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

From Tejun Heo <htejun@gmail.com>
Newsgroups linux.kernel
Subject Re: [PATCH] mm,vmscan: Use accurate values for zone_reclaimable() checks
Date 2015-10-23 20:30 +0200
Message-ID <qmPgf-112-39@gated-at.bofh.it> (permalink)
References (1 earlier) <qmt61-2wa-15@gated-at.bofh.it> <qmG3g-4qs-3@gated-at.bofh.it> <qmHVn-7dR-5@gated-at.bofh.it> <qmIy5-8dX-9@gated-at.bofh.it> <qmJDR-1jR-19@gated-at.bofh.it>
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Hello, Tetsuo.

On Fri, Oct 23, 2015 at 09:25:11PM +0900, Tetsuo Handa wrote:
> WQ_MEM_RECLAIM only guarantees that a "struct task_struct" is preallocated
> in order to avoid failing to allocate it on demand due to a GFP_KERNEL
> allocation? Is this correct?
> 
> WQ_CPU_INTENSIVE only guarantees that work items don't participate in
> concurrency management in order to avoid failing to wake up a "struct
> task_struct" which will process the work items? Is this correct?

CPU_INTENSIVE avoids the tail end of concurrency management.  The
previous HIGHPRI or the posted IMMEDIATE avoids the head end.

> Is Michal's question "does it make sense to use WQ_MEM_RECLAIM without
> WQ_CPU_INTENSIVE"? In other words, any "struct task_struct" which calls
> rescuer_thread() must imply WQ_CPU_INTENSIVE in order to avoid failing to
> wake up due to being participated in concurrency management?

If this is an actual problem, a better approach would be something
which detects the stall condition and kicks off the next work item but
if we do that I think I'd still trigger a warning there.  I don't
know.  Don't go busy waiting in kernel.

Thanks.

-- 
tejun
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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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