Re: [PATCH 16/34] mm: compaction: Allow compaction to isolate dirty pages

Mel Gorman
2012-07-25T16:07:54Z

On Wed, Jul 25, 2012 at 08:47:45AM -0700, Greg KH wrote:
> On Mon, Jul 23, 2012 at 02:38:29PM +0100, Mel Gorman wrote:
> > commit a77ebd333cd810d7b680d544be88c875131c2bd3 upstream.
> >
> > Stable note: Not tracked in Bugzilla. A fix aimed at preserving page aging
> > information by reducing LRU list churning had the side-effect of
> > reducing THP allocation success rates. This was part of a series
> > to restore the success rates while preserving the reclaim fix.
> >
> > Commit [39deaf85: mm: compaction: make isolate_lru_page() filter-aware]
> > noted that compaction does not migrate dirty or writeback pages and
> > that is was meaningless to pick the page and re-add it to the LRU list.
> >
> > What was missed during review is that asynchronous migration moves
> > dirty pages if their ->migratepage callback is migrate_page() because
> > these can be moved without blocking. This potentially impacted
> > hugepage allocation success rates by a factor depending on how many
> > dirty pages are in the system.
> >
> > This patch partially reverts 39deaf85 to allow migration to isolate
> > dirty pages again. This increases how much compaction disrupts the
> > LRU but that is addressed later in the series.
> >
> > Signed-off-by: Mel Gorman <mgorman@suse.de>
> > Reviewed-by: Andrea Arcangeli <aarcange@redhat.com>
> > Reviewed-by: Rik van Riel <riel@redhat.com>
> > Reviewed-by: Minchan Kim <minchan.kim@gmail.com>
>
> Note, the changelog here differs from what is in Linus's tree by a LOT.
> I took the version in Linus's tree instead.
>

Yet another case of where the distribution kernel got the patch first
and I mucked up the transfer back. In this case the mainline changelog
includes the patch leader with a lot of additional information.

--
Mel Gorman
SUSE Labs