linux-kernel - Re: [RFC 2/2] x86_64, mm: Reinsert the absent memory

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Message-ID: <51CB12BC.9080708@sgi.com>
Date:	Wed, 26 Jun 2013 11:11:40 -0500
From:	Nathan Zimmer <nzimmer@....com>
To:	Ingo Molnar <mingo@...nel.org>
CC:	Dave Hansen <dave.hansen@...el.com>, <holt@....com>,
	<travis@....com>, <rob@...dley.net>, <tglx@...utronix.de>,
	<mingo@...hat.com>, <hpa@...or.com>, <yinghai@...nel.org>,
	<akpm@...ux-foundation.org>, <gregkh@...uxfoundation.org>,
	<x86@...nel.org>, <linux-doc@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [RFC 2/2] x86_64, mm: Reinsert the absent memory

On 06/26/2013 10:58 AM, Ingo Molnar wrote:
> * Nathan Zimmer <nzimmer@....com> wrote:
>
>> On 06/26/2013 10:12 AM, Dave Hansen wrote:
>>> On 06/26/2013 07:49 AM, Nathan Zimmer wrote:
>>>> My guess it is the NMIs overwhelming the system but I have not found a good way
>>>> to profile perf gone wild so it is only a guess.
>>> I've got an 80-core system and the symptoms sound similar to perf issues
>>> I'm seeing.  Dropping the sample rate helped for me, and there's a patch
>>> in -tip at the moment to do it automatically:
>>>
>>>> http://git.kernel.org/cgit/linux/kernel/git/tip/tip.git/commit/?id=14c63f17b1fde5a575a28e96547a22b451c71fb5
>>> Looks like you've also found that debugging NMIs is fun. :)
>> More fun then one person can handle.
>> I'll have to take this patch for a spin.
> Please try latest -tip:master, there's a series of patches from Dave that
> address this problem category.
>
> Does it only happen with -g, or with regular perf record and/or with perf
> top as well?
>
> Thanks,
>
> 	Ingo

It happens in all those cases, but I notice it most when doing a perf 
record -g -a
I'll try the tip series and see how it compares.

Thanks
     Nate
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