From: Joonsoo Kim Date: Fri, 28 Oct 2016 00:46:18 +0000 (-0700) Subject: mm/slab: fix kmemcg cache creation delayed issue X-Git-Url: http://git.cdn.openwrt.org/?a=commitdiff_plain;h=86d9f48534e800e4d62cdc1b5aaf539f4c1d47d6;p=openwrt%2Fstaging%2Fblogic.git mm/slab: fix kmemcg cache creation delayed issue 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.kim@lge.com Reported-by: Doug Smythies Tested-by: Doug Smythies Signed-off-by: Joonsoo Kim Cc: Christoph Lameter Cc: Pekka Enberg Cc: David Rientjes Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/mm/slab.c b/mm/slab.c index 090fb26b3a39..c451e3f6bbf6 100644 --- a/mm/slab.c +++ b/mm/slab.c @@ -966,7 +966,7 @@ static int setup_kmem_cache_node(struct kmem_cache *cachep, * 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: