From c3ac9a8ade65ccbfd145fbff895ae8d8d62d09b0 Mon Sep 17 00:00:00 2001 From: Johannes Weiner Date: Tue, 29 May 2012 15:06:25 -0700 Subject: mm: memcg: count pte references from every member of the reclaimed hierarchy The rmap walker checking page table references has historically ignored references from VMAs that were not part of the memcg that was being reclaimed during memcg hard limit reclaim. When transitioning global reclaim to memcg hierarchy reclaim, I missed that bit and now references from outside a memcg are ignored even during global reclaim. Reverting back to traditional behaviour - count all references during global reclaim and only mind references of the memcg being reclaimed during limit reclaim would be one option. However, the more generic idea is to ignore references exactly then when they are outside the hierarchy that is currently under reclaim; because only then will their reclamation be of any use to help the pressure situation. It makes no sense to ignore references from a sibling memcg and then evict a page that will be immediately refaulted by that sibling which contributes to the same usage of the common ancestor under reclaim. The solution: make the rmap walker ignore references from VMAs that are not part of the hierarchy that is being reclaimed. Flat limit reclaim will stay the same, hierarchical limit reclaim will mind the references only to pages that the hierarchy owns. Global reclaim, since it reclaims from all memcgs, will be fixed to regard all references. [akpm@linux-foundation.org: name the args in the declaration] Signed-off-by: Johannes Weiner Reported-by: Konstantin Khlebnikov Acked-by: Konstantin Khlebnikov Cc: KAMEZAWA Hiroyuki Acked-by: Michal Hocko Cc: Li Zefan Cc: Li Zefan Cc: Tejun Heo Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/vmscan.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) (limited to 'mm/vmscan.c') diff --git a/mm/vmscan.c b/mm/vmscan.c index 68e5819d0f1b..8fffc65a84de 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -645,7 +645,8 @@ static enum page_references page_check_references(struct page *page, int referenced_ptes, referenced_page; unsigned long vm_flags; - referenced_ptes = page_referenced(page, 1, mz->mem_cgroup, &vm_flags); + referenced_ptes = page_referenced(page, 1, sc->target_mem_cgroup, + &vm_flags); referenced_page = TestClearPageReferenced(page); /* @@ -1513,7 +1514,8 @@ static void shrink_active_list(unsigned long nr_to_scan, } } - if (page_referenced(page, 0, mz->mem_cgroup, &vm_flags)) { + if (page_referenced(page, 0, sc->target_mem_cgroup, + &vm_flags)) { nr_rotated += hpage_nr_pages(page); /* * Identify referenced, file-backed active pages and -- cgit v1.2.1