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Re: [RFC][PATCH] dm: Remove dm_bufio_cond_resched()

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On Thu, Sep 22, 2016 at 10:59:30PM +0200, Thomas Gleixner wrote:
> On Thu, 22 Sep 2016, Mikulas Patocka wrote:
> > On Mon, 19 Sep 2016, Peter Zijlstra wrote:
> > 
> > > On Tue, Sep 13, 2016 at 09:39:59AM -0400, Mike Snitzer wrote:
> > > > So I'm not sure how this dm-bufio local cond_resched() wrapper still got
> > > > in... happy to take your patch.
> > > > 
> > > > Please respond with whatever SOB you'd like applied to the patch header.
> > > 
> > > Sorry, for the delay, here goes.
> > 
> > Why not change it to might_sleep()? - that would be almost equivalent to 
> 
> You mean might_resched(). might_sleep() is not even remotely equivalent.

It is, might_sleep() implies might_resched(). In fact, that's all what
PREEMPT_VOLUNTARY is, make the might_sleep() debug test imply a resched
point.

> > If we call the cond_resched() function in tight loops such as walking all 
> > buffers in a list, there may be performance penalty due to the call, so 
> > the call should be done only if it is really needed (i.e. in 
> > CONFIG_PREEMPT_VOLUNTARY case).
> 
> Makes sense.

Is anybody still using PREEMPT_NONE? Most workloads also care about
latency to some extend. Lots of code has explicit cond_resched() and
doesn't worry.

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[RFC][PATCH] dm: Remove dm_bufio_cond_resched() Peter Zijlstra <peterz@infradead.org> - 2016-09-13 10:50 +0200
  Re: [RFC][PATCH] dm: Remove dm_bufio_cond_resched() Thomas Gleixner <tglx@linutronix.de> - 2016-09-13 15:00 +0200
  Re: [RFC][PATCH] dm: Remove dm_bufio_cond_resched() Mike Snitzer <snitzer@redhat.com> - 2016-09-13 15:50 +0200
    Re: [RFC][PATCH] dm: Remove dm_bufio_cond_resched() Peter Zijlstra <peterz@infradead.org> - 2016-09-19 13:00 +0200
      Re: [RFC][PATCH] dm: Remove dm_bufio_cond_resched() Mikulas Patocka <mpatocka@redhat.com> - 2016-09-22 23:00 +0200
        Re: [RFC][PATCH] dm: Remove dm_bufio_cond_resched() Thomas Gleixner <tglx@linutronix.de> - 2016-09-22 23:10 +0200
          Re: [RFC][PATCH] dm: Remove dm_bufio_cond_resched() Peter Zijlstra <peterz@infradead.org> - 2016-09-23 09:40 +0200
            Re: [RFC][PATCH] dm: Remove dm_bufio_cond_resched() Thomas Gleixner <tglx@linutronix.de> - 2016-09-23 10:10 +0200
              Re: [RFC][PATCH] dm: Remove dm_bufio_cond_resched() Peter Zijlstra <peterz@infradead.org> - 2016-09-23 11:10 +0200
                Re: [RFC][PATCH] dm: Remove dm_bufio_cond_resched() Thomas Gleixner <tglx@linutronix.de> - 2016-09-23 11:20 +0200
                Re: [RFC][PATCH] dm: Remove dm_bufio_cond_resched() Ingo Molnar <mingo@kernel.org> - 2016-09-23 11:30 +0200
              Re: [RFC][PATCH] dm: Remove dm_bufio_cond_resched() Mike Galbraith <umgwanakikbuti@gmail.com> - 2016-09-23 14:20 +0200
                Re: [RFC][PATCH] dm: Remove dm_bufio_cond_resched() Peter Zijlstra <peterz@infradead.org> - 2016-09-23 14:30 +0200
                Re: [RFC][PATCH] dm: Remove dm_bufio_cond_resched() Mike Galbraith <umgwanakikbuti@gmail.com> - 2016-09-23 14:40 +0200
                Re: [RFC][PATCH] dm: Remove dm_bufio_cond_resched() Mike Snitzer <snitzer@redhat.com> - 2016-09-23 14:50 +0200
                Re: [RFC][PATCH] dm: Remove dm_bufio_cond_resched() Peter Zijlstra <peterz@infradead.org> - 2016-09-23 14:50 +0200
  Re: [RFC][PATCH] dm: Remove dm_bufio_cond_resched() Mikulas Patocka <mpatocka@redhat.com> - 2016-09-19 11:50 +0200
    Re: [RFC][PATCH] dm: Remove dm_bufio_cond_resched() Peter Zijlstra <peterz@infradead.org> - 2016-09-19 12:50 +0200

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