From: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> Subject: 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 quitely. 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@xxxxxxx Reported-by: Doug Smythies <dsmythies@xxxxxxxxx> Tested-by: Doug Smythies <dsmythies@xxxxxxxxx> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> Cc: Christoph Lameter <cl@xxxxxxxxx> Cc: Pekka Enberg <penberg@xxxxxxxxxx> Cc: David Rientjes <rientjes@xxxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/slab.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff -puN mm/slab.c~mm-slab-fix-kmemcg-cache-creation-delayed-issue mm/slab.c --- a/mm/slab.c~mm-slab-fix-kmemcg-cache-creation-delayed-issue +++ a/mm/slab.c @@ -966,7 +966,7 @@ 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: _ -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html