diff options
Diffstat (limited to 'system/easy-kernel/0402-mm-optimise-slub.patch')
| -rw-r--r-- | system/easy-kernel/0402-mm-optimise-slub.patch | 84 |
1 files changed, 84 insertions, 0 deletions
diff --git a/system/easy-kernel/0402-mm-optimise-slub.patch b/system/easy-kernel/0402-mm-optimise-slub.patch new file mode 100644 index 000000000..83a5ccb52 --- /dev/null +++ b/system/easy-kernel/0402-mm-optimise-slub.patch @@ -0,0 +1,84 @@ +From: Jay Patel <jaypatel@linux.ibm.com> +Date: Thu, 20 Jul 2023 15:53:37 +0530 +Subject: [PATCH 14/16] mm/slub: Optimize slub memory usage + +In the current implementation of the slub memory allocator, the slab +order selection process follows these criteria: + +1) Determine the minimum order required to serve the minimum number of +objects (min_objects). This calculation is based on the formula (order += min_objects * object_size / PAGE_SIZE). +2) If the minimum order is greater than the maximum allowed order +(slub_max_order), set slub_max_order as the order for this slab. +3) If the minimum order is less than the slub_max_order, iterate +through a loop from minimum order to slub_max_order and check if the +condition (rem <= slab_size / fract_leftover) holds true. Here, +slab_size is calculated as (PAGE_SIZE << order), rem is (slab_size % +object_size), and fract_leftover can have values of 16, 8, or 4. If +the condition is true, select that order for the slab. + +However, in point 3, when calculating the fraction left over, it can +result in a large range of values (like 1 Kb to 256 bytes on 4K page +size & 4 Kb to 16 Kb on 64K page size with order 0 and goes on +increasing with higher order) when compared to the remainder (rem). This +can lead to the selection of an order that results in more memory +wastage. To mitigate such wastage, we have modified point 3 as follows: +To adjust the value of fract_leftover based on the page size, while +retaining the current value as the default for a 4K page size. + +Signed-off-by: Jay Patel <jaypatel@linux.ibm.com> +--- + mm/slub.c | 17 +++++++---------- + 1 file changed, 7 insertions(+), 10 deletions(-) + +diff --git a/mm/slub.c b/mm/slub.c +index f79400481..3cf4842d5 100644 +--- a/mm/slub.c ++++ b/mm/slub.c +@@ -287,6 +287,7 @@ static inline bool kmem_cache_has_cpu_partial(struct kmem_cache *s) + #define OO_SHIFT 16 + #define OO_MASK ((1 << OO_SHIFT) - 1) + #define MAX_OBJS_PER_PAGE 32767 /* since slab.objects is u15 */ ++#define SLUB_PAGE_FRAC_SHIFT 12 + + /* Internal SLUB flags */ + /* Poison object */ +@@ -4140,6 +4141,7 @@ static inline int calculate_order(unsigned int size) + unsigned int min_objects; + unsigned int max_objects; + unsigned int nr_cpus; ++ unsigned int page_size_frac; + + /* + * Attempt to find best configuration for a slab. This +@@ -4168,10 +4170,13 @@ static inline int calculate_order(unsigned int size) + max_objects = order_objects(slub_max_order, size); + min_objects = min(min_objects, max_objects); + +- while (min_objects > 1) { ++ page_size_frac = ((PAGE_SIZE >> SLUB_PAGE_FRAC_SHIFT) == 1) ? 0 ++ : PAGE_SIZE >> SLUB_PAGE_FRAC_SHIFT; ++ ++ while (min_objects >= 1) { + unsigned int fraction; + +- fraction = 16; ++ fraction = 16 + page_size_frac; + while (fraction >= 4) { + order = calc_slab_order(size, min_objects, + slub_max_order, fraction); +@@ -4182,14 +4187,6 @@ static inline int calculate_order(unsigned int size) + min_objects--; + } + +- /* +- * We were unable to place multiple objects in a slab. Now +- * lets see if we can place a single object there. +- */ +- order = calc_slab_order(size, 1, slub_max_order, 1); +- if (order <= slub_max_order) +- return order; +- + /* + * Doh this slab cannot be placed using slub_max_order. + */ |