Messages in this thread Patch in this message | | | Date | Mon, 30 Nov 2009 09:13:16 +0900 | From | KAMEZAWA Hiroyuki <> | Subject | Re: [PATCH 6/9] ksm: mem cgroup charge swapin copy |
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On Tue, 24 Nov 2009 16:51:13 +0000 (GMT) Hugh Dickins <hugh.dickins@tiscali.co.uk> wrote:
> But ksm swapping does require one small change in mem cgroup handling. > When do_swap_page()'s call to ksm_might_need_to_copy() does indeed > substitute a duplicate page to accommodate a different anon_vma (or a > different index), that page escaped mem cgroup accounting, because of > the !PageSwapCache check in mem_cgroup_try_charge_swapin(). > > That was returning success without charging, on the assumption that > pte_same() would fail after, which is not the case here. Originally I > proposed that success, so that an unshrinkable mem cgroup at its limit > would not fail unnecessarily; but that's a minor point, and there are > plenty of other places where we may fail an overallocation which might > later prove unnecessary. So just go ahead and do what all the other > exceptions do: proceed to charge current mm. > > Signed-off-by: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Ok. Maybe commit_charge will work enough. (I hope so.)
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
BTW, I'm happy if you adds "How to test" documenation to Documentation/vm/ksm.txt or to share some test programs.
1. Map anonymous pages + madvise(MADV_MERGEABLE) 2. "echo 1 > /sys/kernel/mm/ksm/run"
is enough ?
Thanks, -Kame
> --- > > mm/memcontrol.c | 7 ++++--- > 1 file changed, 4 insertions(+), 3 deletions(-) > > --- ksm5/mm/memcontrol.c 2009-11-14 10:17:02.000000000 +0000 > +++ ksm6/mm/memcontrol.c 2009-11-22 20:40:37.000000000 +0000 > @@ -1862,11 +1862,12 @@ int mem_cgroup_try_charge_swapin(struct > goto charge_cur_mm; > /* > * A racing thread's fault, or swapoff, may have already updated > - * the pte, and even removed page from swap cache: return success > - * to go on to do_swap_page()'s pte_same() test, which should fail. > + * the pte, and even removed page from swap cache: in those cases > + * do_swap_page()'s pte_same() test will fail; but there's also a > + * KSM case which does need to charge the page. > */ > if (!PageSwapCache(page)) > - return 0; > + goto charge_cur_mm; > mem = try_get_mem_cgroup_from_swapcache(page); > if (!mem) > goto charge_cur_mm; > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/
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