linux-kernel - Re: Yet more softlockups.

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Date:	Wed, 10 Jul 2013 17:20:15 +0200
From:	Markus Trippelsdorf <markus@...ppelsdorf.de>
To:	Dave Jones <davej@...hat.com>, Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Peter Anvin <hpa@...or.com>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: Yet more softlockups.

On 2013.07.10 at 11:13 -0400, Dave Jones wrote:
> On Sat, Jul 06, 2013 at 09:24:08AM +0200, Ingo Molnar wrote:
>  > 
>  > * Dave Jones <davej@...hat.com> wrote:
>  > 
>  > > On Fri, Jul 05, 2013 at 05:15:07PM +0200, Thomas Gleixner wrote:
>  > >  > On Fri, 5 Jul 2013, Dave Jones wrote:
>  > >  > 
>  > >  > > BUG: soft lockup - CPU#3 stuck for 23s! [trinity-child1:14565]
>  > >  > > perf samples too long (2519 > 2500), lowering kernel.perf_event_max_sample_rate to 50000
>  > >  > > INFO: NMI handler (perf_event_nmi_handler) took too long to run: 238147.002 msecs
>  > >  > 
>  > >  > So we see a softlockup of 23 seconds and the perf_event_nmi_handler
>  > >  > claims it did run 23.8 seconds.
>  > >  > 
>  > >  > Are there more instances of NMI handler messages ?
>  > > 
>  > > [ 2552.006181] perf samples too long (2511 > 2500), lowering kernel.perf_event_max_sample_rate to 50000
>  > > [ 2552.008680] INFO: NMI handler (perf_event_nmi_handler) took too long to run: 500392.002 msecs
>  > 
>  > Dave, could you pull in the latest perf fixes at:
>  > 
>  >    git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git perf/urgent
>  > 
>  > In particular this:
>  > 
>  >   e5302920da9e perf: Fix interrupt handler timing harness
>  > 
>  > could make a difference - if your tests somehow end up activating perf.
> 
> Something is really fucked up in the kernel side of perf.
> I get this right after booting..
> 
> [  114.516619] perf samples too long (4262 > 2500), lowering kernel.perf_event_max_sample_rate to 50000

You can disable this warning by:

echo 0 > /proc/sys/kernel/perf_cpu_time_max_percent

-- 
Markus
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