From: Ingo Molnar <mingo@elte.hu>
To: Nick Piggin <npiggin@suse.de>
Cc: Arnaldo Carvalho de Melo <acme@infradead.org>,
linux-kernel@vger.kernel.org,
Arnaldo Carvalho de Melo <acme@redhat.com>,
Frederic Weisbecker <fweisbec@gmail.com>,
Mike Galbraith <efault@gmx.de>,
Peter Zijlstra <peterz@infradead.org>,
Stephane Eranian <eranian@google.com>
Subject: Re: [PATCH 11/19] perf record: Release resources at exit
Date: Mon, 2 Aug 2010 11:17:14 +0200 [thread overview]
Message-ID: <20100802091714.GA6781@elte.hu> (raw)
In-Reply-To: <20100802080353.GA8713@amd>
* Nick Piggin <npiggin@suse.de> wrote:
> On Mon, Aug 02, 2010 at 09:54:22AM +0200, Ingo Molnar wrote:
> >
> > * Nick Piggin <npiggin@suse.de> wrote:
> >
> > > On Sun, Aug 01, 2010 at 10:08:46PM -0300, Arnaldo Carvalho de Melo wrote:
> > > > From: Arnaldo Carvalho de Melo <acme@redhat.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. [...]
Every predictive bug detection scheme is open to the potential of false
positives. I've yet to see a complex one that is 100% false positive free.
> [...] 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 :)
Most apps free their stuff before they exit - i do it in all my own C apps.
That is generally useful: for example it makes it easier to thread a program
later on - when exit() becomes pthread_exit() and a silent leak turns into a
real leak.
Hence Valgrind checking for exit() by default looks useful to me.
> But you could equally sprinkle in other valgrind specific annotations or
> semantics at various points in the code to improve its coverage, no?
Yeah, and exit() sounds like a pretty convenient point, right? That's the
point where all resources are inactive hence a scan for leaks is expected to
be the most efficient in finding real leaks.
Thanks,
Ingo
next prev parent reply other threads:[~2010-08-02 9:17 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1280711334-30000-1-git-send-email-acme@infradead.org>
2010-08-02 1:08 ` [PATCH 01/19] perf hists: Mark entries filtered by parent Arnaldo Carvalho de Melo
2010-08-02 1:08 ` [PATCH 02/19] perf sort: Make column width code per hists instance Arnaldo Carvalho de Melo
2010-08-02 1:08 ` [PATCH 03/19] perf ui: Restore SPACE as an alias to PGDN in annotate Arnaldo Carvalho de Melo
2010-08-02 1:08 ` [PATCH 04/19] perf hist: Introduce routine to measure lenght of formatted entry Arnaldo Carvalho de Melo
2010-08-02 1:08 ` [PATCH 05/19] perf ui: Consider the refreshed dimensions in ui_browser__show Arnaldo Carvalho de Melo
2010-08-02 1:08 ` [PATCH 06/19] perf ui: Show the scroll bar over the left window frame Arnaldo Carvalho de Melo
2010-08-02 1:08 ` [PATCH 07/19] perf ui: New hists tree widget Arnaldo Carvalho de Melo
2010-08-02 1:08 ` [PATCH 08/19] perf report: Don't abbreviate file paths relative to the cwd Arnaldo Carvalho de Melo
2010-08-02 1:08 ` [PATCH 09/19] perf tools: Remove unneeded code for tracking the cwd in perf sessions Arnaldo Carvalho de Melo
2010-08-02 1:08 ` [PATCH 10/19] perf man pages: Fix cut'n'paste error Arnaldo Carvalho de Melo
2010-08-02 1:08 ` [PATCH 11/19] perf record: Release resources at exit Arnaldo Carvalho de Melo
2010-08-02 7:30 ` Nick Piggin
2010-08-02 7:54 ` Ingo Molnar
2010-08-02 8:03 ` Nick Piggin
2010-08-02 9:17 ` Ingo Molnar [this message]
2010-08-02 9:59 ` Nick Piggin
2010-08-02 14:49 ` Arnaldo Carvalho de Melo
2010-08-02 8:08 ` Pekka Enberg
2010-08-02 1:08 ` [PATCH 12/19] perf symbols: Precisely specify if dso->{long,short}_name should be freed Arnaldo Carvalho de Melo
2010-08-02 1:08 ` [PATCH 13/19] perf tools: Factor out buildid reading and make it implicit in dso__load Arnaldo Carvalho de Melo
2010-08-02 1:08 ` [PATCH 14/19] perf tools: remove extra build-id check factored into dso__load Arnaldo Carvalho de Melo
2010-08-02 1:08 ` [PATCH 15/19] perf symbols: Improve debug image search when loading symbols Arnaldo Carvalho de Melo
2010-08-02 1:08 ` [PATCH 16/19] perf tui: Make CTRL+Z suspend perf Arnaldo Carvalho de Melo
2010-08-02 1:08 ` [PATCH 17/19] perf probe: Rename common fields/functions from kprobe to probe Arnaldo Carvalho de Melo
2010-08-02 1:08 ` [PATCH 18/19] perf tools: Release thread resources on PERF_RECORD_EXIT Arnaldo Carvalho de Melo
2010-08-02 1:08 ` [PATCH 19/19] perf tools: Release session and symbol resources on exit Arnaldo Carvalho de Melo
2010-08-02 6:26 ` [PATCH 00/19] perf/core improvements and fixes Ingo Molnar
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