The patch titled
Subject: mm/ksm: documentation for coloured zero pages deduplication
has been added to the -mm tree. Its filename is
mm-ksm-improve-deduplication-of-zero-pages-with-colouring-fix-2.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-ksm-improve-deduplication-of-zero-pages-with-colouring-fix-2.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-ksm-improve-deduplication-of-zero-pages-with-colouring-fix-2.patch
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------------------------------------------------------
From: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxxxxxxx>
Subject: mm/ksm: documentation for coloured zero pages deduplication
This patch adds the needed documentation for the use_zero_pages property.
Link: http://lkml.kernel.org/r/1484927522-1964-1-git-send-email-imbrenda@xxxxxxxxxxxxxxxxxx
Signed-off-by: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxxxxxxx>
Cc: Christian Borntraeger <borntraeger@xxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
Documentation/vm/ksm.txt | 14 ++++++++++++++
1 file changed, 14 insertions(+)
diff -puN Documentation/vm/ksm.txt~mm-ksm-improve-deduplication-of-zero-pages-with-colouring-fix-2 Documentation/vm/ksm.txt
--- a/Documentation/vm/ksm.txt~mm-ksm-improve-deduplication-of-zero-pages-with-colouring-fix-2
+++ a/Documentation/vm/ksm.txt
@@ -80,6 +80,20 @@ run - set 0 to stop ksmd fr
Default: 0 (must be changed to 1 to activate KSM,
except if CONFIG_SYSFS is disabled)
+use_zero_pages - specifies whether empty pages (i.e. allocated pages
+ that only contain zeroes) should be treated specially.
+ When set to 1, empty pages are merged with the kernel
+ zero page(s) instead of with each other as it would
+ happen normally. This can improve the performance on
+ architectures with coloured zero pages, depending on
+ the workload. Care should be taken when enabling this
+ setting, as it can potentially degrade the performance
+ of KSM for some workloads, for example if the checksums
+ of pages candidate for merging match the checksum of
+ an empty page. This setting can be changed at any time,
+ it is only effective for pages merged after the change.
+ Default: 0 (normal KSM behaviour as in earlier releases)
+
The effectiveness of KSM and MADV_MERGEABLE is shown in /sys/kernel/mm/ksm/:
pages_shared - how many shared pages are being used
_
Patches currently in -mm which might be from imbrenda@xxxxxxxxxxxxxxxxxx are
mm-ksm-improve-deduplication-of-zero-pages-with-colouring.patch
mm-ksm-improve-deduplication-of-zero-pages-with-colouring-fix-2.patch
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