linux-kernel - Re: [RFC 00/14] perf pollfd v3

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Date:	Tue, 23 Sep 2014 14:52:58 +0200
From:	Jiri Olsa <jolsa@...hat.com>
To:	Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:	linux-kernel@...r.kernel.org,
	Adrian Hunter <adrian.hunter@...el.com>,
	Borislav Petkov <bp@...e.de>,
	Corey Ashford <cjashfor@...ux.vnet.ibm.com>,
	David Ahern <dsahern@...il.com>,
	Don Zickus <dzickus@...hat.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...nel.org>,
	Jean Pihet <jean.pihet@...aro.org>,
	Mike Galbraith <efault@....de>,
	Namhyung Kim <namhyung@...nel.org>,
	Paul Mackerras <paulus@...ba.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Stephane Eranian <eranian@...gle.com>
Subject: Re: [RFC 00/14] perf pollfd v3

On Tue, Sep 23, 2014 at 09:46:40AM -0300, Arnaldo Carvalho de Melo wrote:
> Em Tue, Sep 23, 2014 at 11:26:45AM +0200, Jiri Olsa escreveu:
> > On Mon, Sep 22, 2014 at 06:10:27PM -0300, Arnaldo Carvalho de Melo wrote:
> > > Em Mon, Sep 22, 2014 at 04:51:33PM +0200, Jiri Olsa escreveu:
> > > > On Mon, Sep 22, 2014 at 11:49:49AM -0300, Arnaldo Carvalho de Melo wrote:
> > > > > Em Mon, Sep 22, 2014 at 03:35:26PM +0200, Jiri Olsa escreveu:
> > > > > > On Thu, Sep 18, 2014 at 01:04:55PM -0300, Arnaldo Carvalho de Melo wrote:
> > > > > > > Em Thu, Sep 11, 2014 at 06:36:38PM -0300, Arnaldo Carvalho de Melo escreveu:
> > > > > > > https://git.kernel.org/cgit/linux/kernel/git/acme/linux.git/log/?h=perf/fdarray.v4
> > > 
> > > > > > > Its on top of my last perf/core branch, i.e. with builtin-record.c using
> > > > > > > perf_evlist__mmap_consume() and it and builtin-trace.c doing one last
> > > > > > > mmap_read loop to consume what is left after all fds for a mmap are
> > > > > > > closed.
> > > 
> > > > > > > I'll wait a bit before reposting, probably Jiri will not be able to
> > > > > > > comment this week, but I would like to at least post the URL for this
> > > > > > > latest v4 kit.
> > > 
> > > > > > > Adrian, if you could take a look at it, would be really great :-)
> > > 
> > > > > > I checked the branch.. the last patch brakes the functionality
> > > > > > of perf record for me
> > > 
> > > > > Breaks in what sense?
> > > 
> > > > perf record -p pid
> > > 
> > > > and killing the pid won't finish perf record
> > > 
> > > Should be ok now, after making sure record uses
> > > perf_evlist__mmap_consume(), which does what you did in your proposed
> > > fix, tried both killing it and letting it exit normally, i.e. a 'sleep 5s'
> > > target.
> > > 
> > > Pushed
> > > https://git.kernel.org/cgit/linux/kernel/git/acme/linux.git/log/?h=perf/fdarray.v6
> > > after moving the changesets for trace and record to be done last,
> > > waiting for all fds to be POLLHUP'ed and doing one last draining
> > > mmap_read loop over the mmaps.
> > 
> > One more thing is I noticed the test 34 is segfaulting, because
> > perf_evlist__munmap_filtered assumes priv pointer setup, which
> > is not done in the test.
> 
> Yeah, forgot to update it wrt mmap refcounting.
> 
> But this brought to my attention the difficulty in debugging perf test
> entries these days, because we do a fork + exec there, I tried using gdb
> and I must be missing something, because I couldn't add a breakpoint
> inside the tests :-\

you need to run following gdb command:

(gdb) set follow-fork-mode child

jirka
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