linux-kernel - Re: [PATCH v7 11/18] perf tools: add mem access sampling core support

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Date:	Wed, 27 Mar 2013 13:56:45 -0300
From:	Arnaldo Carvalho de Melo <acme@...hat.com>
To:	Stephane Eranian <eranian@...gle.com>
Cc:	Jiri Olsa <jolsa@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>,
	"ak@...ux.intel.com" <ak@...ux.intel.com>,
	Namhyung Kim <namhyung.kim@....com>
Subject: Re: [PATCH v7 11/18] perf tools: add mem access sampling core support

Em Wed, Mar 27, 2013 at 03:48:15PM +0100, Stephane Eranian escreveu:
> On Wed, Mar 27, 2013 at 3:34 PM, Jiri Olsa <jolsa@...hat.com> wrote:
> > On Wed, Mar 27, 2013 at 03:20:14PM +0100, Peter Zijlstra wrote:
> > > On Wed, 2013-03-27 at 15:14 +0100, Jiri Olsa wrote:
> > > > we have correct cpumode for sample->ip, but I think it's the
> > > > PEBS->dla (sample->addr) where we need to guess.. right?

> > > kernel mode very much fakes the cpumode/segment stuff for PEBS. PEBS
> > > assumes you're running in a linear/flat mode.

> > say we hit the sample when kernel accesses the user data, we will endup
> > with IP in kernel space and DATA ptr in user space.. in theory ;-)

> Yes, this is possible. So I think we could probably leaverage ip__resolve_ams()
> and pass the extra parameter for MAP_VARIABLE vs. MAP_FUNCTION.

BTW, I fixed up the patches (kernel and user parts) and have them in
perf/mem at:

git://git.kernel.org/pub/scm/linux/kernel/git/acme/linux

Hope to push it to Ingo today/tomorrow, after some more testing, thanks
Jiri for reviewing it.

Stephane, if you could give it a try again to see that the fixups I did
(documented in the commit logs, just before my Signed-off-by) are ok,
that would be good.

- Arnaldo
 
> 
> >
> > and that would need the cpumode guessing for DATA ptr, because
> > cpumode value is deduced from cs register
> >
> > jirka
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