linux-kernel - Re: Yet more softlockups.

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Date:	Fri, 12 Jul 2013 11:12:13 -0600
From:	David Ahern <dsahern@...il.com>
To:	Dave Jones <davej@...hat.com>, Dave Hansen <dave.hansen@...el.com>,
	Ingo Molnar <mingo@...nel.org>,
	Markus Trippelsdorf <markus@...ppelsdorf.de>,
	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>,
	Dave Hansen <dave.hansen@...ux.intel.com>
Subject: Re: Yet more softlockups.

On 7/12/13 9:45 AM, Dave Jones wrote:
> Here's a fun trick:
>
> trinity -c perf_event_open -C4 -q -l off
>
> Within about a minute, that brings any of my boxes to its knees.
> The softlockup detector starts going nuts, and then the box wedges solid.

I tried that in a VM running latest Linus tree. I see trinity children 
getting nuked regularly from oom.

I was dumping Vm elements using:

while [ 1 ]; do echo $(date) $(egrep Vm /proc/$pid/status); sleep 1; done

And right before the process is killed was the line:

Fri Jul 12 11:00:19 MDT 2013 VmPeak: 2867472 kB VmSize: 2867472 kB 
VmLck: 0 kB VmPin: 0 kB VmHWM: 1493092 kB VmRSS: 1493092 kB VmData: 
2857944 kB VmStk: 136 kB VmExe: 100 kB VmLib: 1844 kB VmPTE: 5628 kB 
VmSwap: 0 kB

The VmData is growing fairly steadily and strace shows a lot of brk 
calls. Is that normal for trinity - or this command line?

Looking at the perf_event_open calls I see a lot of E2BIG errors in 
addition to EINVAL. e.g,

...
perf_event_open(0xba9000, 0, 0x4c, 0xcc, 0) = -1 EINVAL (Invalid argument)
alarm(0)                                = 1
getppid()                               = 9031
alarm(1)                                = 0
perf_event_open(0xba9000, 0x2a6e, 0xe, 0xfd, 0) = -1 E2BIG (Argument 
list too long)
alarm(0)                                = 1
getppid()                               = 9031
alarm(1)                                = 0
...

David
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