linux-kernel - Re: [PATCH] perf report: Fix invalid memory accessing

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Date:	Tue, 8 Sep 2015 12:58:31 -0300
From:	Arnaldo Carvalho de Melo <acme@...nel.org>
To:	Jiri Olsa <jolsa@...hat.com>
Cc:	"Wangnan (F)" <wangnan0@...wei.com>, kan.liang@...el.com,
	linux-kernel@...r.kernel.org, lizefan@...wei.com, pi3orama@....com,
	Adrian Hunter <adrian.hunter@...el.com>,
	Andi Kleen <ak@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>, acme@...hat.com,
	Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH] perf report: Fix invalid memory accessing

Em Tue, Sep 08, 2015 at 12:49:10PM -0300, Arnaldo Carvalho de Melo escreveu:
> Em Tue, Sep 08, 2015 at 05:34:56PM +0200, Jiri Olsa escreveu:
> > On Tue, Sep 08, 2015 at 12:18:13PM -0300, Arnaldo Carvalho de Melo wrote:
> > > Humm, I think that we can have a pointer to the current perf_env, be it
> > > from the current machine, or from the machine environment in the
> > > perf.data file in struct machine, that way we don't need to change that
> > > function prototype, I'm prototyping this now, will post a patch.
> > 
> > I was thinking of that.. but the perf_env is actualyl related to the
> > perf.data not to the current machine.. I think it should be part of
> > the session or perf_header
> 
> But what if I want to trace only events that take place in some specific
> socket, i.e. what to do when perf_session is not used at all and we are
> not dealing with any header, since there are no files involved?

So, this is the continuation of this patch:

commit ce80d3bef9ff97638ca57a5659ef6ad356f35047
Author: Kan Liang <kan.liang@...el.com>
Date:   Fri Aug 28 05:48:04 2015 -0400

    perf tools: Rename perf_session_env to perf_env
    
    As it is not necessarily tied to a perf.data file and needs using in
    places where a perf_session is not required.
    
    Suggested-by: Arnaldo Carvalho de Melo <acme@...hat.com>

-----------------------------

perf_env not necessarily is related to a perf.data file, we need even to
move it away from header.h.

I am looking now at where to populate perf_env and set it to
machine->env when no perf.data files are being accessed.

I  should have seen the use cpu_map__get_socket_id() in
perf_event__preprocess_sample(), that is unnaceptable, as it will parse
that file for each sample, right ;-\

Right now we don't have that much use for the other fields in
'perf_env', just for the CPU topology information, that we will set in
addr_location for each sample, but we can have uses for that later,
think about a TUI interface for 'perf trace' where we will show what was
the command line, etc.

- Arnaldo
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