On 04/27/2012 04:39 PM, Konstantin Khlebnikov 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. > > 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) > > Signed-off-by: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxx> > Cc: Pavel Emelyanov <xemul@xxxxxxxxxxxxx> > Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > Cc: Hugh Dickins <hughd@xxxxxxxxxx> > Cc: Rik van Riel <riel@xxxxxxxxxx> Acked-by: Pavel Emelyanov <xemul@xxxxxxxxxxxxx> -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>