From: Peter Zijlstra <peterz@infradead.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Mikulas Patocka <mpatocka@redhat.com>,
Mike Snitzer <snitzer@redhat.com>,
Alasdair Kergon <agk@redhat.com>, Ingo Molnar <mingo@kernel.org>,
linux-kernel@vger.kernel.org, dm-devel@redhat.com,
Joe Thornber <ejt@redhat.com>
Subject: Re: [RFC][PATCH] dm: Remove dm_bufio_cond_resched()
Date: Fri, 23 Sep 2016 09:34:35 +0200 [thread overview]
Message-ID: <20160923073435.GL2794@worktop> (raw)
In-Reply-To: <alpine.DEB.2.20.1609222257050.5640@nanos>
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.
next prev parent reply other threads:[~2016-09-23 7:34 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-13 8:45 [RFC][PATCH] dm: Remove dm_bufio_cond_resched() Peter Zijlstra
2016-09-13 12:49 ` Thomas Gleixner
2016-09-13 13:39 ` Mike Snitzer
2016-09-19 10:53 ` Peter Zijlstra
2016-09-22 20:53 ` Mikulas Patocka
2016-09-22 20:59 ` Thomas Gleixner
2016-09-23 7:34 ` Peter Zijlstra [this message]
2016-09-23 8:00 ` Thomas Gleixner
2016-09-23 9:05 ` Peter Zijlstra
2016-09-23 9:13 ` Thomas Gleixner
2016-09-23 9:26 ` Ingo Molnar
2016-09-23 12:17 ` Mike Galbraith
2016-09-23 12:26 ` Peter Zijlstra
2016-09-23 12:39 ` Mike Galbraith
2016-09-23 12:42 ` Mike Snitzer
2016-09-23 12:46 ` Peter Zijlstra
2016-09-23 14:32 ` [dm-devel] " Bart Van Assche
2016-09-23 14:32 ` Bart Van Assche
2016-09-19 9:49 ` Mikulas Patocka
2016-09-19 10:47 ` Peter Zijlstra
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