Re: [RFC 3/8] vmscan: make isolate_lru_page with filter aware

[Johannes Weiner <hannes@cmpxchg.org>]

On Wed, Apr 27, 2011 at 05:03:04PM +0900, KAMEZAWA Hiroyuki wrote:
> On Wed, 27 Apr 2011 01:25:20 +0900
> Minchan Kim <minchan.kim@gmail.com> wrote:
> 
> > In some __zone_reclaim case, we don't want to shrink mapped page.
> > Nonetheless, we have isolated mapped page and re-add it into
> > LRU's head. It's unnecessary CPU overhead and makes LRU churning.
> > 
> > Of course, when we isolate the page, the page might be mapped but
> > when we try to migrate the page, the page would be not mapped.
> > So it could be migrated. But race is rare and although it happens,
> > it's no big deal.
> > 
> > Cc: Christoph Lameter <cl@linux.com>
> > Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
> > Cc: Mel Gorman <mgorman@suse.de>
> > Cc: Rik van Riel <riel@redhat.com>
> > Cc: Andrea Arcangeli <aarcange@redhat.com>
> > Signed-off-by: Minchan Kim <minchan.kim@gmail.com>
> 
> 
> Hmm, it seems mm/memcontrol.c::mem_cgroup_isolate_pages() should be updated, too.

memcg reclaim always does sc->may_unmap = 1.  What is there to
communicate to mem_cgroup_isolate_pages?