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Re: [PATCH] mm,vmscan: Use accurate values for zone_reclaimable() checks

From Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Newsgroups linux.kernel
Subject Re: [PATCH] mm,vmscan: Use accurate values for zone_reclaimable() checks
Date 2015-10-21 17:40 +0200
Message-ID <qm3EB-7ex-13@gated-at.bofh.it> (permalink)
References <qm0GK-2RY-1@gated-at.bofh.it> <qm2yU-5Ck-51@gated-at.bofh.it> <qm2Iy-5OI-15@gated-at.bofh.it> <qm2Se-606-31@gated-at.bofh.it> <qm31U-6dh-27@gated-at.bofh.it>
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Michal Hocko wrote:
> On Wed 21-10-15 09:49:07, Christoph Lameter wrote:
> > On Wed, 21 Oct 2015, Michal Hocko wrote:
> > 
> > > Because all the WQ workers are stuck somewhere, maybe in the memory
> > > allocation which cannot make any progress and the vmstat update work is
> > > queued behind them.

After invoking the OOM killer, we can easily observe that vmstat_update
cannot be processed due to memory allocation by disk_events_workfn stalls.
http://lkml.kernel.org/r/201509120019.BJI48986.OOSVMJtOLFQHFF@I-love.SAKURA.ne.jp

I worried that blocking forever from workqueue is an exclusive occupation of
workqueue. In fact, changing to GFP_ATOMIC avoids this problem.
http://lkml.kernel.org/r/201503012017.EAD00571.HOOJVOStMFLFQF@I-love.SAKURA.ne.jp

Now we realized that we are hitting this problem before invoking the OOM
killer. The situation is similar to the case after the OOM killer is
invoked; there are no reclaimable pages but vmstat_update cannot be
processed. We are caught by a small difference of vmstat counter values.

> > >
> > > At least this is my current understanding.
> > 
> > Eww. Maybe need a queue that does not do such evil things as memory
> > allocation?
> 
> I am not sure how to achieve that. Requiring non-sleeping worker would
> work out but do we have enough users to add such an API?

If a queue does not need to sleep, can't that queue be processed from
timer context (e.g. mod_timer()) ?
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[PATCH] mm,vmscan: Use accurate values for zone_reclaimable() checks Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2015-10-21 14:30 +0200
  Re: [PATCH] mm,vmscan: Use accurate values for zone_reclaimable()  checks Michal Hocko <mhocko@kernel.org> - 2015-10-21 15:10 +0200
  Re: [PATCH] mm,vmscan: Use accurate values for zone_reclaimable()  checks Christoph Lameter <cl@linux.com> - 2015-10-21 16:30 +0200
    Re: [PATCH] mm,vmscan: Use accurate values for zone_reclaimable()  checks Michal Hocko <mhocko@kernel.org> - 2015-10-21 16:40 +0200
      Re: [PATCH] mm,vmscan: Use accurate values for zone_reclaimable()  checks Christoph Lameter <cl@linux.com> - 2015-10-21 16:50 +0200
        Re: [PATCH] mm,vmscan: Use accurate values for zone_reclaimable()  checks Michal Hocko <mhocko@kernel.org> - 2015-10-21 17:00 +0200
          Re: [PATCH] mm,vmscan: Use accurate values for zone_reclaimable() checks Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2015-10-21 17:40 +0200
          Re: [PATCH] mm,vmscan: Use accurate values for zone_reclaimable()  checks Christoph Lameter <cl@linux.com> - 2015-10-21 19:20 +0200
            Re: [PATCH] mm,vmscan: Use accurate values for zone_reclaimable() checks Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2015-10-22 13:40 +0200
              Re: [PATCH] mm,vmscan: Use accurate values for zone_reclaimable()  checks Christoph Lameter <cl@linux.com> - 2015-10-22 15:40 +0200
                Re: [PATCH] mm,vmscan: Use accurate values for zone_reclaimable()  checks Tejun Heo <htejun@gmail.com> - 2015-10-22 16:20 +0200
                Re: [PATCH] mm,vmscan: Use accurate values for zone_reclaimable()  checks Tejun Heo <htejun@gmail.com> - 2015-10-22 16:30 +0200
                Re: [PATCH] mm,vmscan: Use accurate values for zone_reclaimable()  checks Tejun Heo <htejun@gmail.com> - 2015-10-22 16:30 +0200
                Re: [PATCH] mm,vmscan: Use accurate values for zone_reclaimable()  checks Christoph Lameter <cl@linux.com> - 2015-10-22 16:30 +0200
                Re: [PATCH] mm,vmscan: Use accurate values for zone_reclaimable()  checks Tejun Heo <htejun@gmail.com> - 2015-10-22 16:40 +0200
                Re: [PATCH] mm,vmscan: Use accurate values for zone_reclaimable()  checks Christoph Lameter <cl@linux.com> - 2015-10-22 16:50 +0200
                Re: [PATCH] mm,vmscan: Use accurate values for zone_reclaimable()  checks Tejun Heo <htejun@gmail.com> - 2015-10-22 17:20 +0200
                Re: [PATCH] mm,vmscan: Use accurate values for zone_reclaimable()  checks Tejun Heo <htejun@gmail.com> - 2015-10-23 06:30 +0200
                Re: [PATCH] mm,vmscan: Use accurate values for zone_reclaimable()  checks Christoph Lameter <cl@linux.com> - 2015-10-22 16:30 +0200
                Re: [PATCH] mm,vmscan: Use accurate values for zone_reclaimable()  checks Christoph Lameter <cl@linux.com> - 2015-10-22 16:30 +0200
                Re: [PATCH] mm,vmscan: Use accurate values for zone_reclaimable()  checks Michal Hocko <mhocko@kernel.org> - 2015-10-22 17:10 +0200
                Re: [PATCH] mm,vmscan: Use accurate values for zone_reclaimable()  checks Tejun Heo <htejun@gmail.com> - 2015-10-22 17:20 +0200
                Re: [PATCH] mm,vmscan: Use accurate values for zone_reclaimable()  checks Christoph Lameter <cl@linux.com> - 2015-10-22 17:40 +0200
                Re: [PATCH] mm,vmscan: Use accurate values for zone_reclaimable()  checks Michal Hocko <mhocko@kernel.org> - 2015-10-23 10:40 +0200
                Make vmstat deferrable again (was Re: [PATCH] mm,vmscan: Use accurate  values for zone_reclaimable() checks) Christoph Lameter <cl@linux.com> - 2015-10-23 13:50 +0200
                Re: Make vmstat deferrable again (was Re: [PATCH] mm,vmscan: Use  accurate values for zone_reclaimable() checks) Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2015-10-23 14:10 +0200
                Re: Make vmstat deferrable again (was Re: [PATCH] mm,vmscan: Use  accurate values for zone_reclaimable() checks) Christoph Lameter <cl@linux.com> - 2015-10-23 16:20 +0200
                Re: Make vmstat deferrable again (was Re: [PATCH] mm,vmscan: Use  accurate values for zone_reclaimable() checks) Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2015-10-23 17:00 +0200
                Re: Make vmstat deferrable again (was Re: [PATCH] mm,vmscan: Use  accurate values for zone_reclaimable() checks) Christoph Lameter <cl@linux.com> - 2015-10-23 18:20 +0200
                Re: [PATCH] mm,vmscan: Use accurate values for zone_reclaimable()  checks Tejun Heo <htejun@gmail.com> - 2015-10-22 17:40 +0200
                Re: [PATCH] mm,vmscan: Use accurate values for zone_reclaimable()  checks Michal Hocko <mhocko@kernel.org> - 2015-10-22 17:50 +0200
                Re: [PATCH] mm,vmscan: Use accurate values for zone_reclaimable()  checks Tejun Heo <htejun@gmail.com> - 2015-10-22 20:50 +0200
                Re: [PATCH] mm,vmscan: Use accurate values for zone_reclaimable()checks Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2015-10-22 23:50 +0200
                Re: [PATCH] mm,vmscan: Use accurate values for  zone_reclaimable()checks Tejun Heo <htejun@gmail.com> - 2015-10-23 00:50 +0200
                Re: [PATCH] mm,vmscan: Use accurate values for  zone_reclaimable()checks Michal Hocko <mhocko@kernel.org> - 2015-10-23 10:40 +0200
                Re: [PATCH] mm,vmscan: Use accurate values for  zone_reclaimable()checks Tejun Heo <htejun@gmail.com> - 2015-10-23 12:40 +0200
                Re: [PATCH] mm,vmscan: Use accurate values for zone_reclaimable()  checks Michal Hocko <mhocko@kernel.org> - 2015-10-23 10:40 +0200
                Re: [PATCH] mm,vmscan: Use accurate values for zone_reclaimable()  checks Tejun Heo <htejun@gmail.com> - 2015-10-23 12:40 +0200
                Re: [PATCH] mm,vmscan: Use accurate values for zone_reclaimable()  checks Michal Hocko <mhocko@kernel.org> - 2015-10-23 13:20 +0200
                Re: [PATCH] mm,vmscan: Use accurate values for zone_reclaimable() checks Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2015-10-23 14:30 +0200
                Re: [PATCH] mm,vmscan: Use accurate values for zone_reclaimable()  checks Tejun Heo <htejun@gmail.com> - 2015-10-23 20:30 +0200
                Re: [PATCH] mm,vmscan: Use accurate values for zone_reclaimable() checks Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2015-10-25 12:00 +0100
                Re: [PATCH] mm,vmscan: Use accurate values for zone_reclaimable()  checks Tejun Heo <htejun@gmail.com> - 2015-10-25 23:50 +0100
                Re: [PATCH] mm,vmscan: Use accurate values for zone_reclaimable()  checks Michal Hocko <mhocko@kernel.org> - 2015-10-27 10:30 +0100
                Re: [PATCH] mm,vmscan: Use accurate values for zone_reclaimable()  checks Tejun Heo <htejun@gmail.com> - 2015-10-27 12:00 +0100
                Re: [PATCH] mm,vmscan: Use accurate values for zone_reclaimable()  checks Michal Hocko <mhocko@kernel.org> - 2015-10-27 13:10 +0100
                Re: [PATCH] mm,vmscan: Use accurate values for zone_reclaimable()  checks Tejun Heo <htejun@gmail.com> - 2015-10-23 20:30 +0200
                Re: [PATCH] mm,vmscan: Use accurate values for zone_reclaimable()  checks Michal Hocko <mhocko@kernel.org> - 2015-10-27 10:20 +0100
                Re: [PATCH] mm,vmscan: Use accurate values for zone_reclaimable()  checks Tejun Heo <htejun@gmail.com> - 2015-10-27 12:00 +0100
                Re: [PATCH] mm,vmscan: Use accurate values for zone_reclaimable()checks Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2015-10-27 12:10 +0100
                Re: [PATCH] mm,vmscan: Use accurate values for  zone_reclaimable()checks Tejun Heo <htejun@gmail.com> - 2015-10-27 12:40 +0100
                Re: [PATCH] mm,vmscan: Use accurate values for zone_reclaimable()  checks Michal Hocko <mhocko@kernel.org> - 2015-10-22 17:40 +0200

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