From 613a5eb5677923fdaecfa582738c7bcf80abe186 Mon Sep 17 00:00:00 2001 From: Shakeel Butt Date: Thu, 5 Apr 2018 16:21:50 -0700 Subject: slab, slub: remove size disparity on debug kernel I have noticed on debug kernel with SLAB, the size of some non-root slabs were larger than their corresponding root slabs. e.g. for radix_tree_node: $cat /proc/slabinfo | grep radix name ... radix_tree_node 15052 15075 4096 1 1 ... $cat /cgroup/memory/temp/memory.kmem.slabinfo | grep radix name ... radix_tree_node 1581 158 4120 1 2 ... However for SLUB in debug kernel, the sizes were same. On further inspection it is found that SLUB always use kmem_cache.object_size to measure the kmem_cache.size while SLAB use the given kmem_cache.size. In the debug kernel the slab's size can be larger than its object_size. Thus in the creation of non-root slab, the SLAB uses the root's size as base to calculate the non-root slab's size and thus non-root slab's size can be larger than the root slab's size. For SLUB, the non-root slab's size is measured based on the root's object_size and thus the size will remain same for root and non-root slab. This patch makes slab's object_size the default base to measure the slab's size. Link: http://lkml.kernel.org/r/20180313165428.58699-1-shakeelb@google.com Fixes: 794b1248be4e ("memcg, slab: separate memcg vs root cache creation paths") Signed-off-by: Shakeel Butt Cc: Christoph Lameter Cc: Pekka Enberg Cc: David Rientjes Cc: Joonsoo Kim Cc: Vladimir Davydov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/slab_common.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) (limited to 'mm/slab_common.c') diff --git a/mm/slab_common.c b/mm/slab_common.c index e2e2485b3496..4a4bd71ab728 100644 --- a/mm/slab_common.c +++ b/mm/slab_common.c @@ -379,7 +379,7 @@ struct kmem_cache *find_mergeable(unsigned int size, unsigned int align, } static struct kmem_cache *create_cache(const char *name, - unsigned int object_size, unsigned int size, unsigned int align, + unsigned int object_size, unsigned int align, slab_flags_t flags, unsigned int useroffset, unsigned int usersize, void (*ctor)(void *), struct mem_cgroup *memcg, struct kmem_cache *root_cache) @@ -396,8 +396,7 @@ static struct kmem_cache *create_cache(const char *name, goto out; s->name = name; - s->object_size = object_size; - s->size = size; + s->size = s->object_size = object_size; s->align = align; s->ctor = ctor; s->useroffset = useroffset; @@ -503,7 +502,7 @@ kmem_cache_create_usercopy(const char *name, goto out_unlock; } - s = create_cache(cache_name, size, size, + s = create_cache(cache_name, size, calculate_alignment(flags, align, size), flags, useroffset, usersize, ctor, NULL, NULL); if (IS_ERR(s)) { @@ -650,7 +649,7 @@ void memcg_create_kmem_cache(struct mem_cgroup *memcg, goto out_unlock; s = create_cache(cache_name, root_cache->object_size, - root_cache->size, root_cache->align, + root_cache->align, root_cache->flags & CACHE_CREATE_MASK, root_cache->useroffset, root_cache->usersize, root_cache->ctor, memcg, root_cache); -- cgit v1.2.3-55-g7522