The patch titled
ksm: break cow once unshared
has been added to the -mm tree. Its filename is
ksm-break-cow-once-unshared.patch
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------------------------------------------------------
Subject: ksm: break cow once unshared
From: Hugh Dickins <hugh.dickins@xxxxxxxxxxxxx>
We kept agreeing not to bother about the unswappable shared KSM pages
which later become unshared by others: observation suggests they're not
a significant proportion. But they are disadvantageous, and it is easier
to break COW to replace them by swappable pages, than offer statistics
to show that they don't matter; then we can stop worrying about them.
Doing this in ksm_do_scan, they don't go through cmp_and_merge_page on
this pass: give them a good chance of getting into the unstable tree
on the next pass, or back into the stable, by computing checksum now.
Signed-off-by: Hugh Dickins <hugh.dickins@xxxxxxxxxxxxx>
Acked-by: Izik Eidus <ieidus@xxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/ksm.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff -puN mm/ksm.c~ksm-break-cow-once-unshared mm/ksm.c
--- a/mm/ksm.c~ksm-break-cow-once-unshared
+++ a/mm/ksm.c
@@ -1275,6 +1275,14 @@ static void ksm_do_scan(unsigned int sca
return;
if (!PageKsm(page) || !in_stable_tree(rmap_item))
cmp_and_merge_page(page, rmap_item);
+ else if (page_mapcount(page) == 1) {
+ /*
+ * Replace now-unshared ksm page by ordinary page.
+ */
+ break_cow(rmap_item->mm, rmap_item->address);
+ remove_rmap_item_from_tree(rmap_item);
+ rmap_item->oldchecksum = calc_checksum(page);
+ }
put_page(page);
}
}
_
Patches currently in -mm which might be from hugh.dickins@xxxxxxxxxxxxx are
acpi-fix-null-bug-for-hid-uid-string.patch
mm-oom-analysis-add-shmem-vmstat.patch
ksm-add-mmu_notifier-set_pte_at_notify.patch
ksm-first-tidy-up-madvise_vma.patch
ksm-define-madv_mergeable-and-madv_unmergeable.patch
ksm-the-mm-interface-to-ksm.patch
ksm-no-debug-in-page_dup_rmap.patch
ksm-identify-pageksm-pages.patch
ksm-kernel-samepage-merging.patch
ksm-prevent-mremap-move-poisoning.patch
ksm-change-copyright-message.patch
ksm-change-ksm-nice-level-to-be-5.patch
ksm-rename-kernel_pages_allocated.patch
ksm-move-pages_sharing-updates.patch
ksm-pages_unshared-and-pages_volatile.patch
ksm-break-cow-once-unshared.patch
ksm-keep-quiet-while-list-empty.patch
ksm-five-little-cleanups.patch
ksm-fix-endless-loop-on-oom.patch
ksm-distribute-remove_mm_from_lists.patch
ksm-fix-oom-deadlock.patch
ksm-sysfs-and-defaults.patch
ksm-add-some-documentation.patch
ksm-remove-vm_mergeable_flags.patch
getrusage-fill-ru_maxrss-value.patch
getrusage-fill-ru_maxrss-value-update.patch
ramfs-move-ramfs_magic-to-include-linux-magich.patch
memory-controller-soft-limit-organize-cgroups-v9-fix.patch
prio_tree-debugging-patch.patch
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