From ba6f0ff3981e6263ab81ac512f04cca55b85ec81 Mon Sep 17 00:00:00 2001 From: Andrea Arcangeli Date: Mon, 9 Aug 2010 17:19:08 -0700 Subject: [PATCH] ksm: fix ksm swapin time optimization The new anon-vma code, was suboptimal and it lead to erratic invocation of ksm_does_need_to_copy. That leads to host hangs or guest vnc lockup, or weird behavior. It's unclear why ksm_does_need_to_copy is unstable but the point is that when KSM is not in use, ksm_does_need_to_copy must never run or we bounce pages for no good reason. I suspect the same hangs will happen with KVM swaps. But this at least fixes the regression in the new-anon-vma code and it only let KSM bugs triggers when KSM is in use. The code in do_swap_page likely doesn't cope well with a not-swapcache, especially the memcg code. Signed-off-by: Andrea Arcangeli Signed-off-by: Rik van Riel Cc: Izik Eidus Cc: Avi Kivity Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/ksm.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/include/linux/ksm.h b/include/linux/ksm.h index 43bdab7..74d691e 100644 --- a/include/linux/ksm.h +++ b/include/linux/ksm.h @@ -78,7 +78,7 @@ static inline struct page *ksm_might_need_to_copy(struct page *page, struct anon_vma *anon_vma = page_anon_vma(page); if (!anon_vma || - (anon_vma == vma->anon_vma && + (anon_vma->root == vma->anon_vma->root && page->index == linear_page_index(vma, address))) return page; -- 2.7.4