linux-kernel - Re: [tip:sched/core] sched: Add NEED_RESCHED to the preempt

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Message-ID: <20130927122015.GA20270@localhost>
Date:	Fri, 27 Sep 2013 20:20:15 +0800
From:	Fengguang Wu <fengguang.wu@...el.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Yuanhan Liu <yuanhan.liu@...ux.intel.com>, mingo@...nel.org,
	hpa@...or.com, linux-kernel@...r.kernel.org, tglx@...utronix.de,
	linux-tip-commits@...r.kernel.org,
	Huang Ying <ying.huang@...el.com>, lkp@...ux.intel.com
Subject: Re: [tip:sched/core] sched: Add NEED_RESCHED to the preempt_count

On Fri, Sep 27, 2013 at 08:13:11PM +0800, Fengguang Wu wrote:
> On Fri, Sep 27, 2013 at 01:57:22PM +0200, Peter Zijlstra wrote:
> > On Fri, Sep 27, 2013 at 05:14:27PM +0800, Yuanhan Liu wrote:
> > > On Wed, Sep 25, 2013 at 09:38:38AM -0700, tip-bot for Peter Zijlstra wrote:
> > > > Commit-ID:  f27dde8deef33c9e58027df11ceab2198601d6a6
> > > > Gitweb:     http://git.kernel.org/tip/f27dde8deef33c9e58027df11ceab2198601d6a6
> > > > Author:     Peter Zijlstra <peterz@...radead.org>
> > > > AuthorDate: Wed, 14 Aug 2013 14:55:31 +0200
> > > > Committer:  Ingo Molnar <mingo@...nel.org>
> > > > CommitDate: Wed, 25 Sep 2013 14:07:49 +0200
> > > > 
> > > > sched: Add NEED_RESCHED to the preempt_count
> > > 
> > > Hi Peter,
> > > 
> > > FYI, here we found a pigz regression by this commit.
> > 
> > I just can't help myself; but pigs aren't supposed to fly anyway! :-)
> 
> Aha!

> > > Here is a list all of changed stats by this commit and it's parent 4a2b4b222743bb07fedf985b884550f2ca067ea9:
> > > 
> > > time.involuntary_context_switches                                          [ 3184       - 4753       ]     [ 5.536e+05  - 5.9042e+05 ]
> > > time.voluntary_context_switches                                            [ 84559      - 1.2223e+05 ]     [ 1.1008e+07 - 1.1092e+07 ]
> > 
> > Gah, that looks like it completely wrecked preemptions.

> > What kind of PREEMPT Kconfig options do you use? Or rather; could you
> > attach your .config?
> 
> Attached.

Sorry it's this one.

Thanks,
Fengguang

View attachment "config-3.12.0-rc1-00055-gf27dde8" of type "text/plain" (80037 bytes)