Messages in this thread | | | Subject | Re: [PATCH] slab, slub: skip unnecessary kasan_cache_shutdown() | From | Andrey Ryabinin <> | Date | Wed, 28 Mar 2018 20:03:20 +0300 |
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On 03/28/2018 02:06 AM, Shakeel Butt wrote: > 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. > > Signed-off-by: Shakeel Butt <shakeelb@google.com> >
Acked-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
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