From 4138fdfc8b5db5a7a4b9b50c69d475fb2ac351b7 Mon Sep 17 00:00:00 2001 From: Roman Gushchin Date: Thu, 6 Aug 2020 23:20:42 -0700 Subject: mm: slub: implement SLUB version of obj_to_index() This commit implements SLUB version of the obj_to_index() function, which will be required to calculate the offset of obj_cgroup in the obj_cgroups vector to store/obtain the objcg ownership data. To make it faster, let's repeat the SLAB's trick introduced by commit 6a2d7a955d8d ("SLAB: use a multiply instead of a divide in obj_to_index()") and avoid an expensive division. Vlastimil Babka noticed, that SLUB does have already a similar function called slab_index(), which is defined only if SLUB_DEBUG is enabled. The function does a similar math, but with a division, and it also takes a page address instead of a page pointer. Let's remove slab_index() and replace it with the new helper __obj_to_index(), which takes a page address. obj_to_index() will be a simple wrapper taking a page pointer and passing page_address(page) into __obj_to_index(). Signed-off-by: Roman Gushchin Signed-off-by: Andrew Morton Reviewed-by: Vlastimil Babka Reviewed-by: Shakeel Butt Acked-by: Johannes Weiner Cc: Christoph Lameter Cc: Michal Hocko Cc: Tejun Heo Link: http://lkml.kernel.org/r/20200623174037.3951353-5-guro@fb.com Signed-off-by: Linus Torvalds --- include/linux/slub_def.h | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) (limited to 'include/linux/slub_def.h') diff --git a/include/linux/slub_def.h b/include/linux/slub_def.h index d2153789bd9f..30e91c83d401 100644 --- a/include/linux/slub_def.h +++ b/include/linux/slub_def.h @@ -8,6 +8,7 @@ * (C) 2007 SGI, Christoph Lameter */ #include +#include enum stat_item { ALLOC_FASTPATH, /* Allocation from cpu slab */ @@ -86,6 +87,7 @@ struct kmem_cache { unsigned long min_partial; unsigned int size; /* The size of an object including metadata */ unsigned int object_size;/* The size of an object without metadata */ + struct reciprocal_value reciprocal_size; unsigned int offset; /* Free pointer offset */ #ifdef CONFIG_SLUB_CPU_PARTIAL /* Number of per cpu partial objects to keep around */ @@ -182,4 +184,18 @@ static inline void *nearest_obj(struct kmem_cache *cache, struct page *page, return result; } +/* Determine object index from a given position */ +static inline unsigned int __obj_to_index(const struct kmem_cache *cache, + void *addr, void *obj) +{ + return reciprocal_divide(kasan_reset_tag(obj) - addr, + cache->reciprocal_size); +} + +static inline unsigned int obj_to_index(const struct kmem_cache *cache, + const struct page *page, void *obj) +{ + return __obj_to_index(cache, page_address(page), obj); +} + #endif /* _LINUX_SLUB_DEF_H */ -- cgit v1.2.3