From: Johannes Weiner Date: Tue, 15 Mar 2016 21:57:58 +0000 (-0700) Subject: mm: memcontrol: drop unnecessary lru locking from mem_cgroup_migrate() X-Git-Tag: v4.6-rc1~137^2~17 X-Git-Url: https://git.kernelconcepts.de/?a=commitdiff_plain;h=9cf7666ace654cc50f815e95f0415e3fcdd6fcfe;p=karo-tx-linux.git mm: memcontrol: drop unnecessary lru locking from mem_cgroup_migrate() Migration accounting in the memory controller used to have to handle both oldpage and newpage being on the LRU already; fuse's page cache replacement used to pass a recycled newpage that had been uncharged but not freed and removed from the LRU, and the memcg migration code used to uncharge oldpage to "pass on" the existing charge to newpage. Nowadays, pages are no longer uncharged when truncated from the page cache, but rather only at free time, so if a LRU page is recycled in page cache replacement it'll also still be charged. And we bail out of the charge transfer altogether in that case. Tell commit_charge() that we know newpage is not on the LRU, to avoid taking the zone->lru_lock unnecessarily from the migration path. But also, oldpage is no longer uncharged inside migration. We only use oldpage for its page->mem_cgroup and page size, so we don't care about its LRU state anymore either. Remove any mention from the kernel doc. Signed-off-by: Johannes Weiner Suggested-by: Hugh Dickins Acked-by: Vladimir Davydov Acked-by: Michal Hocko Cc: Mateusz Guzik Cc: Sergey Senozhatsky Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 3e4199830456..42882c1e7fce 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -5489,7 +5489,6 @@ void mem_cgroup_uncharge_list(struct list_head *page_list) * be uncharged upon free. * * Both pages must be locked, @newpage->mapping must be set up. - * Either or both pages might be on the LRU already. */ void mem_cgroup_migrate(struct page *oldpage, struct page *newpage) { @@ -5524,7 +5523,7 @@ void mem_cgroup_migrate(struct page *oldpage, struct page *newpage) page_counter_charge(&memcg->memsw, nr_pages); css_get_many(&memcg->css, nr_pages); - commit_charge(newpage, memcg, true); + commit_charge(newpage, memcg, false); local_irq_disable(); mem_cgroup_charge_statistics(memcg, newpage, compound, nr_pages);