Messages in this thread | | | Date | Wed, 15 Jul 2009 20:38:54 -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 23:28:14 -0400 Rik van Riel <riel@redhat.com> wrote:
> Andrew Morton wrote: > > 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. > > If we are stuck at this point in the page reclaim code, > it is because too many other tasks are reclaiming pages. > > That makes it fairly safe to just return SWAP_CLUSTER_MAX > here and hope that __alloc_pages() can get a page. > > After all, if __alloc_pages() thinks it made progress, > but still cannot make the allocation, it will call the > pageout code again.
Which will immediately return because the caller still has fatal_signal_pending()?
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