The patch titled
Subject: slab, slub: remove size disparity on debug kernel
has been added to the -mm tree. Its filename is
slab-slub-remove-size-disparity-on-debug-kernel.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/slab-slub-remove-size-disparity-on-debug-kernel.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/slab-slub-remove-size-disparity-on-debug-kernel.patch
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From: Shakeel Butt <shakeelb@xxxxxxxxxx>
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 <active_objs> <num_objs> <objsize> <objperslab> <pagesperslab> ...
radix_tree_node 15052 15075 4096 1 1 ...
$cat /cgroup/memory/temp/memory.kmem.slabinfo | grep radix
name <active_objs> <num_objs> <objsize> <objperslab> <pagesperslab> ...
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@xxxxxxxxxx
Signed-off-by: Shakeel Butt <shakeelb@xxxxxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
Cc: Pekka Enberg <penberg@xxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: Vladimir Davydov <vdavydov.dev@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/slab_common.c | 9 ++++-----
1 file changed, 4 insertions(+), 5 deletions(-)
diff -puN mm/slab_common.c~slab-slub-remove-size-disparity-on-debug-kernel mm/slab_common.c
--- a/mm/slab_common.c~slab-slub-remove-size-disparity-on-debug-kernel
+++ a/mm/slab_common.c
@@ -379,7 +379,7 @@ struct kmem_cache *find_mergeable(unsign
}
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(c
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 *n
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_
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);
_
Patches currently in -mm which might be from shakeelb@xxxxxxxxxx are
slab-slub-remove-size-disparity-on-debug-kernel.patch
mm-memcg-remote-memcg-charging-for-kmem-allocations.patch
fs-fsnotify-account-fsnotify-metadata-to-kmemcg.patch
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