Re: [RFC][PATCH v2 1/2] printk: Make printk() completely async

From	Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Newsgroups	linux.kernel
Subject	Re: [RFC][PATCH v2 1/2] printk: Make printk() completely async
Date	2016-03-07 15:40 +0100
Message-ID	<ra4ug-42s-73@gated-at.bofh.it> (permalink)
References	(1 earlier) <r9EJr-4dl-1@gated-at.bofh.it> <r9GUW-5zH-5@gated-at.bofh.it> <r9YI9-oh-5@gated-at.bofh.it> <ra0qC-1wR-25@gated-at.bofh.it> <ra1mG-27y-13@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On (03/07/16 20:10), Tetsuo Handa wrote:
[..]
> > > > hm. yes, seems that it may take some time until workqueue wakeup() a ->rescuer thread.
> > > > need to look more.
> > > 
> > > Yes, it takes some time (0.1s or 2 jiffies) before workqueue code gives up
> > > creating a worker process and wakes up rescuer thread. However I don't see
> > > that as a problem...
> > 
> > yes, that's why I asked Tetsuo whether his concern was a wq's MAYDAY timer
> > delay. the two commits that Tetsuo pointed at earlier in he loop (373ccbe59270
> > and 564e81a57f97) solved the problem by switching to WQ_MEM_RECLAIM wq.
> > I've slightly tested OOM-kill on my desktop system and haven't spotted any
> > printk delays (well, a test on desktop is not really representative, of
> > course).
> 
> I wanted to tell that if kworker is running a buggy function that calls
> cond_resched() but does not call schedule_timeout_*() for very long time,
> such delay can become many seconds. WQ_MEM_RECLAIM is a requirement for
> waking up when kworker called schedule_timeout_*(). WQ_MEM_RECLAIM wq can
> still cause huge delay if kworker does not call schedule_timeout_*().
> Not specific to OOM-killer or vmstat.

your point is taken. thanks.

	-ss

Thread

[RFC][PATCH v2 1/2] printk: Make printk() completely async Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2016-03-05 12:00 +0100
  Re: [RFC][PATCH v2 1/2] printk: Make printk() completely async Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2016-03-06 07:40 +0100
    Re: [RFC][PATCH v2 1/2] printk: Make printk() completely async Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2016-03-06 08:20 +0100
      Re: [RFC][PATCH v2 1/2] printk: Make printk() completely async Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2016-03-06 10:40 +0100
        Re: [RFC][PATCH v2 1/2] printk: Make printk() completely async Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2016-03-06 12:10 +0100
          Re: [RFC][PATCH v2 1/2] printk: Make printk() completely async Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2016-03-06 14:30 +0100
            Re: [RFC][PATCH v2 1/2] printk: Make printk() completely async Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2016-03-06 16:00 +0100
            Re: [RFC][PATCH v2 1/2] printk: Make printk() completely async Jan Kara <jack@suse.cz> - 2016-03-07 09:30 +0100
              Re: [RFC][PATCH v2 1/2] printk: Make printk() completely async Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2016-03-07 11:20 +0100
                Re: [RFC][PATCH v2 1/2] printk: Make printk() completely async Jan Kara <jack@suse.cz> - 2016-03-07 12:00 +0100
                Re: [RFC][PATCH v2 1/2] printk: Make printk() completely async Jan Kara <jack@suse.cz> - 2016-03-07 13:20 +0100
                Re: [RFC][PATCH v2 1/2] printk: Make printk() completely async Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2016-03-07 13:40 +0100
                Re: [RFC][PATCH v2 1/2] printk: Make printk() completely async Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2016-03-07 16:20 +0100
                Re: [RFC][PATCH v2 1/2] printk: Make printk() completely async Tejun Heo <tj@kernel.org> - 2016-03-07 17:00 +0100
                Re: [RFC][PATCH v2 1/2] printk: Make printk() completely async Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2016-03-08 11:30 +0100
                Re: [RFC][PATCH v2 1/2] printk: Make printk() completely async Tejun Heo <tj@kernel.org> - 2016-03-11 18:30 +0100
                Re: [RFC][PATCH v2 1/2] printk: Make printk() completely async Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2016-03-12 06:10 +0100
                Re: [RFC][PATCH v2 1/2] printk: Make printk() completely async Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2016-03-09 07:10 +0100
                Re: [RFC][PATCH v2 1/2] printk: Make printk() completely async Jan Kara <jack@suse.cz> - 2016-03-10 10:30 +0100
                Re: [RFC][PATCH v2 1/2] printk: Make printk() completely async Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2016-03-10 17:00 +0100
                Re: [RFC][PATCH v2 1/2] printk: Make printk() completely async Petr Mladek <pmladek@suse.com> - 2016-03-10 11:00 +0100
                Re: [RFC][PATCH v2 1/2] printk: Make printk() completely async Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2016-03-10 17:30 +0100
                Re: [RFC][PATCH v2 1/2] printk: Make printk() completely async Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2016-03-07 15:50 +0100
                Re: [RFC][PATCH v2 1/2] printk: Make printk() completely async Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2016-03-07 12:20 +0100
                Re: [RFC][PATCH v2 1/2] printk: Make printk() completely async Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2016-03-07 15:40 +0100
              Re: [RFC][PATCH v2 1/2] printk: Make printk() completely async Tejun Heo <tj@kernel.org> - 2016-03-07 16:50 +0100

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