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

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Date:	Wed, 26 Jun 2013 17:58:35 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Nathan Zimmer <nzimmer@....com>
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


* 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
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