Messages in this thread | | | Date | Wed, 15 Jul 2009 20:21:14 -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 23:10:43 -0400 Rik van Riel <riel@redhat.com> wrote:
> Andrew Morton wrote: > > 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? > > It's been there for years, in various forms. It hardly ever > shows up, but Kosaki's patch series give us a nice chance to > fix it for good.
OK.
> >> @@ -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(). > > Good point, I should add some code to break out of page reclaim > if a fatal signal is pending,
We can't just return NULL from __alloc_pages(), and if we can't get a page from the freelists then we're just going to have to keep reclaiming. So I'm not sure how we can do this.
> and use a normal schedule_timeout > otherwise.
congestion_wait() would be typical.
> Btw, how is this laid out wrong? How do I do this better?
ask checkpatch ;)
WARNING: braces {} are not necessary for single statement blocks #99: FILE: mm/vmscan.c:1073: + while (unlikely(too_many_isolated(zone, file))) { + schedule_timeout_interruptible(HZ/10); + }
total: 0 errors, 1 warnings, 37 lines checked
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