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

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Date:	Mon, 2 Aug 2010 18:03:53 +1000
From:	Nick Piggin <npiggin@...e.de>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Nick Piggin <npiggin@...e.de>,
	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

On Mon, Aug 02, 2010 at 09:54:22AM +0200, Ingo Molnar wrote:
> 
> * 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.

"noise" sounds like false positives though. Certainly if this is
instead allows valgrind to run in a particular mode that assumes
no application resources consumed at exit(2) time, I wouldn't
call it crappy :)

But you could equally sprinkle in other valgrind specific annotations
or semantics at various points in the code to improve its coverage,
no?
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