linux-kernel - Re: [PATCH 11/19] perf record: Release resources at exit

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Message-ID: <20100802075422.GA24085@elte.hu>
Date:	Mon, 2 Aug 2010 09:54:22 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Nick Piggin <npiggin@...e.de>
Cc:	Arnaldo Carvalho de Melo <acme@...radead.org>,
	linux-kernel@...r.kernel.org,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Mike Galbraith <efault@....de>,
	Peter Zijlstra <peterz@...radead.org>,
	Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH 11/19] perf record: Release resources at exit


* Nick Piggin <npiggin@...e.de> wrote:

> On Sun, Aug 01, 2010 at 10:08:46PM -0300, Arnaldo Carvalho de Melo wrote:
> > From: Arnaldo Carvalho de Melo <acme@...hat.com>
> > 
> > So that we can reduce the noise on valgrind when looking for memory
> > leaks.
> 
> Really? That's rather crappy of valgrind. exit is well defined to release 
> resources and that's often a more efficient way to do it It finds and 
> batches things a lot better, eg. it can avoid all TLB flushing of freeing 
> memory that munmap requires.

That's certainly true but there's no valgrind crappiness here: valgrind simply 
can do a better job of finding leaks if there's a well defined "all resources 
the app still knows about are freed now" point.

The _kernel_ obviously can release all resources. The distinction is between 
'resources known to the app' and 'all resources'. That set contains the 
leaking resources.

Thanks,

	Ingo
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