Messages in this thread | | | Date | Wed, 15 Jul 2009 19:48:20 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH -mm] throttle direct reclaim when too many pages are isolated already |
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On Wed, 15 Jul 2009 22:38:53 -0400 Rik van Riel <riel@redhat.com> wrote:
> When way too many processes go into direct reclaim, it is possible > for all of the pages to be taken off the LRU. One result of this > is that the next process in the page reclaim code thinks there are > no reclaimable pages left and triggers an out of memory kill. > > One solution to this problem is to never let so many processes into > the page reclaim path that the entire LRU is emptied. Limiting the > system to only having half of each inactive list isolated for > reclaim should be safe. >
Since when? Linux page reclaim has a bilion machine years testing and now stuff like this turns up. Did we break it or is this a never-before-discovered workload?
> --- > This patch goes on top of Kosaki's "Account the number of isolated pages" > patch series. > > mm/vmscan.c | 25 +++++++++++++++++++++++++ > 1 file changed, 25 insertions(+) > > Index: mmotm/mm/vmscan.c > =================================================================== > --- mmotm.orig/mm/vmscan.c 2009-07-08 21:37:01.000000000 -0400 > +++ mmotm/mm/vmscan.c 2009-07-08 21:39:02.000000000 -0400 > @@ -1035,6 +1035,27 @@ int isolate_lru_page(struct page *page) > } > > /* > + * Are there way too many processes in the direct reclaim path already? > + */ > +static int too_many_isolated(struct zone *zone, int file) > +{ > + unsigned long inactive, isolated; > + > + if (current_is_kswapd()) > + return 0; > + > + if (file) { > + inactive = zone_page_state(zone, NR_INACTIVE_FILE); > + isolated = zone_page_state(zone, NR_ISOLATED_FILE); > + } else { > + inactive = zone_page_state(zone, NR_INACTIVE_ANON); > + isolated = zone_page_state(zone, NR_ISOLATED_ANON); > + } > + > + return isolated > inactive; > +} > + > +/* > * shrink_inactive_list() is a helper for shrink_zone(). It returns the number > * of reclaimed pages > */ > @@ -1049,6 +1070,10 @@ static unsigned long shrink_inactive_lis > struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc); > int lumpy_reclaim = 0; > > + while (unlikely(too_many_isolated(zone, file))) { > + schedule_timeout_interruptible(HZ/10); > + }
This (incorrectly-laid-out) code is a no-op if signal_pending().
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