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Re: [RFC 2/3] mm: throttle on IO only when there are too many dirty and writeback pages

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On Fri 30-10-15 14:48:40, KAMEZAWA Hiroyuki wrote:
[...]
> > @@ -3191,8 +3191,23 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
> >   		 */
> >   		if (__zone_watermark_ok(zone, order, min_wmark_pages(zone),
> >   				ac->high_zoneidx, alloc_flags, target)) {
> > -			/* Wait for some write requests to complete then retry */
> > -			wait_iff_congested(zone, BLK_RW_ASYNC, HZ/50);
> > +			unsigned long writeback = zone_page_state(zone, NR_WRITEBACK),
> > +				      dirty = zone_page_state(zone, NR_FILE_DIRTY);
> > +
> > +			if (did_some_progress)
> > +				goto retry;
> > +
> > +			/*
> > +			 * If we didn't make any progress and have a lot of
> > +			 * dirty + writeback pages then we should wait for
> > +			 * an IO to complete to slow down the reclaim and
> > +			 * prevent from pre mature OOM
> > +			 */
> > +			if (2*(writeback + dirty) > reclaimable)
> 
> Doesn't this add unnecessary latency if other zones have enough clean memory ?

We know we haven't made any progress the last reclaim round so any zone
with a clean memory is rather unlikely.

-- 
Michal Hocko
SUSE Labs
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Thread

RFC: OOM detection rework v1 mhocko@kernel.org - 2015-10-29 16:20 +0100
  [RFC 3/3] mm: use watermak checks for __GFP_REPEAT high order allocations mhocko@kernel.org - 2015-10-29 16:20 +0100
  [RFC 1/3] mm, oom: refactor oom detection mhocko@kernel.org - 2015-10-29 16:20 +0100
    Re: [RFC 1/3] mm, oom: refactor oom detection "Hillf Danton" <hillf.zj@alibaba-inc.com> - 2015-10-30 05:20 +0100
      Re: [RFC 1/3] mm, oom: refactor oom detection Michal Hocko <mhocko@kernel.org> - 2015-10-30 09:40 +0100
        Re: [RFC 1/3] mm, oom: refactor oom detection Michal Hocko <mhocko@kernel.org> - 2015-10-30 11:20 +0100
          Re: [RFC 1/3] mm, oom: refactor oom detection Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2015-10-30 14:40 +0100
            Re: [RFC 1/3] mm, oom: refactor oom detection Michal Hocko <mhocko@kernel.org> - 2015-10-30 16:00 +0100
          Re: [RFC 1/3] mm, oom: refactor oom detection "Hillf Danton" <hillf.zj@alibaba-inc.com> - 2015-10-31 05:00 +0100
    Re: [RFC 1/3] mm, oom: refactor oom detection Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> - 2015-10-30 06:30 +0100
      Re: [RFC 1/3] mm, oom: refactor oom detection Michal Hocko <mhocko@kernel.org> - 2015-10-30 09:30 +0100
        Re: [RFC 1/3] mm, oom: refactor oom detection Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> - 2015-10-30 10:50 +0100
          Re: [RFC 1/3] mm, oom: refactor oom detection Michal Hocko <mhocko@kernel.org> - 2015-10-30 11:20 +0100
  [RFC 2/3] mm: throttle on IO only when there are too many dirty and writeback pages mhocko@kernel.org - 2015-10-29 16:20 +0100
    Re: [RFC 2/3] mm: throttle on IO only when there are too many dirty and writeback pages "Hillf Danton" <hillf.zj@alibaba-inc.com> - 2015-10-30 05:30 +0100
      Re: [RFC 2/3] mm: throttle on IO only when there are too many dirty  and writeback pages Michal Hocko <mhocko@kernel.org> - 2015-10-30 09:40 +0100
    Re: [RFC 2/3] mm: throttle on IO only when there are too many dirty  and writeback pages Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> - 2015-10-30 06:50 +0100
      Re: [RFC 2/3] mm: throttle on IO only when there are too many dirty  and writeback pages Michal Hocko <mhocko@kernel.org> - 2015-10-30 09:40 +0100

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