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mm: slab: optimize memcg_slab_free_hook()

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Most callers of memcg_slab_free_hook() already know the slab,  which could
be passed to memcg_slab_free_hook() directly to reduce the overhead of an
another call of virt_to_slab().  For bulk freeing of objects, the call of
slab_objcgs() in the loop in memcg_slab_free_hook() is redundant as well.
Rework memcg_slab_free_hook() and build_detached_freelist() to reduce
those unnecessary overhead and make memcg_slab_free_hook() can handle bulk
freeing in slab_free().

Move the calling site of memcg_slab_free_hook() from do_slab_free() to
slab_free() for slub to make the code clearer since the logic is weird
(e.g. the caller need to judge whether it needs to call
memcg_slab_free_hook()). It is easy to make mistakes like missing calling
of memcg_slab_free_hook() like fixes of:

  commit d1b2cf6cb8 ("mm: memcg/slab: uncharge during kmem_cache_free_bulk()")
  commit ae085d7f93 ("mm: kfence: fix missing objcg housekeeping for SLAB")

This optimization is mainly for bulk objects freeing.  The following numbers
is shown for 16-object freeing.

                           before      after
  kmem_cache_free_bulk:   ~430 ns     ~400 ns

The overhead is reduced by about 7% for 16-object freeing.

Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Reviewed-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Link: https://lore.kernel.org/r/20220429123044.37885-1-songmuchun@bytedance.com
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
This commit is contained in:
Muchun Song 2022-04-29 20:30:44 +08:00 • committed by Vlastimil Babka
parent b347aa7b57
commit b77d5b1b83
3 changed files with 32 additions and 68 deletions
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4
mm/slab.c
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@ -3406,9 +3406,10 @@ static __always_inline void __cache_free(struct kmem_cache *cachep, void *objp,
{
bool init;
memcg_slab_free_hook(cachep, virt_to_slab(objp), &objp, 1);
if (is_kfence_address(objp)) {
kmemleak_free_recursive(objp, cachep->flags);
memcg_slab_free_hook(cachep, &objp, 1);
__kfence_free(objp);
return;
}
@ -3441,7 +3442,6 @@ void ___cache_free(struct kmem_cache *cachep, void *objp,
check_irq_off();
kmemleak_free_recursive(objp, cachep->flags);
objp = cache_free_debugcheck(cachep, objp, caller);
memcg_slab_free_hook(cachep, &objp, 1);
/*
* Skip calling cache_free_alien() when the platform is not numa.