Messages in this thread | | | From | KOSAKI Motohiro <> | Date | Mon, 30 Apr 2012 16:32:40 -0400 | Subject | Re: [PATCH v3] proc: report file/anon bit in /proc/pid/pagemap |
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On Mon, Apr 30, 2012 at 6:48 AM, Konstantin Khlebnikov <khlebnikov@openvz.org> wrote: > This is an implementation of Andrew's proposal to extend the pagemap file > bits to report what is missing about tasks' working set. > > The problem with the working set detection is multilateral. In the criu > (checkpoint/restore) project we dump the tasks' memory into image files > and to do it properly we need to detect which pages inside mappings are > really in use. The mincore syscall I though could help with this did not. > First, it doesn't report swapped pages, thus we cannot find out which > parts of anonymous mappings to dump. Next, it does report pages from page > cache as present even if they are not mapped, and it doesn't make > difference between private pages that has been cow-ed and private pages > that has not been cow-ed. > > Note, that issue with swap pages is critical -- we must dump swap pages to > image file. But the issues with file pages are optimization -- we can take > all file pages to image, this would be correct, but if we know that a page > is not mapped or not cow-ed, we can remove them from dump file. The dump > would still be self-consistent, though significantly smaller in size (up > to 10 times smaller on real apps). > > Andrew noticed, that the proc pagemap file solved 2 of 3 above issues -- it > reports whether a page is present or swapped and it doesn't report not > mapped page cache pages. But, it doesn't distinguish cow-ed file pages from > not cow-ed. > > I would like to make the last unused bit in this file to report whether the > page mapped into respective pte is PageAnon or not. > > [comment stolen from Pavel Emelyanov's v1 patch] > > v2: > * Rebase to uptodate kernel > * Fix file/anon bit reporting for migration entries > * Fix frame bits interval comment, it uses 55 lower bits (64 - 3 - 6) > > v3: > * fix stupid misprint s/if/else if/ > * rebase on top of "[PATCH bugfix] proc/pagemap: correctly report non-present > ptes and holes between vmas" > * second patch (with indexes for nonlinear mappings) was droppped. > > Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org> > Cc: Pavel Emelyanov <xemul@parallels.com> > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: Matt Mackall <mpm@selenic.com> > Cc: Hugh Dickins <hughd@google.com> > Cc: Rik van Riel <riel@redhat.com> > Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
I don't like an exporting naive kernel internal. But unfortunately I have no alternative idea.. Acked-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> -- 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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