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authorAndrea Arcangeli <aarcange@redhat.com>2010-08-09 17:19:08 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2010-08-09 20:44:58 -0700
commitba6f0ff3981e6263ab81ac512f04cca55b85ec81 (patch)
tree0052d4551de72731be503c8d78949a330ba865ed /include/linux/ksm.h
parent26ba0cb63cb8df4e45394227f33c938920b11b88 (diff)
downloadlinux-linaro-stable-ba6f0ff3981e6263ab81ac512f04cca55b85ec81.tar.gz
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 <aarcange@redhat.com> Signed-off-by: Rik van Riel <riel@redhat.com> Cc: Izik Eidus <ieidus@yahoo.com> Cc: Avi Kivity <avi@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/ksm.h')
-rw-r--r--include/linux/ksm.h2
1 files changed, 1 insertions, 1 deletions
diff --git a/include/linux/ksm.h b/include/linux/ksm.h
index 43bdab769fc3..74d691ee9121 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;