On Wed, Feb 29, 2012 at 09:39:46AM +0900, KAMEZAWA Hiroyuki wrote:

On Tue, 28 Feb 2012 15:14:49 +0100
Johannes Weiner [off-list ref] wrote:

quoted

--- a/mm/vmscan.c
+++ b/mm/vmscan.c

@@ -708,7 +708,8 @@ 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);

I'm sorry if I don't understand the codes... !sc->target_mem_cgroup case is handled ?

Yes, but it's not obvious from the diff alone.  page_referenced() does
this:

		/*
		 * If we are reclaiming on behalf of a cgroup, skip
		 * counting on behalf of references from different
		 * cgroups
		 */
		if (memcg && !mm_match_cgroup(vma->vm_mm, memcg))
			continue;

As a result, !sc->target_mem_cgroup -- global reclaim -- will never
ignore references, or put differently, respect references from all
memcgs, which is what we want.

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