4.8-stable review patch. If anyone has any objections, please let me know.
------------------ From: Joonsoo Kim <iamjoonsoo....@lge.com> commit 86d9f48534e800e4d62cdc1b5aaf539f4c1d47d6 upstream. There is a bug report that SLAB makes extreme load average due to over 2000 kworker thread. https://bugzilla.kernel.org/show_bug.cgi?id=172981 This issue is caused by kmemcg feature that try to create new set of kmem_caches for each memcg. Recently, kmem_cache creation is slowed by synchronize_sched() and futher kmem_cache creation is also delayed since kmem_cache creation is synchronized by a global slab_mutex lock. So, the number of kworker that try to create kmem_cache increases quietly. synchronize_sched() is for lockless access to node's shared array but it's not needed when a new kmem_cache is created. So, this patch rules out that case. Fixes: 801faf0db894 ("mm/slab: lockless decision to grow cache") Link: http://lkml.kernel.org/r/1475734855-4837-1-git-send-email-iamjoonsoo....@lge.com Reported-by: Doug Smythies <dsmyth...@telus.net> Tested-by: Doug Smythies <dsmyth...@telus.net> Signed-off-by: Joonsoo Kim <iamjoonsoo....@lge.com> Cc: Christoph Lameter <c...@linux.com> Cc: Pekka Enberg <penb...@kernel.org> Cc: David Rientjes <rient...@google.com> Signed-off-by: Andrew Morton <a...@linux-foundation.org> Signed-off-by: Linus Torvalds <torva...@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org> --- mm/slab.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/mm/slab.c +++ b/mm/slab.c @@ -964,7 +964,7 @@ static int setup_kmem_cache_node(struct * guaranteed to be valid until irq is re-enabled, because it will be * freed after synchronize_sched(). */ - if (force_change) + if (old_shared && force_change) synchronize_sched(); fail:
