linux-kernel - Re: [PATCH 1/3] perf: add context field to perf

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Message-ID: <20110712102417.GD29812@8bytes.org>
Date:	Tue, 12 Jul 2011 12:24:17 +0200
From:	Joerg Roedel <joro@...tes.org>
To:	Avi Kivity <avi@...hat.com>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Will Deacon <will.deacon@....com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	Ingo Molnar <mingo@...e.hu>,
	"acme@...stprotocols.net" <acme@...stprotocols.net>,
	Jason Wessel <jason.wessel@...driver.com>
Subject: Re: [PATCH 1/3] perf: add context field to perf_event

On Tue, Jul 12, 2011 at 01:07:25PM +0300, Avi Kivity wrote:
> On 07/12/2011 01:03 PM, Joerg Roedel wrote:

>> Ingo made perf-integration a merge-requirement for LWP. It is not really
>> well-suited for being integrated into perf because the design goal was
>> easy and efficient self-profiling of tasks (like you stated). So
>> integrating it into perf causes some pain. But lets see how it works
>> out.
>
> I don't think it's workable.  Having do_mmap() called in the task's  
> context can change how it works.

According to Ingo that is already done at other places in the kernel and
should not be an issue.

> And the task being able to kill/modify  the profile, and not able to
> use LWP for itself, is a show stopper IMO.

I agree, that is a problem we have no solution for so far.

	Joerg

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