULT)
+ goto out;
+
+ BUG_ON(PageTransCompound(page));
+
+ mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, mm, pvmw.address,
+ pvmw.address + PAGE_SIZE);
+ mmu_notifier_invalidate_range_start(&range);
+
+ if (!page_vma_mapped_walk(&pvmw))
+ goto out_mn;
+ if (WARN_ONCE(!pvmw.pte, "Unexpected PMD mapping?"))
+ goto out_unlock;
+
+ if (old_pte)
+ *old_pte = *pvmw.pte;
+
+ if (pte_write(*pvmw.pte) || pte_dirty(*pvmw.pte) ||
+ (pte_protnone(*pvmw.pte) && pte_savedwrite(*pvmw.pte)) || mm_tlb_flush_pending(mm)) {
+ pte_t entry;
+
+ swapped = PageSwapCache(page);
+ flush_cache_page(vma, pvmw.address, page_to_pfn(page));
+ /*
+ * Ok this is tricky, when get_user_pages_fast() run it doesn't
+ * take any lock, therefore the check that we are going to make
+ * with the pagecount against the mapcount is racey and
+ * O_DIRECT can happen right after the check.
+ * So we clear the pte and flush the tlb before the check
+ * this assure us that no O_DIRECT can happen after the check
+ * or in the middle of the check.
+ */
+ entry = ptep_clear_flush_notify(vma, pvmw.address, pvmw.pte);
+ /*
+ * Check that no O_DIRECT or similar I/O is in progress on the
+ * page
+ */
+ if (page_mapcount(page) + 1 + swapped != page_count(page)) {
+ set_pte_at(mm, pvmw.address, pvmw.pte, entry);
+ goto out_unlock;
+ }
+ if (pte_dirty(entry))
+ set_page_dirty(page);
+
+ if (pte_protnone(entry))
+ entry = pte_mkclean(pte_clear_savedwrite(entry));
+ else
+ entry = pte_mkclean(pte_wrprotect(entry));
+
+ set_pte_at_notify(mm, pvmw.address, pvmw.pte, entry);
+ }
+ *orig_pte = *pvmw.pte;
+ err = 0;
+
+out_unlock:
+ page_vma_mapped_walk_done(&pvmw);
+out_mn:
+ mmu_notifier_invalidate_range_end(&range);
+out:
+ return err;
+}
+
+#define MERGE_ERR_PGERR 1 /* the page is invalid cannot continue */
+#define MERGE_ERR_COLLI 2 /* there is a collision */
+#define MERGE_ERR_COLLI_MAX 3 /* collision at the max hash strength */
+#define MERGE_ERR_CHANGED 4 /* the page has changed since last hash */
+
+
+/**
+ * replace_page - replace page in vma by new ksm page
+ * @vma: vma that holds the pte pointing to page
+ * @page: the page we are replacing by kpage
+ * @kpage: the ksm page we replace page by
+ * @orig_pte: the original value of the pte
+ *
+ * Returns 0 on success, MERGE_ERR_PGERR on failure.
+ */
+static int replace_page(struct vm_area_struct *vma, struct page *page,
+ struct page *kpage, pte_t orig_pte)
+{
+ struct mm_struct *mm = vma->vm_mm;
+ struct mmu_notifier_range range;
+ pgd_t *pgd;
+ p4d_t *p4d;
+ pud_t *pud;
+ pmd_t *pmd;
+ pte_t *ptep;
+ spinlock_t *ptl;
+ pte_t entry;
+
+ unsigned long addr;
+ int err = MERGE_ERR_PGERR;
+
+ addr = page_address_in_vma(page, vma);
+ if (addr == -EFAULT)
+ goto out;
+
+ pgd = pgd_offset(mm, addr);
+ if (!pgd_present(*pgd))
+ goto out;
+
+ p4d = p4d_offset(pgd, addr);
+ pud = pud_offset(p4d, addr);
+ if (!pud_present(*pud))
+ goto out;
+
+ pmd = pmd_offset(pud, addr);
+ BUG_ON(pmd_trans_huge(*pmd));
+ if (!pmd_present(*pmd))
+ goto out;
+
+ mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, mm, addr,
+ addr + PAGE_SIZE);
+ mmu_notifier_invalidate_range_start(&range);
+
+ ptep = pte_offset_map_lock(mm, pmd, addr, &ptl);
+ if (!pte_same(*ptep, orig_pte)) {
+ pte_unmap_unlock(ptep, ptl);
+ goto out_mn;
+ }
+
+ flush_cache_page(vma, addr, pte_pfn(*ptep));
+ ptep_clear_flush_notify(vma, addr, ptep);
+ entry = mk_pte(kpage, vma->vm_page_prot);
+
+ /* special treatment is needed for zero_page */
+ if ((page_to_pfn(kpage) == uksm_zero_pfn) ||
+ (page_to_pfn(kpage) == zero_pfn)) {
+ entry = pte_mkspecial(entry);
+ dec_mm_counter(mm, MM_ANONPAGES);
+ inc_zone_page_state(page, NR_UKSM_ZERO_PAGES);
+ } else {
+ get_page(kpage);
+ page_add_anon_rmap(kpage, vma, addr, false);
+ }
+
+ set_pte_at_notify(mm, addr, ptep, entry);
+
+ page_remove_rmap(page, false);
+ if (!page_mapped(page))
+ try_to_free_swap(page);
+ put_page(page);
+
+ pte_unmap_unlock(ptep, ptl);
+ err = 0;
+out_mn:
+ mmu_notifier_invalidate_range_end(&range);
+out:
+ return err;
+}
+
+
+/**
+ * Fully hash a page with HASH_STRENGTH_MAX return a non-zero hash value. The
+ * zero hash value at HASH_STRENGTH_MAX is used to indicated that its
+ * hash_max member has not been calculated.
+ *
+ * @page The page needs to be hashed
+ * @hash_old The hash value calculated with current hash strength
+ *
+ * return the new hash value calculated at HASH_STRENGTH_MAX
+ */
+static inline u32 page_hash_max(struct page *page, u32 hash_old)
+{
+ u32 hash_max = 0;
+ void *addr;
+
+ addr = kmap_atomic(page);
+ hash_max = delta_hash(addr, hash_strength,
+ HASH_STRENGTH_MAX, hash_old);
+
+ kunmap_atomic(addr);
+
+ if (!hash_max)
+ hash_max = 1;
+
+ inc_rshash_neg(HASH_STRENGTH_MAX - hash_strength);
+ return hash_max;
+}
+
+/*
+ * We compare the hash again, to ensure that it is really a hash collision
+ * instead of being caused by page write.
+ */
+static inline int check_collision(struct rmap_item *rmap_item,
+ u32 hash)
+{
+ int err;
+ struct page *page = rmap_item->page;
+
+ /* if this rmap_item has already been hash_maxed, then the collision
+ * must appears in the second-level rbtree search. In this case we check
+ * if its hash_max value has been changed. Otherwise, the collision
+ * happens in the first-level rbtree search, so we check against it's
+ * current hash value.
+ */
+ if (rmap_item->hash_max) {
+ inc_rshash_neg(memcmp_cost);
+ inc_rshash_neg(HASH_STRENGTH_MAX - hash_strength);
+
+ if (rmap_item->hash_max == page_hash_max(page, hash))
+ err = MERGE_ERR_COLLI;
+ else
+ err = MERGE_ERR_CHANGED;
+ } else {
+ inc_rshash_neg(memcmp_cost + hash_strength);
+
+ if (page_hash(page, hash_strength, 0) == hash)
+ err = MERGE_ERR_COLLI;
+ else
+ err = MERGE_ERR_CHANGED;
+ }
+
+ return err;
+}
+
+/**
+ * Try to merge a rmap_item.page with a kpage in stable node. kpage must
+ * already be a ksm page.
+ *
+ * @return 0 if the pages were merged, -EFAULT otherwise.
+ */
+static int try_to_merge_with_uksm_page(struct rmap_item *rmap_item,
+ struct page *kpage, u32 hash)
+{
+ struct vm_area_struct *vma = rmap_item->slot->vma;
+ struct mm_struct *mm = vma->vm_mm;
+ pte_t orig_pte = __pte(0);
+ int err = MERGE_ERR_PGERR;
+ struct page *page;
+
+ if (uksm_test_exit(mm))
+ goto out;
+
+ page = rmap_item->page;
+
+ if (page == kpage) { /* ksm page forked */
+ err = 0;
+ goto out;
+ }
+
+ /*
+ * We need the page lock to read a stable PageSwapCache in
+ * write_protect_page(). We use trylock_page() instead of
+ * lock_page() because we don't want to wait here - we
+ * prefer to continue scanning and merging different pages,
+ * then come back to this page when it is unlocked.
+ */
+ if (!trylock_page(page))
+ goto out;
+
+ if (!PageAnon(page) || !PageKsm(kpage))
+ goto out_unlock;
+
+ if (PageTransCompound(page)) {
+ err = split_huge_page(page);
+ if (err)
+ goto out_unlock;
+ }
+
+ /*
+ * If this anonymous page is mapped only here, its pte may need
+ * to be write-protected. If it's mapped elsewhere, all of its
+ * ptes are necessarily already write-protected. But in either
+ * case, we need to lock and check page_count is not raised.
+ */
+ if (write_protect_page(vma, page, &orig_pte, NULL) == 0) {
+ if (pages_identical_with_cost(page, kpage))
+ err = replace_page(vma, page, kpage, orig_pte);
+ else
+ err = check_collision(rmap_item, hash);
+ }
+
+ if ((vma->vm_flags & VM_LOCKED) && kpage && !err) {
+ munlock_vma_page(page);
+ if (!PageMlocked(kpage)) {
+ unlock_page(page);
+ lock_page(kpage);
+ mlock_vma_page(kpage);
+ page = kpage; /* for final unlock */
+ }
+ }
+
+out_unlock:
+ unlock_page(page);
+out:
+ return err;
+}
+
+
+
+/**
+ * If two pages fail to merge in try_to_merge_two_pages, then we have a chance
+ * to restore a page mapping that has been changed in try_to_merge_two_pages.
+ *
+ * @return 0 on success.
+ */
+static int restore_uksm_page_pte(struct vm_area_struct *vma, unsigned long addr,
+ pte_t orig_pte, pte_t wprt_pte)
+{
+ struct mm_struct *mm = vma->vm_mm;
+ pgd_t *pgd;
+ p4d_t *p4d;
+ pud_t *pud;
+ pmd_t *pmd;
+ pte_t *ptep;
+ spinlock_t *ptl;
+
+ int err = -EFAULT;
+
+ pgd = pgd_offset(mm, addr);
+ if (!pgd_present(*pgd))
+ goto out;
+
+ p4d = p4d_offset(pgd, addr);
+ pud = pud_offset(p4d, addr);
+ if (!pud_present(*pud))
+ goto out;
+
+ pmd = pmd_offset(pud, addr);
+ if (!pmd_present(*pmd))
+ goto out;
+
+ ptep = pte_offset_map_lock(mm, pmd, addr, &ptl);
+ if (!pte_same(*ptep, wprt_pte)) {
+ /* already copied, let it be */
+ pte_unmap_unlock(ptep, ptl);
+ goto out;
+ }
+
+ /*
+ * Good boy, still here. When we still get the ksm page, it does not
+ * return to the free page pool, there is no way that a pte was changed
+ * to other page and gets back to this page. And remind that ksm page
+ * do not reuse in do_wp_page(). So it's safe to restore the original
+ * pte.
+ */
+ flush_cache_page(vma, addr, pte_pfn(*ptep));
+ ptep_clear_flush_notify(vma, addr, ptep);
+ set_pte_at_notify(mm, addr, ptep, orig_pte);
+
+ pte_unmap_unlock(ptep, ptl);
+ err = 0;
+out:
+ return err;
+}
+
+/**
+ * try_to_merge_two_pages() - take two identical pages and prepare
+ * them to be merged into one page(rmap_item->page)
+ *
+ * @return 0 if we successfully merged two identical pages into
+ * one ksm page. MERGE_ERR_COLLI if it's only a hash collision
+ * search in rbtree. MERGE_ERR_CHANGED if rmap_item has been
+ * changed since it's hashed. MERGE_ERR_PGERR otherwise.
+ *
+ */
+static int try_to_merge_two_pages(struct rmap_item *rmap_item,
+ struct rmap_item *tree_rmap_item,
+ u32 hash)
+{
+ pte_t orig_pte1 = __pte(0), orig_pte2 = __pte(0);
+ pte_t wprt_pte1 = __pte(0), wprt_pte2 = __pte(0);
+ struct vm_area_struct *vma1 = rmap_item->slot->vma;
+ struct vm_area_struct *vma2 = tree_rmap_item->slot->vma;
+ struct page *page = rmap_item->page;
+ struct page *tree_page = tree_rmap_item->page;
+ int err = MERGE_ERR_PGERR;
+ struct address_space *saved_mapping;
+
+
+ if (rmap_item->page == tree_rmap_item->page)
+ goto out;
+
+ if (!trylock_page(page))
+ goto out;
+
+ if (!PageAnon(page))
+ goto out_unlock;
+
+ if (PageTransCompound(page)) {
+ err = split_huge_page(page);
+ if (err)
+ goto out_unlock;
+ }
+
+ if (write_protect_page(vma1, page, &wprt_pte1, &orig_pte1) != 0) {
+ unlock_page(page);
+ goto out;
+ }
+
+ /*
+ * While we hold page lock, upgrade page from
+ * PageAnon+anon_vma to PageKsm+NULL stable_node:
+ * stable_tree_insert() will update stable_node.
+ */
+ saved_mapping = page->mapping;
+ set_page_stable_node(page, NULL);
+ mark_page_accessed(page);
+ if (!PageDirty(page))
+ SetPageDirty(page);
+
+ unlock_page(page);
+
+ if (!trylock_page(tree_page))
+ goto restore_out;
+
+ if (!PageAnon(tree_page)) {
+ unlock_page(tree_page);
+ goto restore_out;
+ }
+
+ if (PageTransCompound(tree_page)) {
+ err = split_huge_page(tree_page);
+ if (err) {
+ unlock_page(tree_page);
+ goto restore_out;
+ }
+ }
+
+ if (write_protect_page(vma2, tree_page, &wprt_pte2, &orig_pte2) != 0) {
+ unlock_page(tree_page);
+ goto restore_out;
+ }
+
+ if (pages_identical_with_cost(page, tree_page)) {
+ err = replace_page(vma2, tree_page, page, wprt_pte2);
+ if (err) {
+ unlock_page(tree_page);
+ goto restore_out;
+ }
+
+ if ((vma2->vm_flags & VM_LOCKED)) {
+ munlock_vma_page(tree_page);
+ if (!PageMlocked(page)) {
+ unlock_page(tree_page);
+ lock_page(page);
+ mlock_vma_page(page);
+ tree_page = page; /* for final unlock */
+ }
+ }
+
+ unlock_page(tree_page);
+
+ goto out; /* success */
+
+ } else {
+ if (tree_rmap_item->hash_max &&
+ tree_rmap_item->hash_max == rmap_item->hash_max) {
+ err = MERGE_ERR_COLLI_MAX;
+ } else if (page_hash(page, hash_strength, 0) ==
+ page_hash(tree_page, hash_strength, 0)) {
+ inc_rshash_neg(memcmp_cost + hash_strength * 2);
+ err = MERGE_ERR_COLLI;
+ } else {
+ err = MERGE_ERR_CHANGED;
+ }
+
+ unlock_page(tree_page);
+ }
+
+restore_out:
+ lock_page(page);
+ if (!restore_uksm_page_pte(vma1, get_rmap_addr(rmap_item),
+ orig_pte1, wprt_pte1))
+ page->mapping = saved_mapping;
+
+out_unlock:
+ unlock_page(page);
+out:
+ return err;
+}
+
+static inline int hash_cmp(u32 new_val, u32 node_val)
+{
+ if (new_val > node_val)
+ return 1;
+ else if (new_val < node_val)
+ return -1;
+ else
+ return 0;
+}
+
+static inline u32 rmap_item_hash_max(struct rmap_item *item, u32 hash)
+{
+ u32 hash_max = item->hash_max;
+
+ if (!hash_max) {
+ hash_max = page_hash_max(item->page, hash);
+
+ item->hash_max = hash_max;
+ }
+
+ return hash_max;
+}
+
+
+
+/**
+ * stable_tree_search() - search the stable tree for a page
+ *
+ * @item: the rmap_item we are comparing with
+ * @hash: the hash value of this item->page already calculated
+ *
+ * @return the page we have found, NULL otherwise. The page returned has
+ * been gotten.
+ */
+static struct page *stable_tree_search(struct rmap_item *item, u32 hash)
+{
+ struct rb_node *node = root_stable_treep->rb_node;
+ struct tree_node *tree_node;
+ unsigned long hash_max;
+ struct page *page = item->page;
+ struct stable_node *stable_node;
+
+ stable_node = page_stable_node(page);
+ if (stable_node) {
+ /* ksm page forked, that is
+ * if (PageKsm(page) && !in_stable_tree(rmap_item))
+ * it's actually gotten once outside.
+ */
+ get_page(page);
+ return page;
+ }
+
+ while (node) {
+ int cmp;
+
+ tree_node = rb_entry(node, struct tree_node, node);
+
+ cmp = hash_cmp(hash, tree_node->hash);
+
+ if (cmp < 0)
+ node = node->rb_left;
+ else if (cmp > 0)
+ node = node->rb_right;
+ else
+ break;
+ }
+
+ if (!node)
+ return NULL;
+
+ if (tree_node->count == 1) {
+ stable_node = rb_entry(tree_node->sub_root.rb_node,
+ struct stable_node, node);
+ BUG_ON(!stable_node);
+
+ goto get_page_out;
+ }
+
+ /*
+ * ok, we have to search the second
+ * level subtree, hash the page to a
+ * full strength.
+ */
+ node = tree_node->sub_root.rb_node;
+ BUG_ON(!node);
+ hash_max = rmap_item_hash_max(item, hash);
+
+ while (node) {
+ int cmp;
+
+ stable_node = rb_entry(node, struct stable_node, node);
+
+ cmp = hash_cmp(hash_max, stable_node->hash_max);
+
+ if (cmp < 0)
+ node = node->rb_left;
+ else if (cmp > 0)
+ node = node->rb_right;
+ else
+ goto get_page_out;
+ }
+
+ return NULL;
+
+get_page_out:
+ page = get_uksm_page(stable_node, 1, 1);
+ return page;
+}
+
+static int try_merge_rmap_item(struct rmap_item *item,
+ struct page *kpage,
+ struct page *tree_page)
+{
+ struct vm_area_struct *vma = item->slot->vma;
+ struct page_vma_mapped_walk pvmw = {
+ .page = kpage,
+ .vma = vma,
+ };
+
+ pvmw.address = get_rmap_addr(item);
+ if (!page_vma_mapped_walk(&pvmw))
+ return 0;
+
+ if (pte_write(*pvmw.pte)) {
+ /* has changed, abort! */
+ page_vma_mapped_walk_done(&pvmw);
+ return 0;
+ }
+
+ get_page(tree_page);
+ page_add_anon_rmap(tree_page, vma, pvmw.address, false);
+
+ flush_cache_page(vma, pvmw.address, page_to_pfn(kpage));
+ ptep_clear_flush_notify(vma, pvmw.address, pvmw.pte);
+ set_pte_at_notify(vma->vm_mm, pvmw.address, pvmw.pte,
+ mk_pte(tree_page, vma->vm_page_prot));
+
+ page_remove_rmap(kpage, false);
+ put_page(kpage);
+
+ page_vma_mapped_walk_done(&pvmw);
+
+ return 1;
+}
+
+/**
+ * try_to_merge_with_stable_page() - when two rmap_items need to be inserted
+ * into stable tree, the page was found to be identical to a stable ksm page,
+ * this is the last chance we can merge them into one.
+ *
+ * @item1: the rmap_item holding the page which we wanted to insert
+ * into stable tree.
+ * @item2: the other rmap_item we found when unstable tree search
+ * @oldpage: the page currently mapped by the two rmap_items
+ * @tree_page: the page we found identical in stable tree node
+ * @success1: return if item1 is successfully merged
+ * @success2: return if item2 is successfully merged
+ */
+static void try_merge_with_stable(struct rmap_item *item1,
+ struct rmap_item *item2,
+ struct page **kpage,
+ struct page *tree_page,
+ int *success1, int *success2)
+{
+ struct vm_area_struct *vma1 = item1->slot->vma;
+ struct vm_area_struct *vma2 = item2->slot->vma;
+ *success1 = 0;
+ *success2 = 0;
+
+ if (unlikely(*kpage == tree_page)) {
+ /* I don't think this can really happen */
+ pr_warn("UKSM: unexpected condition detected in "
+ "%s -- *kpage == tree_page !\n", __func__);
+ *success1 = 1;
+ *success2 = 1;
+ return;
+ }
+
+ if (!PageAnon(*kpage) || !PageKsm(*kpage))
+ goto failed;
+
+ if (!trylock_page(tree_page))
+ goto failed;
+
+ /* If the oldpage is still ksm and still pointed
+ * to in the right place, and still write protected,
+ * we are confident it's not changed, no need to
+ * memcmp anymore.
+ * be ware, we cannot take nested pte locks,
+ * deadlock risk.
+ */
+ if (!try_merge_rmap_item(item1, *kpage, tree_page))
+ goto unlock_failed;
+
+ /* ok, then vma2, remind that pte1 already set */
+ if (!try_merge_rmap_item(item2, *kpage, tree_page))
+ goto success_1;
+
+ *success2 = 1;
+success_1:
+ *success1 = 1;
+
+
+ if ((*success1 && vma1->vm_flags & VM_LOCKED) ||
+ (*success2 && vma2->vm_flags & VM_LOCKED)) {
+ munlock_vma_page(*kpage);
+ if (!PageMlocked(tree_page))
+ mlock_vma_page(tree_page);
+ }
+
+ /*
+ * We do not need oldpage any more in the caller, so can break the lock
+ * now.
+ */
+ unlock_page(*kpage);
+ *kpage = tree_page; /* Get unlocked outside. */
+ return;
+
+unlock_failed:
+ unlock_page(tree_page);
+failed:
+ return;
+}
+
+static inline void stable_node_hash_max(struct stable_node *node,
+ struct page *page, u32 hash)
+{
+ u32 hash_max = node->hash_max;
+
+ if (!hash_max) {
+ hash_max = page_hash_max(page, hash);
+ node->hash_max = hash_max;
+ }
+}
+
+static inline
+struct stable_node *new_stable_node(struct tree_node *tree_node,
+ struct page *kpage, u32 hash_max)
+{
+ struct stable_node *new_stable_node;
+
+ new_stable_node = alloc_stable_node();
+ if (!new_stable_node)
+ return NULL;
+
+ new_stable_node->kpfn = page_to_pfn(kpage);
+ new_stable_node->hash_max = hash_max;
+ new_stable_node->tree_node = tree_node;
+ set_page_stable_node(kpage, new_stable_node);
+
+ return new_stable_node;
+}
+
+static inline
+struct stable_node *first_level_insert(struct tree_node *tree_node,
+ struct rmap_item *rmap_item,
+ struct rmap_item *tree_rmap_item,
+ struct page **kpage, u32 hash,
+ int *success1, int *success2)
+{
+ int cmp;
+ struct page *tree_page;
+ u32 hash_max = 0;
+ struct stable_node *stable_node, *new_snode;
+ struct rb_node *parent = NULL, **new;
+
+ /* this tree node contains no sub-tree yet */
+ stable_node = rb_entry(tree_node->sub_root.rb_node,
+ struct stable_node, node);
+
+ tree_page = get_uksm_page(stable_node, 1, 0);
+ if (tree_page) {
+ cmp = memcmp_pages_with_cost(*kpage, tree_page, 1);
+ if (!cmp) {
+ try_merge_with_stable(rmap_item, tree_rmap_item, kpage,
+ tree_page, success1, success2);
+ put_page(tree_page);
+ if (!*success1 && !*success2)
+ goto failed;
+
+ return stable_node;
+
+ } else {
+ /*
+ * collision in first level try to create a subtree.
+ * A new node need to be created.
+ */
+ put_page(tree_page);
+
+ stable_node_hash_max(stable_node, tree_page,
+ tree_node->hash);
+ hash_max = rmap_item_hash_max(rmap_item, hash);
+ cmp = hash_cmp(hash_max, stable_node->hash_max);
+
+ parent = &stable_node->node;
+ if (cmp < 0)
+ new = &parent->rb_left;
+ else if (cmp > 0)
+ new = &parent->rb_right;
+ else
+ goto failed;
+ }
+
+ } else {
+ /* the only stable_node deleted, we reuse its tree_node.
+ */
+ parent = NULL;
+ new = &tree_node->sub_root.rb_node;
+ }
+
+ new_snode = new_stable_node(tree_node, *kpage, hash_max);
+ if (!new_snode)
+ goto failed;
+
+ rb_link_node(&new_snode->node, parent, new);
+ rb_insert_color(&new_snode->node, &tree_node->sub_root);
+ tree_node->count++;
+ *success1 = *success2 = 1;
+
+ return new_snode;
+
+failed:
+ return NULL;
+}
+
+static inline
+struct stable_node *stable_subtree_insert(struct tree_node *tree_node,
+ struct rmap_item *rmap_item,
+ struct rmap_item *tree_rmap_item,
+ struct page **kpage, u32 hash,
+ int *success1, int *success2)
+{
+ struct page *tree_page;
+ u32 hash_max;
+ struct stable_node *stable_node, *new_snode;
+ struct rb_node *parent, **new;
+
+research:
+ parent = NULL;
+ new = &tree_node->sub_root.rb_node;
+ BUG_ON(!*new);
+ hash_max = rmap_item_hash_max(rmap_item, hash);
+ while (*new) {
+ int cmp;
+
+ stable_node = rb_entry(*new, struct stable_node, node);
+
+ cmp = hash_cmp(hash_max, stable_node->hash_max);
+
+ if (cmp < 0) {
+ parent = *new;
+ new = &parent->rb_left;
+ } else if (cmp > 0) {
+ parent = *new;
+ new = &parent->rb_right;
+ } else {
+ tree_page = get_uksm_page(stable_node, 1, 0);
+ if (tree_page) {
+ cmp = memcmp_pages_with_cost(*kpage, tree_page, 1);
+ if (!cmp) {
+ try_merge_with_stable(rmap_item,
+ tree_rmap_item, kpage,
+ tree_page, success1, success2);
+
+ put_page(tree_page);
+ if (!*success1 && !*success2)
+ goto failed;
+ /*
+ * successfully merged with a stable
+ * node
+ */
+ return stable_node;
+ } else {
+ put_page(tree_page);
+ goto failed;
+ }
+ } else {
+ /*
+ * stable node may be deleted,
+ * and subtree maybe
+ * restructed, cannot
+ * continue, research it.
+ */
+ if (tree_node->count) {
+ goto research;
+ } else {
+ /* reuse the tree node*/
+ parent = NULL;
+ new = &tree_node->sub_root.rb_node;
+ }
+ }
+ }
+ }
+
+ new_snode = new_stable_node(tree_node, *kpage, hash_max);
+ if (!new_snode)
+ goto failed;
+
+ rb_link_node(&new_snode->node, parent, new);
+ rb_insert_color(&new_snode->node, &tree_node->sub_root);
+ tree_node->count++;
+ *success1 = *success2 = 1;
+
+ return new_snode;
+
+failed:
+ return NULL;
+}
+
+
+/**
+ * stable_tree_insert() - try to insert a merged page in unstable tree to
+ * the stable tree
+ *
+ * @kpage: the page need to be inserted
+ * @hash: the current hash of this page
+ * @rmap_item: the rmap_item being scanned
+ * @tree_rmap_item: the rmap_item found on unstable tree
+ * @success1: return if rmap_item is merged
+ * @success2: return if tree_rmap_item is merged
+ *
+ * @return the stable_node on stable tree if at least one
+ * rmap_item is inserted into stable tree, NULL
+ * otherwise.
+ */
+static struct stable_node *
+stable_tree_insert(struct page **kpage, u32 hash,
+ struct rmap_item *rmap_item,
+ struct rmap_item *tree_rmap_item,
+ int *success1, int *success2)
+{
+ struct rb_node **new = &root_stable_treep->rb_node;
+ struct rb_node *parent = NULL;
+ struct stable_node *stable_node;
+ struct tree_node *tree_node;
+ u32 hash_max = 0;
+
+ *success1 = *success2 = 0;
+
+ while (*new) {
+ int cmp;
+
+ tree_node = rb_entry(*new, struct tree_node, node);
+
+ cmp = hash_cmp(hash, tree_node->hash);
+
+ if (cmp < 0) {
+ parent = *new;
+ new = &parent->rb_left;
+ } else if (cmp > 0) {
+ parent = *new;
+ new = &parent->rb_right;
+ } else
+ break;
+ }
+
+ if (*new) {
+ if (tree_node->count == 1) {
+ stable_node = first_level_insert(tree_node, rmap_item,
+ tree_rmap_item, kpage,
+ hash, success1, success2);
+ } else {
+ stable_node = stable_subtree_insert(tree_node,
+ rmap_item, tree_rmap_item, kpage,
+ hash, success1, success2);
+ }
+ } else {
+
+ /* no tree node found */
+ tree_node = alloc_tree_node(stable_tree_node_listp);
+ if (!tree_node) {
+ stable_node = NULL;
+ goto out;
+ }
+
+ stable_node = new_stable_node(tree_node, *kpage, hash_max);
+ if (!stable_node) {
+ free_tree_node(tree_node);
+ goto out;
+ }
+
+ tree_node->hash = hash;
+ rb_link_node(&tree_node->node, parent, new);
+ rb_insert_color(&tree_node->node, root_stable_treep);
+ parent = NULL;
+ new = &tree_node->sub_root.rb_node;
+
+ rb_link_node(&stable_node->node, parent, new);
+ rb_insert_color(&stable_node->node, &tree_node->sub_root);
+ tree_node->count++;
+ *success1 = *success2 = 1;
+ }
+
+out:
+ return stable_node;
+}
+
+
+/**
+ * get_tree_rmap_item_page() - try to get the page and lock the mmap_sem
+ *
+ * @return 0 on success, -EBUSY if unable to lock the mmap_sem,
+ * -EINVAL if the page mapping has been changed.
+ */
+static inline int get_tree_rmap_item_page(struct rmap_item *tree_rmap_item)
+{
+ int err;
+
+ err = get_mergeable_page_lock_mmap(tree_rmap_item);
+
+ if (err == -EINVAL) {
+ /* its page map has been changed, remove it */
+ remove_rmap_item_from_tree(tree_rmap_item);
+ }
+
+ /* The page is gotten and mmap_sem is locked now. */
+ return err;
+}
+
+
+/**
+ * unstable_tree_search_insert() - search an unstable tree rmap_item with the
+ * same hash value. Get its page and trylock the mmap_sem
+ */
+static inline
+struct rmap_item *unstable_tree_search_insert(struct rmap_item *rmap_item,
+ u32 hash)
+
+{
+ struct rb_node **new = &root_unstable_tree.rb_node;
+ struct rb_node *parent = NULL;
+ struct tree_node *tree_node;
+ u32 hash_max;
+ struct rmap_item *tree_rmap_item;
+
+ while (*new) {
+ int cmp;
+
+ tree_node = rb_entry(*new, struct tree_node, node);
+
+ cmp = hash_cmp(hash, tree_node->hash);
+
+ if (cmp < 0) {
+ parent = *new;
+ new = &parent->rb_left;
+ } else if (cmp > 0) {
+ parent = *new;
+ new = &parent->rb_right;
+ } else
+ break;
+ }
+
+ if (*new) {
+ /* got the tree_node */
+ if (tree_node->count == 1) {
+ tree_rmap_item = rb_entry(tree_node->sub_root.rb_node,
+ struct rmap_item, node);
+ BUG_ON(!tree_rmap_item);
+
+ goto get_page_out;
+ }
+
+ /* well, search the collision subtree */
+ new = &tree_node->sub_root.rb_node;
+ BUG_ON(!*new);
+ hash_max = rmap_item_hash_max(rmap_item, hash);
+
+ while (*new) {
+ int cmp;
+
+ tree_rmap_item = rb_entry(*new, struct rmap_item,
+ node);
+
+ cmp = hash_cmp(hash_max, tree_rmap_item->hash_max);
+ parent = *new;
+ if (cmp < 0)
+ new = &parent->rb_left;
+ else if (cmp > 0)
+ new = &parent->rb_right;
+ else
+ goto get_page_out;
+ }
+ } else {
+ /* alloc a new tree_node */
+ tree_node = alloc_tree_node(&unstable_tree_node_list);
+ if (!tree_node)
+ return NULL;
+
+ tree_node->hash = hash;
+ rb_link_node(&tree_node->node, parent, new);
+ rb_insert_color(&tree_node->node, &root_unstable_tree);
+ parent = NULL;
+ new = &tree_node->sub_root.rb_node;
+ }
+
+ /* did not found even in sub-tree */
+ rmap_item->tree_node = tree_node;
+ rmap_item->address |= UNSTABLE_FLAG;
+ rmap_item->hash_round = uksm_hash_round;
+ rb_link_node(&rmap_item->node, parent, new);
+ rb_insert_color(&rmap_item->node, &tree_node->sub_root);
+
+ uksm_pages_unshared++;
+ return NULL;
+
+get_page_out:
+ if (tree_rmap_item->page == rmap_item->page)
+ return NULL;
+
+ if (get_tree_rmap_item_page(tree_rmap_item))
+ return NULL;
+
+ return tree_rmap_item;
+}
+
+static void hold_anon_vma(struct rmap_item *rmap_item,
+ struct anon_vma *anon_vma)
+{
+ rmap_item->anon_vma = anon_vma;
+ get_anon_vma(anon_vma);
+}
+
+
+/**
+ * stable_tree_append() - append a rmap_item to a stable node. Deduplication
+ * ratio statistics is done in this function.
+ *
+ */
+static void stable_tree_append(struct rmap_item *rmap_item,
+ struct stable_node *stable_node, int logdedup)
+{
+ struct node_vma *node_vma = NULL, *new_node_vma, *node_vma_cont = NULL;
+ unsigned long key = (unsigned long)rmap_item->slot;
+ unsigned long factor = rmap_item->slot->rung->step;
+
+ BUG_ON(!stable_node);
+ rmap_item->address |= STABLE_FLAG;
+
+ if (hlist_empty(&stable_node->hlist)) {
+ uksm_pages_shared++;
+ goto node_vma_new;
+ } else {
+ uksm_pages_sharing++;
+ }
+
+ hlist_for_each_entry(node_vma, &stable_node->hlist, hlist) {
+ if (node_vma->key >= key)
+ break;
+
+ if (logdedup) {
+ node_vma->slot->pages_bemerged += factor;
+ if (list_empty(&node_vma->slot->dedup_list))
+ list_add(&node_vma->slot->dedup_list,
+ &vma_slot_dedup);
+ }
+ }
+
+ if (node_vma) {
+ if (node_vma->key == key) {
+ node_vma_cont = hlist_entry_safe(node_vma->hlist.next, struct node_vma, hlist);
+ goto node_vma_ok;
+ } else if (node_vma->key > key) {
+ node_vma_cont = node_vma;
+ }
+ }
+
+node_vma_new:
+ /* no same vma already in node, alloc a new node_vma */
+ new_node_vma = alloc_node_vma();
+ BUG_ON(!new_node_vma);
+ new_node_vma->head = stable_node;
+ new_node_vma->slot = rmap_item->slot;
+
+ if (!node_vma) {
+ hlist_add_head(&new_node_vma->hlist, &stable_node->hlist);
+ } else if (node_vma->key != key) {
+ if (node_vma->key < key)
+ hlist_add_behind(&new_node_vma->hlist, &node_vma->hlist);
+ else {
+ hlist_add_before(&new_node_vma->hlist,
+ &node_vma->hlist);
+ }
+
+ }
+ node_vma = new_node_vma;
+
+node_vma_ok: /* ok, ready to add to the list */
+ rmap_item->head = node_vma;
+ hlist_add_head(&rmap_item->hlist, &node_vma->rmap_hlist);
+ hold_anon_vma(rmap_item, rmap_item->slot->vma->anon_vma);
+ if (logdedup) {
+ rmap_item->slot->pages_merged++;
+ if (node_vma_cont) {
+ node_vma = node_vma_cont;
+ hlist_for_each_entry_continue(node_vma, hlist) {
+ node_vma->slot->pages_bemerged += factor;
+ if (list_empty(&node_vma->slot->dedup_list))
+ list_add(&node_vma->slot->dedup_list,
+ &vma_slot_dedup);
+ }
+ }
+ }
+}
+
+/*
+ * We use break_ksm to break COW on a ksm page: it's a stripped down
+ *
+ * if (get_user_pages(addr, 1, 1, 1, &page, NULL) == 1)
+ * put_page(page);
+ *
+ * but taking great care only to touch a ksm page, in a VM_MERGEABLE vma,
+ * in case the application has unmapped and remapped mm,addr meanwhile.
+ * Could a ksm page appear anywhere else? Actually yes, in a VM_PFNMAP
+ * mmap of /dev/mem or /dev/kmem, where we would not want to touch it.
+ */
+static int break_ksm(struct vm_area_struct *vma, unsigned long addr)
+{
+ struct page *page;
+ int ret = 0;
+
+ do {
+ cond_resched();
+ page = follow_page(vma, addr, FOLL_GET | FOLL_MIGRATION | FOLL_REMOTE);
+ if (IS_ERR_OR_NULL(page))
+ break;
+ if (PageKsm(page)) {
+ ret = handle_mm_fault(vma, addr,
+ FAULT_FLAG_WRITE | FAULT_FLAG_REMOTE,
+ NULL);
+ } else
+ ret = VM_FAULT_WRITE;
+ put_page(page);
+ } while (!(ret & (VM_FAULT_WRITE | VM_FAULT_SIGBUS | VM_FAULT_SIGSEGV | VM_FAULT_OOM)));
+ /*
+ * We must loop because handle_mm_fault() may back out if there's
+ * any difficulty e.g. if pte accessed bit gets updated concurrently.
+ *
+ * VM_FAULT_WRITE is what we have been hoping for: it indicates that
+ * COW has been broken, even if the vma does not permit VM_WRITE;
+ * but note that a concurrent fault might break PageKsm for us.
+ *
+ * VM_FAULT_SIGBUS could occur if we race with truncation of the
+ * backing file, which also invalidates anonymous pages: that's
+ * okay, that truncation will have unmapped the PageKsm for us.
+ *
+ * VM_FAULT_OOM: at the time of writing (late July 2009), setting
+ * aside mem_cgroup limits, VM_FAULT_OOM would only be set if the
+ * current task has TIF_MEMDIE set, and will be OOM killed on return
+ * to user; and ksmd, having no mm, would never be chosen for that.
+ *
+ * But if the mm is in a limited mem_cgroup, then the fault may fail
+ * with VM_FAULT_OOM even if the current task is not TIF_MEMDIE; and
+ * even ksmd can fail in this way - though it's usually breaking ksm
+ * just to undo a merge it made a moment before, so unlikely to oom.
+ *
+ * That's a pity: we might therefore have more kernel pages allocated
+ * than we're counting as nodes in the stable tree; but uksm_do_scan
+ * will retry to break_cow on each pass, so should recover the page
+ * in due course. The important thing is to not let VM_MERGEABLE
+ * be cleared while any such pages might remain in the area.
+ */
+ return (ret & VM_FAULT_OOM) ? -ENOMEM : 0;
+}
+
+static void break_cow(struct rmap_item *rmap_item)
+{
+ struct vm_area_struct *vma = rmap_item->slot->vma;
+ struct mm_struct *mm = vma->vm_mm;
+ unsigned long addr = get_rmap_addr(rmap_item);
+
+ if (uksm_test_exit(mm))
+ goto out;
+
+ break_ksm(vma, addr);
+out:
+ return;
+}
+
+/*
+ * Though it's very tempting to unmerge in_stable_tree(rmap_item)s rather
+ * than check every pte of a given vma, the locking doesn't quite work for
+ * that - an rmap_item is assigned to the stable tree after inserting ksm
+ * page and upping mmap_sem. Nor does it fit with the way we skip dup'ing
+ * rmap_items from parent to child at fork time (so as not to waste time
+ * if exit comes before the next scan reaches it).
+ *
+ * Similarly, although we'd like to remove rmap_items (so updating counts
+ * and freeing memory) when unmerging an area, it's easier to leave that
+ * to the next pass of ksmd - consider, for example, how ksmd might be
+ * in cmp_and_merge_page on one of the rmap_items we would be removing.
+ */
+inline int unmerge_uksm_pages(struct vm_area_struct *vma,
+ unsigned long start, unsigned long end)
+{
+ unsigned long addr;
+ int err = 0;
+
+ for (addr = start; addr < end && !err; addr += PAGE_SIZE) {
+ if (uksm_test_exit(vma->vm_mm))
+ break;
+ if (signal_pending(current))
+ err = -ERESTARTSYS;
+ else
+ err = break_ksm(vma, addr);
+ }
+ return err;
+}
+
+static inline void inc_uksm_pages_scanned(void)
+{
+ u64 delta;
+
+
+ if (uksm_pages_scanned == U64_MAX) {
+ encode_benefit();
+
+ delta = uksm_pages_scanned >> pages_scanned_base;
+
+ if (CAN_OVERFLOW_U64(pages_scanned_stored, delta)) {
+ pages_scanned_stored >>= 1;
+ delta >>= 1;
+ pages_scanned_base++;
+ }
+
+ pages_scanned_stored += delta;
+
+ uksm_pages_scanned = uksm_pages_scanned_last = 0;
+ }
+
+ uksm_pages_scanned++;
+}
+
+static inline int find_zero_page_hash(int strength, u32 hash)
+{
+ return (zero_hash_table[strength] == hash);
+}
+
+static
+int cmp_and_merge_zero_page(struct vm_area_struct *vma, struct page *page)
+{
+ struct page *zero_page = empty_uksm_zero_page;
+ struct mm_struct *mm = vma->vm_mm;
+ pte_t orig_pte = __pte(0);
+ int err = -EFAULT;
+
+ if (uksm_test_exit(mm))
+ goto out;
+
+ if (!trylock_page(page))
+ goto out;
+
+ if (!PageAnon(page))
+ goto out_unlock;
+
+ if (PageTransCompound(page)) {
+ err = split_huge_page(page);
+ if (err)
+ goto out_unlock;
+ }
+
+ if (write_protect_page(vma, page, &orig_pte, 0) == 0) {
+ if (is_page_full_zero(page))
+ err = replace_page(vma, page, zero_page, orig_pte);
+ }
+
+out_unlock:
+ unlock_page(page);
+out:
+ return err;
+}
+
+/*
+ * cmp_and_merge_page() - first see if page can be merged into the stable
+ * tree; if not, compare hash to previous and if it's the same, see if page
+ * can be inserted into the unstable tree, or merged with a page already there
+ * and both transferred to the stable tree.
+ *
+ * @page: the page that we are searching identical page to.
+ * @rmap_item: the reverse mapping into the virtual address of this page
+ */
+static void cmp_and_merge_page(struct rmap_item *rmap_item, u32 hash)
+{
+ struct rmap_item *tree_rmap_item;
+ struct page *page;
+ struct page *kpage = NULL;
+ u32 hash_max;
+ int err;
+ unsigned int success1, success2;
+ struct stable_node *snode;
+ int cmp;
+ struct rb_node *parent = NULL, **new;
+
+ remove_rmap_item_from_tree(rmap_item);
+ page = rmap_item->page;
+
+ /* We first start with searching the page inside the stable tree */
+ kpage = stable_tree_search(rmap_item, hash);
+ if (kpage) {
+ err = try_to_merge_with_uksm_page(rmap_item, kpage,
+ hash);
+ if (!err) {
+ /*
+ * The page was successfully merged, add
+ * its rmap_item to the stable tree.
+ * page lock is needed because it's
+ * racing with try_to_unmap_ksm(), etc.
+ */
+ lock_page(kpage);
+ snode = page_stable_node(kpage);
+ stable_tree_append(rmap_item, snode, 1);
+ unlock_page(kpage);
+ put_page(kpage);
+ return; /* success */
+ }
+ put_page(kpage);
+
+ /*
+ * if it's a collision and it has been search in sub-rbtree
+ * (hash_max != 0), we want to abort, because if it is
+ * successfully merged in unstable tree, the collision trends to
+ * happen again.
+ */
+ if (err == MERGE_ERR_COLLI && rmap_item->hash_max)
+ return;
+ }
+
+ tree_rmap_item =
+ unstable_tree_search_insert(rmap_item, hash);
+ if (tree_rmap_item) {
+ err = try_to_merge_two_pages(rmap_item, tree_rmap_item, hash);
+ /*
+ * As soon as we merge this page, we want to remove the
+ * rmap_item of the page we have merged with from the unstable
+ * tree, and insert it instead as new node in the stable tree.
+ */
+ if (!err) {
+ kpage = page;
+ remove_rmap_item_from_tree(tree_rmap_item);
+ lock_page(kpage);
+ snode = stable_tree_insert(&kpage, hash,
+ rmap_item, tree_rmap_item,
+ &success1, &success2);
+
+ /*
+ * Do not log dedup for tree item, it's not counted as
+ * scanned in this round.
+ */
+ if (success2)
+ stable_tree_append(tree_rmap_item, snode, 0);
+
+ /*
+ * The order of these two stable append is important:
+ * we are scanning rmap_item.
+ */
+ if (success1)
+ stable_tree_append(rmap_item, snode, 1);
+
+ /*
+ * The original kpage may be unlocked inside
+ * stable_tree_insert() already. This page
+ * should be unlocked before doing
+ * break_cow().
+ */
+ unlock_page(kpage);
+
+ if (!success1)
+ break_cow(rmap_item);
+
+ if (!success2)
+ break_cow(tree_rmap_item);
+
+ } else if (err == MERGE_ERR_COLLI) {
+ BUG_ON(tree_rmap_item->tree_node->count > 1);
+
+ rmap_item_hash_max(tree_rmap_item,
+ tree_rmap_item->tree_node->hash);
+
+ hash_max = rmap_item_hash_max(rmap_item, hash);
+ cmp = hash_cmp(hash_max, tree_rmap_item->hash_max);
+ parent = &tree_rmap_item->node;
+ if (cmp < 0)
+ new = &parent->rb_left;
+ else if (cmp > 0)
+ new = &parent->rb_right;
+ else
+ goto put_up_out;
+
+ rmap_item->tree_node = tree_rmap_item->tree_node;
+ rmap_item->address |= UNSTABLE_FLAG;
+ rmap_item->hash_round = uksm_hash_round;
+ rb_link_node(&rmap_item->node, parent, new);
+ rb_insert_color(&rmap_item->node,
+ &tree_rmap_item->tree_node->sub_root);
+ rmap_item->tree_node->count++;
+ } else {
+ /*
+ * either one of the page has changed or they collide
+ * at the max hash, we consider them as ill items.
+ */
+ remove_rmap_item_from_tree(tree_rmap_item);
+ }
+put_up_out:
+ put_page(tree_rmap_item->page);
+ mmap_read_unlock(tree_rmap_item->slot->vma->vm_mm);
+ }
+}
+
+
+
+
+static inline unsigned long get_pool_index(struct vma_slot *slot,
+ unsigned long index)
+{
+ unsigned long pool_index;
+
+ pool_index = (sizeof(struct rmap_list_entry *) * index) >> PAGE_SHIFT;
+ if (pool_index >= slot->pool_size)
+ BUG();
+ return pool_index;
+}
+
+static inline unsigned long index_page_offset(unsigned long index)
+{
+ return offset_in_page(sizeof(struct rmap_list_entry *) * index);
+}
+
+static inline
+struct rmap_list_entry *get_rmap_list_entry(struct vma_slot *slot,
+ unsigned long index, int need_alloc)
+{
+ unsigned long pool_index;
+ struct page *page;
+ void *addr;
+
+
+ pool_index = get_pool_index(slot, index);
+ if (!slot->rmap_list_pool[pool_index]) {
+ if (!need_alloc)
+ return NULL;
+
+ page = alloc_page(GFP_KERNEL | __GFP_ZERO | __GFP_NOWARN);
+ if (!page)
+ return NULL;
+
+ slot->rmap_list_pool[pool_index] = page;
+ }
+
+ addr = kmap(slot->rmap_list_pool[pool_index]);
+ addr += index_page_offset(index);
+
+ return addr;
+}
+
+static inline void put_rmap_list_entry(struct vma_slot *slot,
+ unsigned long index)
+{
+ unsigned long pool_index;
+
+ pool_index = get_pool_index(slot, index);
+ BUG_ON(!slot->rmap_list_pool[pool_index]);
+ kunmap(slot->rmap_list_pool[pool_index]);
+}
+
+static inline int entry_is_new(struct rmap_list_entry *entry)
+{
+ return !entry->item;
+}
+
+static inline unsigned long get_index_orig_addr(struct vma_slot *slot,
+ unsigned long index)
+{
+ return slot->vma->vm_start + (index << PAGE_SHIFT);
+}
+
+static inline unsigned long get_entry_address(struct rmap_list_entry *entry)
+{
+ unsigned long addr;
+
+ if (is_addr(entry->addr))
+ addr = get_clean_addr(entry->addr);
+ else if (entry->item)
+ addr = get_rmap_addr(entry->item);
+ else
+ BUG();
+
+ return addr;
+}
+
+static inline struct rmap_item *get_entry_item(struct rmap_list_entry *entry)
+{
+ if (is_addr(entry->addr))
+ return NULL;
+
+ return entry->item;
+}
+
+static inline void inc_rmap_list_pool_count(struct vma_slot *slot,
+ unsigned long index)
+{
+ unsigned long pool_index;
+
+ pool_index = get_pool_index(slot, index);
+ BUG_ON(!slot->rmap_list_pool[pool_index]);
+ slot->pool_counts[pool_index]++;
+}
+
+static inline void dec_rmap_list_pool_count(struct vma_slot *slot,
+ unsigned long index)
+{
+ unsigned long pool_index;
+
+ pool_index = get_pool_index(slot, index);
+ BUG_ON(!slot->rmap_list_pool[pool_index]);
+ BUG_ON(!slot->pool_counts[pool_index]);
+ slot->pool_counts[pool_index]--;
+}
+
+static inline int entry_has_rmap(struct rmap_list_entry *entry)
+{
+ return !is_addr(entry->addr) && entry->item;
+}
+
+static inline void swap_entries(struct rmap_list_entry *entry1,
+ unsigned long index1,
+ struct rmap_list_entry *entry2,
+ unsigned long index2)
+{
+ struct rmap_list_entry tmp;
+
+ /* swapping two new entries is meaningless */
+ BUG_ON(entry_is_new(entry1) && entry_is_new(entry2));
+
+ tmp = *entry1;
+ *entry1 = *entry2;
+ *entry2 = tmp;
+
+ if (entry_has_rmap(entry1))
+ entry1->item->entry_index = index1;
+
+ if (entry_has_rmap(entry2))
+ entry2->item->entry_index = index2;
+
+ if (entry_has_rmap(entry1) && !entry_has_rmap(entry2)) {
+ inc_rmap_list_pool_count(entry1->item->slot, index1);
+ dec_rmap_list_pool_count(entry1->item->slot, index2);
+ } else if (!entry_has_rmap(entry1) && entry_has_rmap(entry2)) {
+ inc_rmap_list_pool_count(entry2->item->slot, index2);
+ dec_rmap_list_pool_count(entry2->item->slot, index1);
+ }
+}
+
+static inline void free_entry_item(struct rmap_list_entry *entry)
+{
+ unsigned long index;
+ struct rmap_item *item;
+
+ if (!is_addr(entry->addr)) {
+ BUG_ON(!entry->item);
+ item = entry->item;
+ entry->addr = get_rmap_addr(item);
+ set_is_addr(entry->addr);
+ index = item->entry_index;
+ remove_rmap_item_from_tree(item);
+ dec_rmap_list_pool_count(item->slot, index);
+ free_rmap_item(item);
+ }
+}
+
+static inline int pool_entry_boundary(unsigned long index)
+{
+ unsigned long linear_addr;
+
+ linear_addr = sizeof(struct rmap_list_entry *) * index;
+ return index && !offset_in_page(linear_addr);
+}
+
+static inline void try_free_last_pool(struct vma_slot *slot,
+ unsigned long index)
+{
+ unsigned long pool_index;
+
+ pool_index = get_pool_index(slot, index);
+ if (slot->rmap_list_pool[pool_index] &&
+ !slot->pool_counts[pool_index]) {
+ __free_page(slot->rmap_list_pool[pool_index]);
+ slot->rmap_list_pool[pool_index] = NULL;
+ slot->flags |= UKSM_SLOT_NEED_SORT;
+ }
+
+}
+
+static inline unsigned long vma_item_index(struct vm_area_struct *vma,
+ struct rmap_item *item)
+{
+ return (get_rmap_addr(item) - vma->vm_start) >> PAGE_SHIFT;
+}
+
+static int within_same_pool(struct vma_slot *slot,
+ unsigned long i, unsigned long j)
+{
+ unsigned long pool_i, pool_j;
+
+ pool_i = get_pool_index(slot, i);
+ pool_j = get_pool_index(slot, j);
+
+ return (pool_i == pool_j);
+}
+
+static void sort_rmap_entry_list(struct vma_slot *slot)
+{
+ unsigned long i, j;
+ struct rmap_list_entry *entry, *swap_entry;
+
+ entry = get_rmap_list_entry(slot, 0, 0);
+ for (i = 0; i < slot->pages; ) {
+
+ if (!entry)
+ goto skip_whole_pool;
+
+ if (entry_is_new(entry))
+ goto next_entry;
+
+ if (is_addr(entry->addr)) {
+ entry->addr = 0;
+ goto next_entry;
+ }
+
+ j = vma_item_index(slot->vma, entry->item);
+ if (j == i)
+ goto next_entry;
+
+ if (within_same_pool(slot, i, j))
+ swap_entry = entry + j - i;
+ else
+ swap_entry = get_rmap_list_entry(slot, j, 1);
+
+ swap_entries(entry, i, swap_entry, j);
+ if (!within_same_pool(slot, i, j))
+ put_rmap_list_entry(slot, j);
+ continue;
+
+skip_whole_pool:
+ i += PAGE_SIZE / sizeof(*entry);
+ if (i < slot->pages)
+ entry = get_rmap_list_entry(slot, i, 0);
+ continue;
+
+next_entry:
+ if (i >= slot->pages - 1 ||
+ !within_same_pool(slot, i, i + 1)) {
+ put_rmap_list_entry(slot, i);
+ if (i + 1 < slot->pages)
+ entry = get_rmap_list_entry(slot, i + 1, 0);
+ } else
+ entry++;
+ i++;
+ continue;
+ }
+
+ /* free empty pool entries which contain no rmap_item */
+ /* CAN be simplied to based on only pool_counts when bug freed !!!!! */
+ for (i = 0; i < slot->pool_size; i++) {
+ unsigned char has_rmap;
+ void *addr;
+
+ if (!slot->rmap_list_pool[i])
+ continue;
+
+ has_rmap = 0;
+ addr = kmap(slot->rmap_list_pool[i]);
+ BUG_ON(!addr);
+ for (j = 0; j < PAGE_SIZE / sizeof(*entry); j++) {
+ entry = (struct rmap_list_entry *)addr + j;
+ if (is_addr(entry->addr))
+ continue;
+ if (!entry->item)
+ continue;
+ has_rmap = 1;
+ }
+ kunmap(slot->rmap_list_pool[i]);
+ if (!has_rmap) {
+ BUG_ON(slot->pool_counts[i]);
+ __free_page(slot->rmap_list_pool[i]);
+ slot->rmap_list_pool[i] = NULL;
+ }
+ }
+
+ slot->flags &= ~UKSM_SLOT_NEED_SORT;
+}
+
+/*
+ * vma_fully_scanned() - if all the pages in this slot have been scanned.
+ */
+static inline int vma_fully_scanned(struct vma_slot *slot)
+{
+ return slot->pages_scanned == slot->pages;
+}
+
+/**
+ * get_next_rmap_item() - Get the next rmap_item in a vma_slot according to
+ * its random permutation. This function is embedded with the random
+ * permutation index management code.
+ */
+static struct rmap_item *get_next_rmap_item(struct vma_slot *slot, u32 *hash)
+{
+ unsigned long rand_range, addr, swap_index, scan_index;
+ struct rmap_item *item = NULL;
+ struct rmap_list_entry *scan_entry, *swap_entry = NULL;
+ struct page *page;
+
+ scan_index = swap_index = slot->pages_scanned % slot->pages;
+
+ if (pool_entry_boundary(scan_index))
+ try_free_last_pool(slot, scan_index - 1);
+
+ if (vma_fully_scanned(slot)) {
+ if (slot->flags & UKSM_SLOT_NEED_SORT)
+ slot->flags |= UKSM_SLOT_NEED_RERAND;
+ else
+ slot->flags &= ~UKSM_SLOT_NEED_RERAND;
+ if (slot->flags & UKSM_SLOT_NEED_SORT)
+ sort_rmap_entry_list(slot);
+ }
+
+ scan_entry = get_rmap_list_entry(slot, scan_index, 1);
+ if (!scan_entry)
+ return NULL;
+
+ if (entry_is_new(scan_entry)) {
+ scan_entry->addr = get_index_orig_addr(slot, scan_index);
+ set_is_addr(scan_entry->addr);
+ }
+
+ if (slot->flags & UKSM_SLOT_NEED_RERAND) {
+ rand_range = slot->pages - scan_index;
+ BUG_ON(!rand_range);
+ swap_index = scan_index + (prandom_u32() % rand_range);
+ }
+
+ if (swap_index != scan_index) {
+ swap_entry = get_rmap_list_entry(slot, swap_index, 1);
+
+ if (!swap_entry)
+ return NULL;
+
+ if (entry_is_new(swap_entry)) {
+ swap_entry->addr = get_index_orig_addr(slot,
+ swap_index);
+ set_is_addr(swap_entry->addr);
+ }
+ swap_entries(scan_entry, scan_index, swap_entry, swap_index);
+ }
+
+ addr = get_entry_address(scan_entry);
+ item = get_entry_item(scan_entry);
+ BUG_ON(addr > slot->vma->vm_end || addr < slot->vma->vm_start);
+
+ page = follow_page(slot->vma, addr, FOLL_GET);
+ if (IS_ERR_OR_NULL(page))
+ goto nopage;
+
+ if (!PageAnon(page))
+ goto putpage;
+
+ /*check is zero_page pfn or uksm_zero_page*/
+ if ((page_to_pfn(page) == zero_pfn)
+ || (page_to_pfn(page) == uksm_zero_pfn))
+ goto putpage;
+
+ flush_anon_page(slot->vma, page, addr);
+ flush_dcache_page(page);
+
+
+ *hash = page_hash(page, hash_strength, 1);
+ inc_uksm_pages_scanned();
+ /*if the page content all zero, re-map to zero-page*/
+ if (find_zero_page_hash(hash_strength, *hash)) {
+ if (!cmp_and_merge_zero_page(slot->vma, page)) {
+ slot->pages_merged++;
+
+ /* For full-zero pages, no need to create rmap item */
+ goto putpage;
+ } else {
+ inc_rshash_neg(memcmp_cost / 2);
+ }
+ }
+
+ if (!item) {
+ item = alloc_rmap_item();
+ if (item) {
+ /* It has already been zeroed */
+ item->slot = slot;
+ item->address = addr;
+ item->entry_index = scan_index;
+ scan_entry->item = item;
+ inc_rmap_list_pool_count(slot, scan_index);
+ } else
+ goto putpage;
+ }
+
+ BUG_ON(item->slot != slot);
+ /* the page may have changed */
+ item->page = page;
+ put_rmap_list_entry(slot, scan_index);
+ if (swap_entry)
+ put_rmap_list_entry(slot, swap_index);
+ return item;
+
+putpage:
+ put_page(page);
+ page = NULL;
+nopage:
+ /* no page, store addr back and free rmap_item if possible */
+ free_entry_item(scan_entry);
+ put_rmap_list_entry(slot, scan_index);
+ if (swap_entry)
+ put_rmap_list_entry(slot, swap_index);
+ return NULL;
+}
+
+static inline int in_stable_tree(struct rmap_item *rmap_item)
+{
+ return rmap_item->address & STABLE_FLAG;
+}
+
+/**
+ * scan_vma_one_page() - scan the next page in a vma_slot. Called with
+ * mmap_sem locked.
+ */
+static noinline void scan_vma_one_page(struct vma_slot *slot)
+{
+ u32 hash;
+ struct mm_struct *mm;
+ struct rmap_item *rmap_item = NULL;
+ struct vm_area_struct *vma = slot->vma;
+
+ mm = vma->vm_mm;
+ BUG_ON(!mm);
+ BUG_ON(!slot);
+
+ rmap_item = get_next_rmap_item(slot, &hash);
+ if (!rmap_item)
+ goto out1;
+
+ if (PageKsm(rmap_item->page) && in_stable_tree(rmap_item))
+ goto out2;
+
+ cmp_and_merge_page(rmap_item, hash);
+out2:
+ put_page(rmap_item->page);
+out1:
+ slot->pages_scanned++;
+ slot->this_sampled++;
+ if (slot->fully_scanned_round != fully_scanned_round)
+ scanned_virtual_pages++;
+
+ if (vma_fully_scanned(slot))
+ slot->fully_scanned_round = fully_scanned_round;
+}
+
+static inline unsigned long rung_get_pages(struct scan_rung *rung)
+{
+ struct slot_tree_node *node;
+
+ if (!rung->vma_root.rnode)
+ return 0;
+
+ node = container_of(rung->vma_root.rnode, struct slot_tree_node, snode);
+
+ return node->size;
+}
+
+#define RUNG_SAMPLED_MIN 3
+
+static inline
+void uksm_calc_rung_step(struct scan_rung *rung,
+ unsigned long page_time, unsigned long ratio)
+{
+ unsigned long sampled, pages;
+
+ /* will be fully scanned ? */
+ if (!rung->cover_msecs) {
+ rung->step = 1;
+ return;
+ }
+
+ sampled = rung->cover_msecs * (NSEC_PER_MSEC / TIME_RATIO_SCALE)
+ * ratio / page_time;
+
+ /*
+ * Before we finsish a scan round and expensive per-round jobs,
+ * we need to have a chance to estimate the per page time. So
+ * the sampled number can not be too small.
+ */
+ if (sampled < RUNG_SAMPLED_MIN)
+ sampled = RUNG_SAMPLED_MIN;
+
+ pages = rung_get_pages(rung);
+ if (likely(pages > sampled))
+ rung->step = pages / sampled;
+ else
+ rung->step = 1;
+}
+
+static inline int step_need_recalc(struct scan_rung *rung)
+{
+ unsigned long pages, stepmax;
+
+ pages = rung_get_pages(rung);
+ stepmax = pages / RUNG_SAMPLED_MIN;
+
+ return pages && (rung->step > pages ||
+ (stepmax && rung->step > stepmax));
+}
+
+static inline
+void reset_current_scan(struct scan_rung *rung, int finished, int step_recalc)
+{
+ struct vma_slot *slot;
+
+ if (finished)
+ rung->flags |= UKSM_RUNG_ROUND_FINISHED;
+
+ if (step_recalc || step_need_recalc(rung)) {
+ uksm_calc_rung_step(rung, uksm_ema_page_time, rung->cpu_ratio);
+ BUG_ON(step_need_recalc(rung));
+ }
+
+ slot_iter_index = prandom_u32() % rung->step;
+ BUG_ON(!rung->vma_root.rnode);
+ slot = sradix_tree_next(&rung->vma_root, NULL, 0, slot_iter);
+ BUG_ON(!slot);
+
+ rung->current_scan = slot;
+ rung->current_offset = slot_iter_index;
+}
+
+static inline struct sradix_tree_root *slot_get_root(struct vma_slot *slot)
+{
+ return &slot->rung->vma_root;
+}
+
+/*
+ * return if resetted.
+ */
+static int advance_current_scan(struct scan_rung *rung)
+{
+ unsigned short n;
+ struct vma_slot *slot, *next = NULL;
+
+ BUG_ON(!rung->vma_root.num);
+
+ slot = rung->current_scan;
+ n = (slot->pages - rung->current_offset) % rung->step;
+ slot_iter_index = rung->step - n;
+ next = sradix_tree_next(&rung->vma_root, slot->snode,
+ slot->sindex, slot_iter);
+
+ if (next) {
+ rung->current_offset = slot_iter_index;
+ rung->current_scan = next;
+ return 0;
+ } else {
+ reset_current_scan(rung, 1, 0);
+ return 1;
+ }
+}
+
+static inline void rung_rm_slot(struct vma_slot *slot)
+{
+ struct scan_rung *rung = slot->rung;
+ struct sradix_tree_root *root;
+
+ if (rung->current_scan == slot)
+ advance_current_scan(rung);
+
+ root = slot_get_root(slot);
+ sradix_tree_delete_from_leaf(root, slot->snode, slot->sindex);
+ slot->snode = NULL;
+ if (step_need_recalc(rung)) {
+ uksm_calc_rung_step(rung, uksm_ema_page_time, rung->cpu_ratio);
+ BUG_ON(step_need_recalc(rung));
+ }
+
+ /* In case advance_current_scan loop back to this slot again */
+ if (rung->vma_root.num && rung->current_scan == slot)
+ reset_current_scan(slot->rung, 1, 0);
+}
+
+static inline void rung_add_new_slots(struct scan_rung *rung,
+ struct vma_slot **slots, unsigned long num)
+{
+ int err;
+ struct vma_slot *slot;
+ unsigned long i;
+ struct sradix_tree_root *root = &rung->vma_root;
+
+ err = sradix_tree_enter(root, (void **)slots, num);
+ BUG_ON(err);
+
+ for (i = 0; i < num; i++) {
+ slot = slots[i];
+ slot->rung = rung;
+ BUG_ON(vma_fully_scanned(slot));
+ }
+
+ if (rung->vma_root.num == num)
+ reset_current_scan(rung, 0, 1);
+}
+
+static inline int rung_add_one_slot(struct scan_rung *rung,
+ struct vma_slot *slot)
+{
+ int err;
+
+ err = sradix_tree_enter(&rung->vma_root, (void **)&slot, 1);
+ if (err)
+ return err;
+
+ slot->rung = rung;
+ if (rung->vma_root.num == 1)
+ reset_current_scan(rung, 0, 1);
+
+ return 0;
+}
+
+/*
+ * Return true if the slot is deleted from its rung.
+ */
+static inline int vma_rung_enter(struct vma_slot *slot, struct scan_rung *rung)
+{
+ struct scan_rung *old_rung = slot->rung;
+ int err;
+
+ if (old_rung == rung)
+ return 0;
+
+ rung_rm_slot(slot);
+ err = rung_add_one_slot(rung, slot);
+ if (err) {
+ err = rung_add_one_slot(old_rung, slot);
+ WARN_ON(err); /* OOPS, badly OOM, we lost this slot */
+ }
+
+ return 1;
+}
+
+static inline int vma_rung_up(struct vma_slot *slot)
+{
+ struct scan_rung *rung;
+
+ rung = slot->rung;
+ if (slot->rung != &uksm_scan_ladder[SCAN_LADDER_SIZE-1])
+ rung++;
+
+ return vma_rung_enter(slot, rung);
+}
+
+static inline int vma_rung_down(struct vma_slot *slot)
+{
+ struct scan_rung *rung;
+
+ rung = slot->rung;
+ if (slot->rung != &uksm_scan_ladder[0])
+ rung--;
+
+ return vma_rung_enter(slot, rung);
+}
+
+/**
+ * cal_dedup_ratio() - Calculate the deduplication ratio for this slot.
+ */
+static unsigned long cal_dedup_ratio(struct vma_slot *slot)
+{
+ unsigned long ret;
+ unsigned long pages;
+
+ pages = slot->this_sampled;
+ if (!pages)
+ return 0;
+
+ BUG_ON(slot->pages_scanned == slot->last_scanned);
+
+ ret = slot->pages_merged;
+
+ /* Thrashing area filtering */
+ if (ret && uksm_thrash_threshold) {
+ if (slot->pages_cowed * 100 / slot->pages_merged
+ > uksm_thrash_threshold) {
+ ret = 0;
+ } else {
+ ret = slot->pages_merged - slot->pages_cowed;
+ }
+ }
+
+ return ret * 100 / pages;
+}
+
+/**
+ * cal_dedup_ratio() - Calculate the deduplication ratio for this slot.
+ */
+static unsigned long cal_dedup_ratio_old(struct vma_slot *slot)
+{
+ unsigned long ret;
+ unsigned long pages;
+
+ pages = slot->pages;
+ if (!pages)
+ return 0;
+
+ ret = slot->pages_bemerged;
+
+ /* Thrashing area filtering */
+ if (ret && uksm_thrash_threshold) {
+ if (slot->pages_cowed * 100 / slot->pages_bemerged
+ > uksm_thrash_threshold) {
+ ret = 0;
+ } else {
+ ret = slot->pages_bemerged - slot->pages_cowed;
+ }
+ }
+
+ return ret * 100 / pages;
+}
+
+/**
+ * stable_node_reinsert() - When the hash_strength has been adjusted, the
+ * stable tree need to be restructured, this is the function re-inserting the
+ * stable node.
+ */
+static inline void stable_node_reinsert(struct stable_node *new_node,
+ struct page *page,
+ struct rb_root *root_treep,
+ struct list_head *tree_node_listp,
+ u32 hash)
+{
+ struct rb_node **new = &root_treep->rb_node;
+ struct rb_node *parent = NULL;
+ struct stable_node *stable_node;
+ struct tree_node *tree_node;
+ struct page *tree_page;
+ int cmp;
+
+ while (*new) {
+ int cmp;
+
+ tree_node = rb_entry(*new, struct tree_node, node);
+
+ cmp = hash_cmp(hash, tree_node->hash);
+
+ if (cmp < 0) {
+ parent = *new;
+ new = &parent->rb_left;
+ } else if (cmp > 0) {
+ parent = *new;
+ new = &parent->rb_right;
+ } else
+ break;
+ }
+
+ if (*new) {
+ /* find a stable tree node with same first level hash value */
+ stable_node_hash_max(new_node, page, hash);
+ if (tree_node->count == 1) {
+ stable_node = rb_entry(tree_node->sub_root.rb_node,
+ struct stable_node, node);
+ tree_page = get_uksm_page(stable_node, 1, 0);
+ if (tree_page) {
+ stable_node_hash_max(stable_node,
+ tree_page, hash);
+ put_page(tree_page);
+
+ /* prepare for stable node insertion */
+
+ cmp = hash_cmp(new_node->hash_max,
+ stable_node->hash_max);
+ parent = &stable_node->node;
+ if (cmp < 0)
+ new = &parent->rb_left;
+ else if (cmp > 0)
+ new = &parent->rb_right;
+ else
+ goto failed;
+
+ goto add_node;
+ } else {
+ /* the only stable_node deleted, the tree node
+ * was not deleted.
+ */
+ goto tree_node_reuse;
+ }
+ }
+
+ /* well, search the collision subtree */
+ new = &tree_node->sub_root.rb_node;
+ parent = NULL;
+ BUG_ON(!*new);
+ while (*new) {
+ int cmp;
+
+ stable_node = rb_entry(*new, struct stable_node, node);
+
+ cmp = hash_cmp(new_node->hash_max,
+ stable_node->hash_max);
+
+ if (cmp < 0) {
+ parent = *new;
+ new = &parent->rb_left;
+ } else if (cmp > 0) {
+ parent = *new;
+ new = &parent->rb_right;
+ } else {
+ /* oh, no, still a collision */
+ goto failed;
+ }
+ }
+
+ goto add_node;
+ }
+
+ /* no tree node found */
+ tree_node = alloc_tree_node(tree_node_listp);
+ if (!tree_node) {
+ pr_err("UKSM: memory allocation error!\n");
+ goto failed;
+ } else {
+ tree_node->hash = hash;
+ rb_link_node(&tree_node->node, parent, new);
+ rb_insert_color(&tree_node->node, root_treep);
+
+tree_node_reuse:
+ /* prepare for stable node insertion */
+ parent = NULL;
+ new = &tree_node->sub_root.rb_node;
+ }
+
+add_node:
+ rb_link_node(&new_node->node, parent, new);
+ rb_insert_color(&new_node->node, &tree_node->sub_root);
+ new_node->tree_node = tree_node;
+ tree_node->count++;
+ return;
+
+failed:
+ /* This can only happen when two nodes have collided
+ * in two levels.
+ */
+ new_node->tree_node = NULL;
+ return;
+}
+
+static inline void free_all_tree_nodes(struct list_head *list)
+{
+ struct tree_node *node, *tmp;
+
+ list_for_each_entry_safe(node, tmp, list, all_list) {
+ free_tree_node(node);
+ }
+}
+
+/**
+ * stable_tree_delta_hash() - Delta hash the stable tree from previous hash
+ * strength to the current hash_strength. It re-structures the hole tree.
+ */
+static inline void stable_tree_delta_hash(u32 prev_hash_strength)
+{
+ struct stable_node *node, *tmp;
+ struct rb_root *root_new_treep;
+ struct list_head *new_tree_node_listp;
+
+ stable_tree_index = (stable_tree_index + 1) % 2;
+ root_new_treep = &root_stable_tree[stable_tree_index];
+ new_tree_node_listp = &stable_tree_node_list[stable_tree_index];
+ *root_new_treep = RB_ROOT;
+ BUG_ON(!list_empty(new_tree_node_listp));
+
+ /*
+ * we need to be safe, the node could be removed by get_uksm_page()
+ */
+ list_for_each_entry_safe(node, tmp, &stable_node_list, all_list) {
+ void *addr;
+ struct page *node_page;
+ u32 hash;
+
+ /*
+ * We are completely re-structuring the stable nodes to a new
+ * stable tree. We don't want to touch the old tree unlinks and
+ * old tree_nodes. The old tree_nodes will be freed at once.
+ */
+ node_page = get_uksm_page(node, 0, 0);
+ if (!node_page)
+ continue;
+
+ if (node->tree_node) {
+ hash = node->tree_node->hash;
+
+ addr = kmap_atomic(node_page);
+
+ hash = delta_hash(addr, prev_hash_strength,
+ hash_strength, hash);
+ kunmap_atomic(addr);
+ } else {
+ /*
+ *it was not inserted to rbtree due to collision in last
+ *round scan.
+ */
+ hash = page_hash(node_page, hash_strength, 0);
+ }
+
+ stable_node_reinsert(node, node_page, root_new_treep,
+ new_tree_node_listp, hash);
+ put_page(node_page);
+ }
+
+ root_stable_treep = root_new_treep;
+ free_all_tree_nodes(stable_tree_node_listp);
+ BUG_ON(!list_empty(stable_tree_node_listp));
+ stable_tree_node_listp = new_tree_node_listp;
+}
+
+static inline void inc_hash_strength(unsigned long delta)
+{
+ hash_strength += 1 << delta;
+ if (hash_strength > HASH_STRENGTH_MAX)
+ hash_strength = HASH_STRENGTH_MAX;
+}
+
+static inline void dec_hash_strength(unsigned long delta)
+{
+ unsigned long change = 1 << delta;
+
+ if (hash_strength <= change + 1)
+ hash_strength = 1;
+ else
+ hash_strength -= change;
+}
+
+static inline void inc_hash_strength_delta(void)
+{
+ hash_strength_delta++;
+ if (hash_strength_delta > HASH_STRENGTH_DELTA_MAX)
+ hash_strength_delta = HASH_STRENGTH_DELTA_MAX;
+}
+
+static inline unsigned long get_current_neg_ratio(void)
+{
+ u64 pos = benefit.pos;
+ u64 neg = benefit.neg;
+
+ if (!neg)
+ return 0;
+
+ if (!pos || neg > pos)
+ return 100;
+
+ if (neg > div64_u64(U64_MAX, 100))
+ pos = div64_u64(pos, 100);
+ else
+ neg *= 100;
+
+ return div64_u64(neg, pos);
+}
+
+static inline unsigned long get_current_benefit(void)
+{
+ u64 pos = benefit.pos;
+ u64 neg = benefit.neg;
+ u64 scanned = benefit.scanned;
+
+ if (neg > pos)
+ return 0;
+
+ return div64_u64((pos - neg), scanned);
+}
+
+static inline int judge_rshash_direction(void)
+{
+ u64 current_neg_ratio, stable_benefit;
+ u64 current_benefit, delta = 0;
+ int ret = STILL;
+
+ /*
+ * Try to probe a value after the boot, and in case the system
+ * are still for a long time.
+ */
+ if ((fully_scanned_round & 0xFFULL) == 10) {
+ ret = OBSCURE;
+ goto out;
+ }
+
+ current_neg_ratio = get_current_neg_ratio();
+
+ if (current_neg_ratio == 0) {
+ rshash_neg_cont_zero++;
+ if (rshash_neg_cont_zero > 2)
+ return GO_DOWN;
+ else
+ return STILL;
+ }
+ rshash_neg_cont_zero = 0;
+
+ if (current_neg_ratio > 90) {
+ ret = GO_UP;
+ goto out;
+ }
+
+ current_benefit = get_current_benefit();
+ stable_benefit = rshash_state.stable_benefit;
+
+ if (!stable_benefit) {
+ ret = OBSCURE;
+ goto out;
+ }
+
+ if (current_benefit > stable_benefit)
+ delta = current_benefit - stable_benefit;
+ else if (current_benefit < stable_benefit)
+ delta = stable_benefit - current_benefit;
+
+ delta = div64_u64(100 * delta, stable_benefit);
+
+ if (delta > 50) {
+ rshash_cont_obscure++;
+ if (rshash_cont_obscure > 2)
+ return OBSCURE;
+ else
+ return STILL;
+ }
+
+out:
+ rshash_cont_obscure = 0;
+ return ret;
+}
+
+/**
+ * rshash_adjust() - The main function to control the random sampling state
+ * machine for hash strength adapting.
+ *
+ * return true if hash_strength has changed.
+ */
+static inline int rshash_adjust(void)
+{
+ unsigned long prev_hash_strength = hash_strength;
+
+ if (!encode_benefit())
+ return 0;
+
+ switch (rshash_state.state) {
+ case RSHASH_STILL:
+ switch (judge_rshash_direction()) {
+ case GO_UP:
+ if (rshash_state.pre_direct == GO_DOWN)
+ hash_strength_delta = 0;
+
+ inc_hash_strength(hash_strength_delta);
+ inc_hash_strength_delta();
+ rshash_state.stable_benefit = get_current_benefit();
+ rshash_state.pre_direct = GO_UP;
+ break;
+
+ case GO_DOWN:
+ if (rshash_state.pre_direct == GO_UP)
+ hash_strength_delta = 0;
+
+ dec_hash_strength(hash_strength_delta);
+ inc_hash_strength_delta();
+ rshash_state.stable_benefit = get_current_benefit();
+ rshash_state.pre_direct = GO_DOWN;
+ break;
+
+ case OBSCURE:
+ rshash_state.stable_point = hash_strength;
+ rshash_state.turn_point_down = hash_strength;
+ rshash_state.turn_point_up = hash_strength;
+ rshash_state.turn_benefit_down = get_current_benefit();
+ rshash_state.turn_benefit_up = get_current_benefit();
+ rshash_state.lookup_window_index = 0;
+ rshash_state.state = RSHASH_TRYDOWN;
+ dec_hash_strength(hash_strength_delta);
+ inc_hash_strength_delta();
+ break;
+
+ case STILL:
+ break;
+ default:
+ BUG();
+ }
+ break;
+
+ case RSHASH_TRYDOWN:
+ if (rshash_state.lookup_window_index++ % 5 == 0)
+ rshash_state.below_count = 0;
+
+ if (get_current_benefit() < rshash_state.stable_benefit)
+ rshash_state.below_count++;
+ else if (get_current_benefit() >
+ rshash_state.turn_benefit_down) {
+ rshash_state.turn_point_down = hash_strength;
+ rshash_state.turn_benefit_down = get_current_benefit();
+ }
+
+ if (rshash_state.below_count >= 3 ||
+ judge_rshash_direction() == GO_UP ||
+ hash_strength == 1) {
+ hash_strength = rshash_state.stable_point;
+ hash_strength_delta = 0;
+ inc_hash_strength(hash_strength_delta);
+ inc_hash_strength_delta();
+ rshash_state.lookup_window_index = 0;
+ rshash_state.state = RSHASH_TRYUP;
+ hash_strength_delta = 0;
+ } else {
+ dec_hash_strength(hash_strength_delta);
+ inc_hash_strength_delta();
+ }
+ break;
+
+ case RSHASH_TRYUP:
+ if (rshash_state.lookup_window_index++ % 5 == 0)
+ rshash_state.below_count = 0;
+
+ if (get_current_benefit() < rshash_state.turn_benefit_down)
+ rshash_state.below_count++;
+ else if (get_current_benefit() > rshash_state.turn_benefit_up) {
+ rshash_state.turn_point_up = hash_strength;
+ rshash_state.turn_benefit_up = get_current_benefit();
+ }
+
+ if (rshash_state.below_count >= 3 ||
+ judge_rshash_direction() == GO_DOWN ||
+ hash_strength == HASH_STRENGTH_MAX) {
+ hash_strength = rshash_state.turn_benefit_up >
+ rshash_state.turn_benefit_down ?
+ rshash_state.turn_point_up :
+ rshash_state.turn_point_down;
+
+ rshash_state.state = RSHASH_PRE_STILL;
+ } else {
+ inc_hash_strength(hash_strength_delta);
+ inc_hash_strength_delta();
+ }
+
+ break;
+
+ case RSHASH_NEW:
+ case RSHASH_PRE_STILL:
+ rshash_state.stable_benefit = get_current_benefit();
+ rshash_state.state = RSHASH_STILL;
+ hash_strength_delta = 0;
+ break;
+ default:
+ BUG();
+ }
+
+ /* rshash_neg = rshash_pos = 0; */
+ reset_benefit();
+
+ if (prev_hash_strength != hash_strength)
+ stable_tree_delta_hash(prev_hash_strength);
+
+ return prev_hash_strength != hash_strength;
+}
+
+/**
+ * round_update_ladder() - The main function to do update of all the
+ * adjustments whenever a scan round is finished.
+ */
+static noinline void round_update_ladder(void)
+{
+ int i;
+ unsigned long dedup;
+ struct vma_slot *slot, *tmp_slot;
+
+ for (i = 0; i < SCAN_LADDER_SIZE; i++)
+ uksm_scan_ladder[i].flags &= ~UKSM_RUNG_ROUND_FINISHED;
+
+ list_for_each_entry_safe(slot, tmp_slot, &vma_slot_dedup, dedup_list) {
+
+ /* slot may be rung_rm_slot() when mm exits */
+ if (slot->snode) {
+ dedup = cal_dedup_ratio_old(slot);
+ if (dedup && dedup >= uksm_abundant_threshold)
+ vma_rung_up(slot);
+ }
+
+ slot->pages_bemerged = 0;
+ slot->pages_cowed = 0;
+
+ list_del_init(&slot->dedup_list);
+ }
+}
+
+static void uksm_del_vma_slot(struct vma_slot *slot)
+{
+ int i, j;
+ struct rmap_list_entry *entry;
+
+ if (slot->snode) {
+ /*
+ * In case it just failed when entering the rung, it's not
+ * necessary.
+ */
+ rung_rm_slot(slot);
+ }
+
+ if (!list_empty(&slot->dedup_list))
+ list_del(&slot->dedup_list);
+
+ if (!slot->rmap_list_pool || !slot->pool_counts) {
+ /* In case it OOMed in uksm_vma_enter() */
+ goto out;
+ }
+
+ for (i = 0; i < slot->pool_size; i++) {
+ void *addr;
+
+ if (!slot->rmap_list_pool[i])
+ continue;
+
+ addr = kmap(slot->rmap_list_pool[i]);
+ for (j = 0; j < PAGE_SIZE / sizeof(*entry); j++) {
+ entry = (struct rmap_list_entry *)addr + j;
+ if (is_addr(entry->addr))
+ continue;
+ if (!entry->item)
+ continue;
+
+ remove_rmap_item_from_tree(entry->item);
+ free_rmap_item(entry->item);
+ slot->pool_counts[i]--;
+ }
+ BUG_ON(slot->pool_counts[i]);
+ kunmap(slot->rmap_list_pool[i]);
+ __free_page(slot->rmap_list_pool[i]);
+ }
+ kfree(slot->rmap_list_pool);
+ kfree(slot->pool_counts);
+
+out:
+ slot->rung = NULL;
+ if (slot->flags & UKSM_SLOT_IN_UKSM) {
+ BUG_ON(uksm_pages_total < slot->pages);
+ uksm_pages_total -= slot->pages;
+ }
+
+ if (slot->fully_scanned_round == fully_scanned_round)
+ scanned_virtual_pages -= slot->pages;
+ else
+ scanned_virtual_pages -= slot->pages_scanned;
+ free_vma_slot(slot);
+}
+
+
+#define SPIN_LOCK_PERIOD 32
+static struct vma_slot *cleanup_slots[SPIN_LOCK_PERIOD];
+static inline void cleanup_vma_slots(void)
+{
+ struct vma_slot *slot;
+ int i;
+
+ i = 0;
+ spin_lock(&vma_slot_list_lock);
+ while (!list_empty(&vma_slot_del)) {
+ slot = list_entry(vma_slot_del.next,
+ struct vma_slot, slot_list);
+ list_del(&slot->slot_list);
+ cleanup_slots[i++] = slot;
+ if (i == SPIN_LOCK_PERIOD) {
+ spin_unlock(&vma_slot_list_lock);
+ while (--i >= 0)
+ uksm_del_vma_slot(cleanup_slots[i]);
+ i = 0;
+ spin_lock(&vma_slot_list_lock);
+ }
+ }
+ spin_unlock(&vma_slot_list_lock);
+
+ while (--i >= 0)
+ uksm_del_vma_slot(cleanup_slots[i]);
+}
+
+/*
+ * Expotional moving average formula
+ */
+static inline unsigned long ema(unsigned long curr, unsigned long last_ema)
+{
+ /*
+ * For a very high burst, even the ema cannot work well, a false very
+ * high per-page time estimation can result in feedback in very high
+ * overhead of context switch and rung update -- this will then lead
+ * to higher per-paper time, this may not converge.
+ *
+ * Instead, we try to approach this value in a binary manner.
+ */
+ if (curr > last_ema * 10)
+ return last_ema * 2;
+
+ return (EMA_ALPHA * curr + (100 - EMA_ALPHA) * last_ema) / 100;
+}
+
+/*
+ * convert cpu ratio in 1/TIME_RATIO_SCALE configured by user to
+ * nanoseconds based on current uksm_sleep_jiffies.
+ */
+static inline unsigned long cpu_ratio_to_nsec(unsigned int ratio)
+{
+ return NSEC_PER_USEC * jiffies_to_usecs(uksm_sleep_jiffies) /
+ (TIME_RATIO_SCALE - ratio) * ratio;
+}
+
+
+static inline unsigned long rung_real_ratio(int cpu_time_ratio)
+{
+ unsigned long ret;
+
+ BUG_ON(!cpu_time_ratio);
+
+ if (cpu_time_ratio > 0)
+ ret = cpu_time_ratio;
+ else
+ ret = (unsigned long)(-cpu_time_ratio) *
+ uksm_max_cpu_percentage / 100UL;
+
+ return ret ? ret : 1;
+}
+
+static noinline void uksm_calc_scan_pages(void)
+{
+ struct scan_rung *ladder = uksm_scan_ladder;
+ unsigned long sleep_usecs, nsecs;
+ unsigned long ratio;
+ int i;
+ unsigned long per_page;
+
+ if (uksm_ema_page_time > 100000 ||
+ (((unsigned long) uksm_eval_round & (256UL - 1)) == 0UL))
+ uksm_ema_page_time = UKSM_PAGE_TIME_DEFAULT;
+
+ per_page = uksm_ema_page_time;
+ BUG_ON(!per_page);
+
+ /*
+ * For every 8 eval round, we try to probe a uksm_sleep_jiffies value
+ * based on saved user input.
+ */
+ if (((unsigned long) uksm_eval_round & (8UL - 1)) == 0UL)
+ uksm_sleep_jiffies = uksm_sleep_saved;
+
+ /* We require a rung scan at least 1 page in a period. */
+ nsecs = per_page;
+ ratio = rung_real_ratio(ladder[0].cpu_ratio);
+ if (cpu_ratio_to_nsec(ratio) < nsecs) {
+ sleep_usecs = nsecs * (TIME_RATIO_SCALE - ratio) / ratio
+ / NSEC_PER_USEC;
+ uksm_sleep_jiffies = usecs_to_jiffies(sleep_usecs) + 1;
+ }
+
+ for (i = 0; i < SCAN_LADDER_SIZE; i++) {
+ ratio = rung_real_ratio(ladder[i].cpu_ratio);
+ ladder[i].pages_to_scan = cpu_ratio_to_nsec(ratio) /
+ per_page;
+ BUG_ON(!ladder[i].pages_to_scan);
+ uksm_calc_rung_step(&ladder[i], per_page, ratio);
+ }
+}
+
+/*
+ * From the scan time of this round (ns) to next expected min sleep time
+ * (ms), be careful of the possible overflows. ratio is taken from
+ * rung_real_ratio()
+ */
+static inline
+unsigned int scan_time_to_sleep(unsigned long long scan_time, unsigned long ratio)
+{
+ scan_time >>= 20; /* to msec level now */
+ BUG_ON(scan_time > (ULONG_MAX / TIME_RATIO_SCALE));
+
+ return (unsigned int) ((unsigned long) scan_time *
+ (TIME_RATIO_SCALE - ratio) / ratio);
+}
+
+#define __round_mask(x, y) ((__typeof__(x))((y)-1))
+#define round_up(x, y) ((((x)-1) | __round_mask(x, y))+1)
+
+static void uksm_vma_enter(struct vma_slot **slots, unsigned long num)
+{
+ struct scan_rung *rung;
+
+ rung = &uksm_scan_ladder[0];
+ rung_add_new_slots(rung, slots, num);
+}
+
+static struct vma_slot *batch_slots[SLOT_TREE_NODE_STORE_SIZE];
+
+static void uksm_enter_all_slots(void)
+{
+ struct vma_slot *slot;
+ unsigned long index;
+ struct list_head empty_vma_list;
+ int i;
+
+ i = 0;
+ index = 0;
+ INIT_LIST_HEAD(&empty_vma_list);
+
+ spin_lock(&vma_slot_list_lock);
+ while (!list_empty(&vma_slot_new)) {
+ slot = list_entry(vma_slot_new.next,
+ struct vma_slot, slot_list);
+
+ if (!slot->vma->anon_vma) {
+ list_move(&slot->slot_list, &empty_vma_list);
+ } else if (vma_can_enter(slot->vma)) {
+ batch_slots[index++] = slot;
+ list_del_init(&slot->slot_list);
+ } else {
+ list_move(&slot->slot_list, &vma_slot_noadd);
+ }
+
+ if (++i == SPIN_LOCK_PERIOD ||
+ (index && !(index % SLOT_TREE_NODE_STORE_SIZE))) {
+ spin_unlock(&vma_slot_list_lock);
+
+ if (index && !(index % SLOT_TREE_NODE_STORE_SIZE)) {
+ uksm_vma_enter(batch_slots, index);
+ index = 0;
+ }
+ i = 0;
+ cond_resched();
+ spin_lock(&vma_slot_list_lock);
+ }
+ }
+
+ list_splice(&empty_vma_list, &vma_slot_new);
+
+ spin_unlock(&vma_slot_list_lock);
+
+ if (index)
+ uksm_vma_enter(batch_slots, index);
+
+}
+
+static inline int rung_round_finished(struct scan_rung *rung)
+{
+ return rung->flags & UKSM_RUNG_ROUND_FINISHED;
+}
+
+static inline void judge_slot(struct vma_slot *slot)
+{
+ struct scan_rung *rung = slot->rung;
+ unsigned long dedup;
+ int deleted;
+
+ dedup = cal_dedup_ratio(slot);
+ if (vma_fully_scanned(slot) && uksm_thrash_threshold)
+ deleted = vma_rung_enter(slot, &uksm_scan_ladder[0]);
+ else if (dedup && dedup >= uksm_abundant_threshold)
+ deleted = vma_rung_up(slot);
+ else
+ deleted = vma_rung_down(slot);
+
+ slot->pages_merged = 0;
+ slot->pages_cowed = 0;
+ slot->this_sampled = 0;
+
+ if (vma_fully_scanned(slot))
+ slot->pages_scanned = 0;
+
+ slot->last_scanned = slot->pages_scanned;
+
+ /* If its deleted in above, then rung was already advanced. */
+ if (!deleted)
+ advance_current_scan(rung);
+}
+
+
+static inline int hash_round_finished(void)
+{
+ if (scanned_virtual_pages > (uksm_pages_total >> 2)) {
+ scanned_virtual_pages = 0;
+ if (uksm_pages_scanned)
+ fully_scanned_round++;
+
+ return 1;
+ } else {
+ return 0;
+ }
+}
+
+#define UKSM_MMSEM_BATCH 5
+#define BUSY_RETRY 100
+
+/**
+ * uksm_do_scan() - the main worker function.
+ */
+static noinline void uksm_do_scan(void)
+{
+ struct vma_slot *slot, *iter;
+ struct mm_struct *busy_mm;
+ unsigned char round_finished, all_rungs_emtpy;
+ int i, err, mmsem_batch;
+ unsigned long pcost;
+ long long delta_exec;
+ unsigned long vpages, max_cpu_ratio;
+ unsigned long long start_time, end_time, scan_time;
+ unsigned int expected_jiffies;
+
+ might_sleep();
+
+ vpages = 0;
+
+ start_time = task_sched_runtime(current);
+ max_cpu_ratio = 0;
+ mmsem_batch = 0;
+
+ for (i = 0; i < SCAN_LADDER_SIZE;) {
+ struct scan_rung *rung = &uksm_scan_ladder[i];
+ unsigned long ratio;
+ int busy_retry;
+
+ if (!rung->pages_to_scan) {
+ i++;
+ continue;
+ }
+
+ if (!rung->vma_root.num) {
+ rung->pages_to_scan = 0;
+ i++;
+ continue;
+ }
+
+ ratio = rung_real_ratio(rung->cpu_ratio);
+ if (ratio > max_cpu_ratio)
+ max_cpu_ratio = ratio;
+
+ busy_retry = BUSY_RETRY;
+ /*
+ * Do not consider rung_round_finished() here, just used up the
+ * rung->pages_to_scan quota.
+ */
+ while (rung->pages_to_scan && rung->vma_root.num &&
+ likely(!freezing(current))) {
+ int reset = 0;
+
+ slot = rung->current_scan;
+
+ BUG_ON(vma_fully_scanned(slot));
+
+ if (mmsem_batch)
+ err = 0;
+ else
+ err = try_down_read_slot_mmap_sem(slot);
+
+ if (err == -ENOENT) {
+rm_slot:
+ rung_rm_slot(slot);
+ continue;
+ }
+
+ busy_mm = slot->mm;
+
+ if (err == -EBUSY) {
+ /* skip other vmas on the same mm */
+ do {
+ reset = advance_current_scan(rung);
+ iter = rung->current_scan;
+ busy_retry--;
+ if (iter->vma->vm_mm != busy_mm ||
+ !busy_retry || reset)
+ break;
+ } while (1);
+
+ if (iter->vma->vm_mm != busy_mm) {
+ continue;
+ } else {
+ /* scan round finsished */
+ break;
+ }
+ }
+
+ BUG_ON(!vma_can_enter(slot->vma));
+ if (uksm_test_exit(slot->vma->vm_mm)) {
+ mmsem_batch = 0;
+ mmap_read_unlock(slot->vma->vm_mm);
+ goto rm_slot;
+ }
+
+ if (mmsem_batch)
+ mmsem_batch--;
+ else
+ mmsem_batch = UKSM_MMSEM_BATCH;
+
+ /* Ok, we have take the mmap_sem, ready to scan */
+ scan_vma_one_page(slot);
+ rung->pages_to_scan--;
+ vpages++;
+
+ if (rung->current_offset + rung->step > slot->pages - 1
+ || vma_fully_scanned(slot)) {
+ mmap_read_unlock(slot->vma->vm_mm);
+ judge_slot(slot);
+ mmsem_batch = 0;
+ } else {
+ rung->current_offset += rung->step;
+ if (!mmsem_batch)
+ mmap_read_unlock(slot->vma->vm_mm);
+ }
+
+ busy_retry = BUSY_RETRY;
+ cond_resched();
+ }
+
+ if (mmsem_batch) {
+ mmap_read_unlock(slot->vma->vm_mm);
+ mmsem_batch = 0;
+ }
+
+ if (freezing(current))
+ break;
+
+ cond_resched();
+ }
+ end_time = task_sched_runtime(current);
+ delta_exec = end_time - start_time;
+
+ if (freezing(current))
+ return;
+
+ cleanup_vma_slots();
+ uksm_enter_all_slots();
+
+ round_finished = 1;
+ all_rungs_emtpy = 1;
+ for (i = 0; i < SCAN_LADDER_SIZE; i++) {
+ struct scan_rung *rung = &uksm_scan_ladder[i];
+
+ if (rung->vma_root.num) {
+ all_rungs_emtpy = 0;
+ if (!rung_round_finished(rung))
+ round_finished = 0;
+ }
+ }
+
+ if (all_rungs_emtpy)
+ round_finished = 0;
+
+ if (round_finished) {
+ round_update_ladder();
+ uksm_eval_round++;
+
+ if (hash_round_finished() && rshash_adjust()) {
+ /* Reset the unstable root iff hash strength changed */
+ uksm_hash_round++;
+ root_unstable_tree = RB_ROOT;
+ free_all_tree_nodes(&unstable_tree_node_list);
+ }
+
+ /*
+ * A number of pages can hang around indefinitely on per-cpu
+ * pagevecs, raised page count preventing write_protect_page
+ * from merging them. Though it doesn't really matter much,
+ * it is puzzling to see some stuck in pages_volatile until
+ * other activity jostles them out, and they also prevented
+ * LTP's KSM test from succeeding deterministically; so drain
+ * them here (here rather than on entry to uksm_do_scan(),
+ * so we don't IPI too often when pages_to_scan is set low).
+ */
+ lru_add_drain_all();
+ }
+
+
+ if (vpages && delta_exec > 0) {
+ pcost = (unsigned long) delta_exec / vpages;
+ if (likely(uksm_ema_page_time))
+ uksm_ema_page_time = ema(pcost, uksm_ema_page_time);
+ else
+ uksm_ema_page_time = pcost;
+ }
+
+ uksm_calc_scan_pages();
+ uksm_sleep_real = uksm_sleep_jiffies;
+ /* in case of radical cpu bursts, apply the upper bound */
+ end_time = task_sched_runtime(current);
+ if (max_cpu_ratio && end_time > start_time) {
+ scan_time = end_time - start_time;
+ expected_jiffies = msecs_to_jiffies(
+ scan_time_to_sleep(scan_time, max_cpu_ratio));
+
+ if (expected_jiffies > uksm_sleep_real)
+ uksm_sleep_real = expected_jiffies;
+
+ /* We have a 1 second up bound for responsiveness. */
+ if (jiffies_to_msecs(uksm_sleep_real) > MSEC_PER_SEC)
+ uksm_sleep_real = msecs_to_jiffies(1000);
+ }
+
+ return;
+}
+
+static int ksmd_should_run(void)
+{
+ return uksm_run & UKSM_RUN_MERGE;
+}
+
+static int uksm_scan_thread(void *nothing)
+{
+ set_freezable();
+ set_user_nice(current, 5);
+
+ while (!kthread_should_stop()) {
+ mutex_lock(&uksm_thread_mutex);
+ if (ksmd_should_run())
+ uksm_do_scan();
+ mutex_unlock(&uksm_thread_mutex);
+
+ try_to_freeze();
+
+ if (ksmd_should_run()) {
+ schedule_timeout_interruptible(uksm_sleep_real);
+ uksm_sleep_times++;
+ } else {
+ wait_event_freezable(uksm_thread_wait,
+ ksmd_should_run() || kthread_should_stop());
+ }
+ }
+ return 0;
+}
+
+void rmap_walk_ksm(struct page *page, struct rmap_walk_control *rwc)
+{
+ struct stable_node *stable_node;
+ struct node_vma *node_vma;
+ struct rmap_item *rmap_item;
+ int search_new_forks = 0;
+ unsigned long address;
+
+ VM_BUG_ON_PAGE(!PageKsm(page), page);
+ VM_BUG_ON_PAGE(!PageLocked(page), page);
+
+ stable_node = page_stable_node(page);
+ if (!stable_node)
+ return;
+again:
+ hlist_for_each_entry(node_vma, &stable_node->hlist, hlist) {
+ hlist_for_each_entry(rmap_item, &node_vma->rmap_hlist, hlist) {
+ struct anon_vma *anon_vma = rmap_item->anon_vma;
+ struct anon_vma_chain *vmac;
+ struct vm_area_struct *vma;
+
+ cond_resched();
+ anon_vma_lock_read(anon_vma);
+ anon_vma_interval_tree_foreach(vmac, &anon_vma->rb_root,
+ 0, ULONG_MAX) {
+ cond_resched();
+ vma = vmac->vma;
+ address = get_rmap_addr(rmap_item);
+
+ if (address < vma->vm_start ||
+ address >= vma->vm_end)
+ continue;
+
+ if ((rmap_item->slot->vma == vma) ==
+ search_new_forks)
+ continue;
+
+ if (rwc->invalid_vma && rwc->invalid_vma(vma, rwc->arg))
+ continue;
+
+ if (!rwc->rmap_one(page, vma, address, rwc->arg)) {
+ anon_vma_unlock_read(anon_vma);
+ return;
+ }
+
+ if (rwc->done && rwc->done(page)) {
+ anon_vma_unlock_read(anon_vma);
+ return;
+ }
+ }
+ anon_vma_unlock_read(anon_vma);
+ }
+ }
+ if (!search_new_forks++)
+ goto again;
+}
+
+#ifdef CONFIG_MIGRATION
+/* Common ksm interface but may be specific to uksm */
+void ksm_migrate_page(struct page *newpage, struct page *oldpage)
+{
+ struct stable_node *stable_node;
+
+ VM_BUG_ON_PAGE(!PageLocked(oldpage), oldpage);
+ VM_BUG_ON_PAGE(!PageLocked(newpage), newpage);
+ VM_BUG_ON(newpage->mapping != oldpage->mapping);
+
+ stable_node = page_stable_node(newpage);
+ if (stable_node) {
+ VM_BUG_ON(stable_node->kpfn != page_to_pfn(oldpage));
+ stable_node->kpfn = page_to_pfn(newpage);
+ /*
+ * newpage->mapping was set in advance; now we need smp_wmb()
+ * to make sure that the new stable_node->kpfn is visible
+ * to get_ksm_page() before it can see that oldpage->mapping
+ * has gone stale (or that PageSwapCache has been cleared).
+ */
+ smp_wmb();
+ set_page_stable_node(oldpage, NULL);
+ }
+}
+#endif /* CONFIG_MIGRATION */
+
+#ifdef CONFIG_MEMORY_HOTREMOVE
+static struct stable_node *uksm_check_stable_tree(unsigned long start_pfn,
+ unsigned long end_pfn)
+{
+ struct rb_node *node;
+
+ for (node = rb_first(root_stable_treep); node; node = rb_next(node)) {
+ struct stable_node *stable_node;
+
+ stable_node = rb_entry(node, struct stable_node, node);
+ if (stable_node->kpfn >= start_pfn &&
+ stable_node->kpfn < end_pfn)
+ return stable_node;
+ }
+ return NULL;
+}
+
+static int uksm_memory_callback(struct notifier_block *self,
+ unsigned long action, void *arg)
+{
+ struct memory_notify *mn = arg;
+ struct stable_node *stable_node;
+
+ switch (action) {
+ case MEM_GOING_OFFLINE:
+ /*
+ * Keep it very simple for now: just lock out ksmd and
+ * MADV_UNMERGEABLE while any memory is going offline.
+ * mutex_lock_nested() is necessary because lockdep was alarmed
+ * that here we take uksm_thread_mutex inside notifier chain
+ * mutex, and later take notifier chain mutex inside
+ * uksm_thread_mutex to unlock it. But that's safe because both
+ * are inside mem_hotplug_mutex.
+ */
+ mutex_lock_nested(&uksm_thread_mutex, SINGLE_DEPTH_NESTING);
+ break;
+
+ case MEM_OFFLINE:
+ /*
+ * Most of the work is done by page migration; but there might
+ * be a few stable_nodes left over, still pointing to struct
+ * pages which have been offlined: prune those from the tree.
+ */
+ while ((stable_node = uksm_check_stable_tree(mn->start_pfn,
+ mn->start_pfn + mn->nr_pages)) != NULL)
+ remove_node_from_stable_tree(stable_node, 1, 1);
+ /* fallthrough */
+
+ case MEM_CANCEL_OFFLINE:
+ mutex_unlock(&uksm_thread_mutex);
+ break;
+ }
+ return NOTIFY_OK;
+}
+#endif /* CONFIG_MEMORY_HOTREMOVE */
+
+#ifdef CONFIG_SYSFS
+/*
+ * This all compiles without CONFIG_SYSFS, but is a waste of space.
+ */
+
+#define UKSM_ATTR_RO(_name) \
+ static struct kobj_attribute _name##_attr = __ATTR_RO(_name)
+#define UKSM_ATTR(_name) \
+ static struct kobj_attribute _name##_attr = \
+ __ATTR(_name, 0644, _name##_show, _name##_store)
+
+static ssize_t max_cpu_percentage_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ return sprintf(buf, "%u\n", uksm_max_cpu_percentage);
+}
+
+static ssize_t max_cpu_percentage_store(struct kobject *kobj,
+ struct kobj_attribute *attr,
+ const char *buf, size_t count)
+{
+ unsigned long max_cpu_percentage;
+ int err;
+
+ err = kstrtoul(buf, 10, &max_cpu_percentage);
+ if (err || max_cpu_percentage > 100)
+ return -EINVAL;
+
+ if (max_cpu_percentage == 100)
+ max_cpu_percentage = 99;
+ else if (max_cpu_percentage < 10)
+ max_cpu_percentage = 10;
+
+ uksm_max_cpu_percentage = max_cpu_percentage;
+
+ return count;
+}
+UKSM_ATTR(max_cpu_percentage);
+
+static ssize_t sleep_millisecs_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ return sprintf(buf, "%u\n", jiffies_to_msecs(uksm_sleep_jiffies));
+}
+
+static ssize_t sleep_millisecs_store(struct kobject *kobj,
+ struct kobj_attribute *attr,
+ const char *buf, size_t count)
+{
+ unsigned long msecs;
+ int err;
+
+ err = kstrtoul(buf, 10, &msecs);
+ if (err || msecs > MSEC_PER_SEC)
+ return -EINVAL;
+
+ uksm_sleep_jiffies = msecs_to_jiffies(msecs);
+ uksm_sleep_saved = uksm_sleep_jiffies;
+
+ return count;
+}
+UKSM_ATTR(sleep_millisecs);
+
+
+static ssize_t cpu_governor_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ int n = sizeof(uksm_cpu_governor_str) / sizeof(char *);
+ int i;
+
+ buf[0] = '\0';
+ for (i = 0; i < n ; i++) {
+ if (uksm_cpu_governor == i)
+ strcat(buf, "[");
+
+ strcat(buf, uksm_cpu_governor_str[i]);
+
+ if (uksm_cpu_governor == i)
+ strcat(buf, "]");
+
+ strcat(buf, " ");
+ }
+ strcat(buf, "\n");
+
+ return strlen(buf);
+}
+
+static inline void init_performance_values(void)
+{
+ int i;
+ struct scan_rung *rung;
+ struct uksm_cpu_preset_s *preset = uksm_cpu_preset + uksm_cpu_governor;
+
+
+ for (i = 0; i < SCAN_LADDER_SIZE; i++) {
+ rung = uksm_scan_ladder + i;
+ rung->cpu_ratio = preset->cpu_ratio[i];
+ rung->cover_msecs = preset->cover_msecs[i];
+ }
+
+ uksm_max_cpu_percentage = preset->max_cpu;
+}
+
+static ssize_t cpu_governor_store(struct kobject *kobj,
+ struct kobj_attribute *attr,
+ const char *buf, size_t count)
+{
+ int n = sizeof(uksm_cpu_governor_str) / sizeof(char *);
+
+ for (n--; n >= 0 ; n--) {
+ if (!strncmp(buf, uksm_cpu_governor_str[n],
+ strlen(uksm_cpu_governor_str[n])))
+ break;
+ }
+
+ if (n < 0)
+ return -EINVAL;
+ else
+ uksm_cpu_governor = n;
+
+ init_performance_values();
+
+ return count;
+}
+UKSM_ATTR(cpu_governor);
+
+static ssize_t run_show(struct kobject *kobj, struct kobj_attribute *attr,
+ char *buf)
+{
+ return sprintf(buf, "%u\n", uksm_run);
+}
+
+static ssize_t run_store(struct kobject *kobj, struct kobj_attribute *attr,
+ const char *buf, size_t count)
+{
+ int err;
+ unsigned long flags;
+
+ err = kstrtoul(buf, 10, &flags);
+ if (err || flags > UINT_MAX)
+ return -EINVAL;
+ if (flags > UKSM_RUN_MERGE)
+ return -EINVAL;
+
+ mutex_lock(&uksm_thread_mutex);
+ if (uksm_run != flags)
+ uksm_run = flags;
+ mutex_unlock(&uksm_thread_mutex);
+
+ if (flags & UKSM_RUN_MERGE)
+ wake_up_interruptible(&uksm_thread_wait);
+
+ return count;
+}
+UKSM_ATTR(run);
+
+static ssize_t abundant_threshold_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ return sprintf(buf, "%u\n", uksm_abundant_threshold);
+}
+
+static ssize_t abundant_threshold_store(struct kobject *kobj,
+ struct kobj_attribute *attr,
+ const char *buf, size_t count)
+{
+ int err;
+ unsigned long flags;
+
+ err = kstrtoul(buf, 10, &flags);
+ if (err || flags > 99)
+ return -EINVAL;
+
+ uksm_abundant_threshold = flags;
+
+ return count;
+}
+UKSM_ATTR(abundant_threshold);
+
+static ssize_t thrash_threshold_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ return sprintf(buf, "%u\n", uksm_thrash_threshold);
+}
+
+static ssize_t thrash_threshold_store(struct kobject *kobj,
+ struct kobj_attribute *attr,
+ const char *buf, size_t count)
+{
+ int err;
+ unsigned long flags;
+
+ err = kstrtoul(buf, 10, &flags);
+ if (err || flags > 99)
+ return -EINVAL;
+
+ uksm_thrash_threshold = flags;
+
+ return count;
+}
+UKSM_ATTR(thrash_threshold);
+
+static ssize_t cpu_ratios_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ int i, size;
+ struct scan_rung *rung;
+ char *p = buf;
+
+ for (i = 0; i < SCAN_LADDER_SIZE; i++) {
+ rung = &uksm_scan_ladder[i];
+
+ if (rung->cpu_ratio > 0)
+ size = sprintf(p, "%d ", rung->cpu_ratio);
+ else
+ size = sprintf(p, "MAX/%d ",
+ TIME_RATIO_SCALE / -rung->cpu_ratio);
+
+ p += size;
+ }
+
+ *p++ = '\n';
+ *p = '\0';
+
+ return p - buf;
+}
+
+static ssize_t cpu_ratios_store(struct kobject *kobj,
+ struct kobj_attribute *attr,
+ const char *buf, size_t count)
+{
+ int i, cpuratios[SCAN_LADDER_SIZE], err;
+ unsigned long value;
+ struct scan_rung *rung;
+ char *p, *end = NULL;
+
+ p = kzalloc(count, GFP_KERNEL);
+ if (!p)
+ return -ENOMEM;
+
+ memcpy(p, buf, count);
+
+ for (i = 0; i < SCAN_LADDER_SIZE; i++) {
+ if (i != SCAN_LADDER_SIZE - 1) {
+ end = strchr(p, ' ');
+ if (!end)
+ return -EINVAL;
+
+ *end = '\0';
+ }
+
+ if (strstr(p, "MAX/")) {
+ p = strchr(p, '/') + 1;
+ err = kstrtoul(p, 10, &value);
+ if (err || value > TIME_RATIO_SCALE || !value)
+ return -EINVAL;
+
+ cpuratios[i] = -(int) (TIME_RATIO_SCALE / value);
+ } else {
+ err = kstrtoul(p, 10, &value);
+ if (err || value > TIME_RATIO_SCALE || !value)
+ return -EINVAL;
+
+ cpuratios[i] = value;
+ }
+
+ p = end + 1;
+ }
+
+ for (i = 0; i < SCAN_LADDER_SIZE; i++) {
+ rung = &uksm_scan_ladder[i];
+
+ rung->cpu_ratio = cpuratios[i];
+ }
+
+ return count;
+}
+UKSM_ATTR(cpu_ratios);
+
+static ssize_t eval_intervals_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ int i, size;
+ struct scan_rung *rung;
+ char *p = buf;
+
+ for (i = 0; i < SCAN_LADDER_SIZE; i++) {
+ rung = &uksm_scan_ladder[i];
+ size = sprintf(p, "%u ", rung->cover_msecs);
+ p += size;
+ }
+
+ *p++ = '\n';
+ *p = '\0';
+
+ return p - buf;
+}
+
+static ssize_t eval_intervals_store(struct kobject *kobj,
+ struct kobj_attribute *attr,
+ const char *buf, size_t count)
+{
+ int i, err;
+ unsigned long values[SCAN_LADDER_SIZE];
+ struct scan_rung *rung;
+ char *p, *end = NULL;
+ ssize_t ret = count;
+
+ p = kzalloc(count + 2, GFP_KERNEL);
+ if (!p)
+ return -ENOMEM;
+
+ memcpy(p, buf, count);
+
+ for (i = 0; i < SCAN_LADDER_SIZE; i++) {
+ if (i != SCAN_LADDER_SIZE - 1) {
+ end = strchr(p, ' ');
+ if (!end) {
+ ret = -EINVAL;
+ goto out;
+ }
+
+ *end = '\0';
+ }
+
+ err = kstrtoul(p, 10, &values[i]);
+ if (err) {
+ ret = -EINVAL;
+ goto out;
+ }
+
+ p = end + 1;
+ }
+
+ for (i = 0; i < SCAN_LADDER_SIZE; i++) {
+ rung = &uksm_scan_ladder[i];
+
+ rung->cover_msecs = values[i];
+ }
+
+out:
+ kfree(p);
+ return ret;
+}
+UKSM_ATTR(eval_intervals);
+
+static ssize_t ema_per_page_time_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ return sprintf(buf, "%lu\n", uksm_ema_page_time);
+}
+UKSM_ATTR_RO(ema_per_page_time);
+
+static ssize_t pages_shared_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ return sprintf(buf, "%lu\n", uksm_pages_shared);
+}
+UKSM_ATTR_RO(pages_shared);
+
+static ssize_t pages_sharing_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ return sprintf(buf, "%lu\n", uksm_pages_sharing);
+}
+UKSM_ATTR_RO(pages_sharing);
+
+static ssize_t pages_unshared_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ return sprintf(buf, "%lu\n", uksm_pages_unshared);
+}
+UKSM_ATTR_RO(pages_unshared);
+
+static ssize_t full_scans_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ return sprintf(buf, "%llu\n", fully_scanned_round);
+}
+UKSM_ATTR_RO(full_scans);
+
+static ssize_t pages_scanned_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ unsigned long base = 0;
+ u64 delta, ret;
+
+ if (pages_scanned_stored) {
+ base = pages_scanned_base;
+ ret = pages_scanned_stored;
+ delta = uksm_pages_scanned >> base;
+ if (CAN_OVERFLOW_U64(ret, delta)) {
+ ret >>= 1;
+ delta >>= 1;
+ base++;
+ ret += delta;
+ }
+ } else {
+ ret = uksm_pages_scanned;
+ }
+
+ while (ret > ULONG_MAX) {
+ ret >>= 1;
+ base++;
+ }
+
+ if (base)
+ return sprintf(buf, "%lu * 2^%lu\n", (unsigned long)ret, base);
+ else
+ return sprintf(buf, "%lu\n", (unsigned long)ret);
+}
+UKSM_ATTR_RO(pages_scanned);
+
+static ssize_t hash_strength_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ return sprintf(buf, "%lu\n", hash_strength);
+}
+UKSM_ATTR_RO(hash_strength);
+
+static ssize_t sleep_times_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ return sprintf(buf, "%llu\n", uksm_sleep_times);
+}
+UKSM_ATTR_RO(sleep_times);
+
+
+static struct attribute *uksm_attrs[] = {
+ &max_cpu_percentage_attr.attr,
+ &sleep_millisecs_attr.attr,
+ &cpu_governor_attr.attr,
+ &run_attr.attr,
+ &ema_per_page_time_attr.attr,
+ &pages_shared_attr.attr,
+ &pages_sharing_attr.attr,
+ &pages_unshared_attr.attr,
+ &full_scans_attr.attr,
+ &pages_scanned_attr.attr,
+ &hash_strength_attr.attr,
+ &sleep_times_attr.attr,
+ &thrash_threshold_attr.attr,
+ &abundant_threshold_attr.attr,
+ &cpu_ratios_attr.attr,
+ &eval_intervals_attr.attr,
+ NULL,
+};
+
+static struct attribute_group uksm_attr_group = {
+ .attrs = uksm_attrs,
+ .name = "uksm",
+};
+#endif /* CONFIG_SYSFS */
+
+static inline void init_scan_ladder(void)
+{
+ int i;
+ struct scan_rung *rung;
+
+ for (i = 0; i < SCAN_LADDER_SIZE; i++) {
+ rung = uksm_scan_ladder + i;
+ slot_tree_init_root(&rung->vma_root);
+ }
+
+ init_performance_values();
+ uksm_calc_scan_pages();
+}
+
+static inline int cal_positive_negative_costs(void)
+{
+ struct page *p1, *p2;
+ unsigned char *addr1, *addr2;
+ unsigned long i, time_start, hash_cost;
+ unsigned long loopnum = 0;
+
+ /*IMPORTANT: volatile is needed to prevent over-optimization by gcc. */
+ volatile u32 hash;
+ volatile int ret;
+
+ p1 = alloc_page(GFP_KERNEL);
+ if (!p1)
+ return -ENOMEM;
+
+ p2 = alloc_page(GFP_KERNEL);
+ if (!p2)
+ return -ENOMEM;
+
+ addr1 = kmap_atomic(p1);
+ addr2 = kmap_atomic(p2);
+ memset(addr1, prandom_u32(), PAGE_SIZE);
+ memcpy(addr2, addr1, PAGE_SIZE);
+
+ /* make sure that the two pages differ in last byte */
+ addr2[PAGE_SIZE-1] = ~addr2[PAGE_SIZE-1];
+ kunmap_atomic(addr2);
+ kunmap_atomic(addr1);
+
+ time_start = jiffies;
+ while (jiffies - time_start < 100) {
+ for (i = 0; i < 100; i++)
+ hash = page_hash(p1, HASH_STRENGTH_FULL, 0);
+ loopnum += 100;
+ }
+ hash_cost = (jiffies - time_start);
+
+ time_start = jiffies;
+ for (i = 0; i < loopnum; i++)
+ ret = pages_identical_with_cost(p1, p2);
+ memcmp_cost = HASH_STRENGTH_FULL * (jiffies - time_start);
+ memcmp_cost /= hash_cost;
+ pr_info("UKSM: relative memcmp_cost = %lu "
+ "hash=%u cmp_ret=%d.\n",
+ memcmp_cost, hash, ret);
+
+ __free_page(p1);
+ __free_page(p2);
+ return 0;
+}
+
+static int init_zeropage_hash_table(void)
+{
+ struct page *page;
+ char *addr;
+ int i;
+
+ page = alloc_page(GFP_KERNEL);
+ if (!page)
+ return -ENOMEM;
+
+ addr = kmap_atomic(page);
+ memset(addr, 0, PAGE_SIZE);
+ kunmap_atomic(addr);
+
+ zero_hash_table = kmalloc_array(HASH_STRENGTH_MAX, sizeof(u32),
+ GFP_KERNEL);
+ if (!zero_hash_table)
+ return -ENOMEM;
+
+ for (i = 0; i < HASH_STRENGTH_MAX; i++)
+ zero_hash_table[i] = page_hash(page, i, 0);
+
+ __free_page(page);
+
+ return 0;
+}
+
+static inline int init_random_sampling(void)
+{
+ unsigned long i;
+
+ random_nums = kmalloc(PAGE_SIZE, GFP_KERNEL);
+ if (!random_nums)
+ return -ENOMEM;
+
+ for (i = 0; i < HASH_STRENGTH_FULL; i++)
+ random_nums[i] = i;
+
+ for (i = 0; i < HASH_STRENGTH_FULL; i++) {
+ unsigned long rand_range, swap_index, tmp;
+
+ rand_range = HASH_STRENGTH_FULL - i;
+ swap_index = i + prandom_u32() % rand_range;
+ tmp = random_nums[i];
+ random_nums[i] = random_nums[swap_index];
+ random_nums[swap_index] = tmp;
+ }
+
+ rshash_state.state = RSHASH_NEW;
+ rshash_state.below_count = 0;
+ rshash_state.lookup_window_index = 0;
+
+ return cal_positive_negative_costs();
+}
+
+static int __init uksm_slab_init(void)
+{
+ rmap_item_cache = UKSM_KMEM_CACHE(rmap_item, 0);
+ if (!rmap_item_cache)
+ goto out;
+
+ stable_node_cache = UKSM_KMEM_CACHE(stable_node, 0);
+ if (!stable_node_cache)
+ goto out_free1;
+
+ node_vma_cache = UKSM_KMEM_CACHE(node_vma, 0);
+ if (!node_vma_cache)
+ goto out_free2;
+
+ vma_slot_cache = UKSM_KMEM_CACHE(vma_slot, 0);
+ if (!vma_slot_cache)
+ goto out_free3;
+
+ tree_node_cache = UKSM_KMEM_CACHE(tree_node, 0);
+ if (!tree_node_cache)
+ goto out_free4;
+
+ return 0;
+
+out_free4:
+ kmem_cache_destroy(vma_slot_cache);
+out_free3:
+ kmem_cache_destroy(node_vma_cache);
+out_free2:
+ kmem_cache_destroy(stable_node_cache);
+out_free1:
+ kmem_cache_destroy(rmap_item_cache);
+out:
+ return -ENOMEM;
+}
+
+static void __init uksm_slab_free(void)
+{
+ kmem_cache_destroy(stable_node_cache);
+ kmem_cache_destroy(rmap_item_cache);
+ kmem_cache_destroy(node_vma_cache);
+ kmem_cache_destroy(vma_slot_cache);
+ kmem_cache_destroy(tree_node_cache);
+}
+
+/* Common interface to ksm, different to it. */
+int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
+ unsigned long end, int advice, unsigned long *vm_flags)
+{
+ int err;
+
+ switch (advice) {
+ case MADV_MERGEABLE:
+ return 0; /* just ignore the advice */
+
+ case MADV_UNMERGEABLE:
+ if (!(*vm_flags & VM_MERGEABLE) || !uksm_flags_can_scan(*vm_flags))
+ return 0; /* just ignore the advice */
+
+ if (vma->anon_vma) {
+ err = unmerge_uksm_pages(vma, start, end);
+ if (err)
+ return err;
+ }
+
+ uksm_remove_vma(vma);
+ *vm_flags &= ~VM_MERGEABLE;
+ break;
+ }
+
+ return 0;
+}
+
+/* Common interface to ksm, actually the same. */
+struct page *ksm_might_need_to_copy(struct page *page,
+ struct vm_area_struct *vma, unsigned long address)
+{
+ struct anon_vma *anon_vma = page_anon_vma(page);
+ struct page *new_page;
+
+ if (PageKsm(page)) {
+ if (page_stable_node(page))
+ return page; /* no need to copy it */
+ } else if (!anon_vma) {
+ return page; /* no need to copy it */
+ } else if (anon_vma->root == vma->anon_vma->root &&
+ page->index == linear_page_index(vma, address)) {
+ return page; /* still no need to copy it */
+ }
+ if (!PageUptodate(page))
+ return page; /* let do_swap_page report the error */
+
+ new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, address);
+ if (new_page) {
+ copy_user_highpage(new_page, page, address, vma);
+
+ SetPageDirty(new_page);
+ __SetPageUptodate(new_page);
+ __SetPageLocked(new_page);
+ }
+
+ return new_page;
+}
+
+/* Copied from mm/ksm.c and required from 5.1 */
+bool reuse_ksm_page(struct page *page,
+ struct vm_area_struct *vma,
+ unsigned long address)
+{
+#ifdef CONFIG_DEBUG_VM
+ if (WARN_ON(is_zero_pfn(page_to_pfn(page))) ||
+ WARN_ON(!page_mapped(page)) ||
+ WARN_ON(!PageLocked(page))) {
+ dump_page(page, "reuse_ksm_page");
+ return false;
+ }
+#endif
+
+ if (PageSwapCache(page) || !page_stable_node(page))
+ return false;
+ /* Prohibit parallel get_ksm_page() */
+ if (!page_ref_freeze(page, 1))
+ return false;
+
+ page_move_anon_rmap(page, vma);
+ page->index = linear_page_index(vma, address);
+ page_ref_unfreeze(page, 1);
+
+ return true;
+}
+
+static int __init uksm_init(void)
+{
+ struct task_struct *uksm_thread;
+ int err;
+
+ uksm_sleep_jiffies = msecs_to_jiffies(100);
+ uksm_sleep_saved = uksm_sleep_jiffies;
+
+ slot_tree_init();
+ init_scan_ladder();
+
+
+ err = init_random_sampling();
+ if (err)
+ goto out_free2;
+
+ err = uksm_slab_init();
+ if (err)
+ goto out_free1;
+
+ err = init_zeropage_hash_table();
+ if (err)
+ goto out_free0;
+
+ uksm_thread = kthread_run(uksm_scan_thread, NULL, "uksmd");
+ if (IS_ERR(uksm_thread)) {
+ pr_err("uksm: creating kthread failed\n");
+ err = PTR_ERR(uksm_thread);
+ goto out_free;
+ }
+
+#ifdef CONFIG_SYSFS
+ err = sysfs_create_group(mm_kobj, &uksm_attr_group);
+ if (err) {
+ pr_err("uksm: register sysfs failed\n");
+ kthread_stop(uksm_thread);
+ goto out_free;
+ }
+#else
+ uksm_run = UKSM_RUN_MERGE; /* no way for user to start it */
+
+#endif /* CONFIG_SYSFS */
+
+#ifdef CONFIG_MEMORY_HOTREMOVE
+ /*
+ * Choose a high priority since the callback takes uksm_thread_mutex:
+ * later callbacks could only be taking locks which nest within that.
+ */
+ hotplug_memory_notifier(uksm_memory_callback, 100);
+#endif
+ return 0;
+
+out_free:
+ kfree(zero_hash_table);
+out_free0:
+ uksm_slab_free();
+out_free1:
+ kfree(random_nums);
+out_free2:
+ kfree(uksm_scan_ladder);
+ return err;
+}
+
+#ifdef MODULE
+subsys_initcall(ksm_init);
+#else
+late_initcall(uksm_init);
+#endif
+
diff --git a/mm/vmstat.c b/mm/vmstat.c
index 8ce262034..c0bc68578 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1237,6 +1237,9 @@ const char * const vmstat_text[] = {
"nr_swapcached",
#endif
+#ifdef CONFIG_UKSM
+ "nr_uksm_zero_pages",
+#endif
/* enum writeback_stat_item counters */
"nr_dirty_threshold",
"nr_dirty_background_threshold",
--
2.33.1.711.g9d530dc002
