linux-kernel - Re: [GIT PULL] perf changes for v3.8

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Date:	Sun, 23 Dec 2012 16:17:45 -0700
From:	David Ahern <dsahern@...il.com>
To:	Gleb Natapov <gleb@...hat.com>
CC:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [GIT PULL] perf changes for v3.8

On 12/23/12 2:23 AM, Gleb Natapov wrote:
>> Your patch alone was not enough. Start here:
>>   https://lkml.org/lkml/2012/7/12/3
>>
> I cannot reproduce this failure. I reverted 20b279ddb38c and ran "perf
> record -e cycles:ppG" while guest was running. Admittedly I ran the test
> for a short time, but without disabling PEBS during the guest entry this
> was enough to crash a guest.

In the beginning (without any patches) VMs crashed fairly quickly. With 
your patch it took longer, but I was able to consistently crash VMs. The 
thread notes server info (processor, OS) and VM versions as well as load 
used for the tests -- a cpu bound process (openssl), disk bound (dd) and 
network (netperf).


> What about forcing exclude_guest on an event that
> has precise flag set without reporting error to userspace?

That's up to the perf maintainers -- Ingo, Peter, Arnaldo. Personally, I 
don't like it since kernel side is changing the user request.

David
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