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author | Shakeel Butt <shakeelb@google.com> | 2018-04-06 01:21:57 +0200 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2018-04-06 06:36:24 +0200 |
commit | f9e13c0a5a33d1eaec374d6d4dab53a4f72756a0 (patch) | |
tree | 25020c64a2d657fe1fd0d002c5b59352e4a3e870 /mm/slub.c | |
parent | mm/slab_common.c: remove test if cache name is accessible (diff) | |
download | linux-f9e13c0a5a33d1eaec374d6d4dab53a4f72756a0.tar.xz linux-f9e13c0a5a33d1eaec374d6d4dab53a4f72756a0.zip |
slab, slub: skip unnecessary kasan_cache_shutdown()
The kasan quarantine is designed to delay freeing slab objects to catch
use-after-free. The quarantine can be large (several percent of machine
memory size). When kmem_caches are deleted related objects are flushed
from the quarantine but this requires scanning the entire quarantine
which can be very slow. We have seen the kernel busily working on this
while holding slab_mutex and badly affecting cache_reaper, slabinfo
readers and memcg kmem cache creations.
It can easily reproduced by following script:
yes . | head -1000000 | xargs stat > /dev/null
for i in `seq 1 10`; do
seq 500 | (cd /cg/memory && xargs mkdir)
seq 500 | xargs -I{} sh -c 'echo $BASHPID > \
/cg/memory/{}/tasks && exec stat .' > /dev/null
seq 500 | (cd /cg/memory && xargs rmdir)
done
The busy stack:
kasan_cache_shutdown
shutdown_cache
memcg_destroy_kmem_caches
mem_cgroup_css_free
css_free_rwork_fn
process_one_work
worker_thread
kthread
ret_from_fork
This patch is based on the observation that if the kmem_cache to be
destroyed is empty then there should not be any objects of this cache in
the quarantine.
Without the patch the script got stuck for couple of hours. With the
patch the script completed within a second.
Link: http://lkml.kernel.org/r/20180327230603.54721-1-shakeelb@google.com
Signed-off-by: Shakeel Butt <shakeelb@google.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Acked-by: Christoph Lameter <cl@linux.com>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/slub.c')
-rw-r--r-- | mm/slub.c | 11 |
1 files changed, 11 insertions, 0 deletions
diff --git a/mm/slub.c b/mm/slub.c index f48d942a487e..4fb037c98782 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -3696,6 +3696,17 @@ static void free_partial(struct kmem_cache *s, struct kmem_cache_node *n) discard_slab(s, page); } +bool __kmem_cache_empty(struct kmem_cache *s) +{ + int node; + struct kmem_cache_node *n; + + for_each_kmem_cache_node(s, node, n) + if (n->nr_partial || slabs_node(s, node)) + return false; + return true; +} + /* * Release all resources used by a slab cache. */ |