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Re: [PATCH] workqueue: warn if memory reclaim tries to flush !WQ_MEM_RECLAIM workqueue

From Tejun Heo <tj@kernel.org>
Newsgroups linux.kernel
Subject Re: [PATCH] workqueue: warn if memory reclaim tries to flush !WQ_MEM_RECLAIM workqueue
Date 2015-12-03 22:00 +0100
Message-ID <qBJ8T-1Cs-61@gated-at.bofh.it> (permalink)
References (3 earlier) <qBDmN-6pd-21@gated-at.bofh.it> <qBDGa-6Nq-19@gated-at.bofh.it> <qBDGa-6Nq-17@gated-at.bofh.it> <qBHJL-QO-1@gated-at.bofh.it> <qBIZb-1y2-5@gated-at.bofh.it>
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Hey, Peter.

On Thu, Dec 03, 2015 at 09:43:13PM +0100, Peter Zijlstra wrote:
> I'm not sure about using PF_MEMALLOC for detecting reclaim. There appear
> to be more sites setting this than reclaim. See:
>
> drivers/block/nbd.c:	current->flags |= PF_MEMALLOC;
> drivers/mmc/card/queue.c:	current->flags |= PF_MEMALLOC;
> drivers/mtd/nand/nandsim.c:	current->flags |= PF_MEMALLOC;
> drivers/scsi/iscsi_tcp.c:	current->flags |= PF_MEMALLOC;
> drivers/staging/lustre/include/linux/libcfs/linux/linux-mem.h:#define memory_pressure_set() do { current->flags |= PF_MEMALLOC; } while (0)
> fs/cifs/connect.c:	current->flags |= PF_MEMALLOC;
> fs/xfs/libxfs/xfs_btree.c:		new_pflags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
> fs/xfs/xfs_trans_ail.c:	current->flags |= PF_MEMALLOC;
> include/linux/sched.h:	current->flags |= PF_MEMALLOC_NOIO;
> mm/page_alloc.c:	current->flags |= PF_MEMALLOC;
> mm/page_alloc.c:	current->flags |= PF_MEMALLOC;
> mm/vmscan.c:	tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
> mm/vmscan.c:	p->flags |= PF_MEMALLOC;
> mm/vmscan.c:	p->flags |= PF_MEMALLOC | PF_SWAPWRITE;
> net/core/dev.c:		current->flags |= PF_MEMALLOC;
> net/core/sock.c:	current->flags |= PF_MEMALLOC;
> 
> 
> The actual reclaim sites in page_alloc and vmscan set
> current->reclaim_state. So testing against that might be more accurate.

So, if I'm not mistaken, those are all marking tasks which can be
depended upon during memory reclaim and we do want to catch them all.
PF_MEMALLOC shouldn't depend on something which require memory to be
reclaimed to guarantee forward progress.

Thanks.

-- 
tejun
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Thread

[PATCH 1/2] watchdog: introduce touch_softlockup_watchdog_sched() Tejun Heo <tj@kernel.org> - 2015-12-03 01:30 +0100
  [PATCH 2/2] workqueue: implement lockup detector Tejun Heo <tj@kernel.org> - 2015-12-03 01:30 +0100
    Re: [PATCH 2/2] workqueue: implement lockup detector Tejun Heo <tj@kernel.org> - 2015-12-03 15:50 +0100
    Re: [PATCH 2/2] workqueue: implement lockup detector Don Zickus <dzickus@redhat.com> - 2015-12-03 19:00 +0100
      Re: [PATCH 2/2] workqueue: implement lockup detector Tejun Heo <tj@kernel.org> - 2015-12-03 20:50 +0100
        Re: [PATCH 2/2] workqueue: implement lockup detector Ulrich Obergfell <uobergfe@redhat.com> - 2015-12-03 21:20 +0100
          Re: [PATCH 2/2] workqueue: implement lockup detector Tejun Heo <tj@kernel.org> - 2015-12-03 22:00 +0100
            Re: [PATCH 2/2] workqueue: implement lockup detector Ingo Molnar <mingo@kernel.org> - 2015-12-04 09:10 +0100
              Re: [PATCH 2/2] workqueue: implement lockup detector Don Zickus <dzickus@redhat.com> - 2015-12-04 18:00 +0100
            Re: [PATCH 2/2] workqueue: implement lockup detector Ulrich Obergfell <uobergfe@redhat.com> - 2015-12-04 14:30 +0100
    [PATCH v2 2/2] workqueue: implement lockup detector Tejun Heo <tj@kernel.org> - 2015-12-07 20:10 +0100
      Re: [PATCH v2 2/2] workqueue: implement lockup detector Tejun Heo <tj@kernel.org> - 2015-12-07 22:40 +0100
        Re: [PATCH v2 2/2] workqueue: implement lockup detector Don Zickus <dzickus@redhat.com> - 2015-12-08 17:10 +0100
          Re: [PATCH v2 2/2] workqueue: implement lockup detector Tejun Heo <tj@kernel.org> - 2015-12-08 17:40 +0100
      Re: [PATCH v2 2/2] workqueue: implement lockup detector Don Zickus <dzickus@redhat.com> - 2015-12-07 22:40 +0100
  Re: [PATCH 1/2] watchdog: introduce touch_softlockup_watchdog_sched() Peter Zijlstra <peterz@infradead.org> - 2015-12-03 10:40 +0100
    Re: [PATCH 1/2] watchdog: introduce touch_softlockup_watchdog_sched() Peter Zijlstra <peterz@infradead.org> - 2015-12-03 11:10 +0100
      Re: [PATCH 1/2] watchdog: introduce touch_softlockup_watchdog_sched() Tejun Heo <tj@kernel.org> - 2015-12-03 15:50 +0100
        Re: [PATCH 1/2] watchdog: introduce touch_softlockup_watchdog_sched() Tejun Heo <tj@kernel.org> - 2015-12-03 16:10 +0100
          [PATCH] workqueue: warn if memory reclaim tries to flush  !WQ_MEM_RECLAIM workqueue Tejun Heo <tj@kernel.org> - 2015-12-03 20:30 +0100
            Re: [PATCH] workqueue: warn if memory reclaim tries to flush  !WQ_MEM_RECLAIM workqueue Peter Zijlstra <peterz@infradead.org> - 2015-12-03 21:50 +0100
              Re: [PATCH] workqueue: warn if memory reclaim tries to flush  !WQ_MEM_RECLAIM workqueue Tejun Heo <tj@kernel.org> - 2015-12-03 22:00 +0100
                Re: [PATCH] workqueue: warn if memory reclaim tries to flush  !WQ_MEM_RECLAIM workqueue Peter Zijlstra <peterz@infradead.org> - 2015-12-03 22:10 +0100
                Re: [PATCH] workqueue: warn if memory reclaim tries to flush  !WQ_MEM_RECLAIM workqueue Tejun Heo <tj@kernel.org> - 2015-12-03 23:10 +0100
                Re: [PATCH] workqueue: warn if memory reclaim tries to flush  !WQ_MEM_RECLAIM workqueue Peter Zijlstra <peterz@infradead.org> - 2015-12-04 14:00 +0100
            Re: [PATCH] workqueue: warn if memory reclaim tries to flush  !WQ_MEM_RECLAIM workqueue Tejun Heo <tj@kernel.org> - 2015-12-07 17:00 +0100
        Re: [PATCH 1/2] watchdog: introduce touch_softlockup_watchdog_sched() Peter Zijlstra <peterz@infradead.org> - 2015-12-03 16:10 +0100

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