linux-kernel - Re: [PATCH] perf report: Provide libtraceevent with a kernel symbol resolver

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Date:   Wed, 17 Jan 2018 00:48:12 +0800
From:   Wang YanQing <udknight@...il.com>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     acme@...nel.org, peterz@...radead.org, mingo@...hat.com,
        alexander.shishkin@...ux.intel.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] perf report: Provide libtraceevent with a kernel symbol
 resolver

On Mon, Jan 15, 2018 at 11:06:11AM +0100, Jiri Olsa wrote:
> On Mon, Jan 15, 2018 at 12:47:32PM +0800, Wang YanQing wrote:
> > So that beautifiers wanting to resolve kernel function addresses to
> > names can do its work, and when we use "perf report" for output of
> > "perf kmem record", we will get kernel symbol output.
> > 
> > Signed-off-by: Wang YanQing <udknight@...il.com>
> > ---
> >  tools/perf/builtin-report.c | 9 +++++++++
> >  1 file changed, 9 insertions(+)
> > 
> > diff --git a/tools/perf/builtin-report.c b/tools/perf/builtin-report.c
> > index dd4df9a..7b65100 100644
> > --- a/tools/perf/builtin-report.c
> > +++ b/tools/perf/builtin-report.c
> > @@ -1317,6 +1317,15 @@ int cmd_report(int argc, const char **argv)
> >  		report.range_num = 1;
> >  	}
> >  
> > +	if (session->tevent.pevent &&
> > +	    pevent_set_function_resolver(session->tevent.pevent,
> > +					 machine__resolve_kernel_addr,
> > +					 &session->machines.host) < 0) {
> > +		pr_err("%s: failed to set libtraceevent function resolver\n",
> > +		       __func__);
> > +		return -1;
> > +	}
> 
> why not calling the wrapper trace_event__register_resolver?
The reason is the same as builtin-script doesn't use trace_event__register_resolver,
because we only use report and script to analyze offline perf.data, and there could
be no tracepoints in perf.data.

The wrapper trace_event__register_resolver always initialize tevent.pevent, and calling
pevent_set_function_resolver which isn't necessary when there is no tracepoints in the
perf.data.
> 
> jirka
> 
> > +
> >  	sort__setup_elide(stdout);
> >  
> >  	ret = __cmd_report(&report);
> > -- 
> > 1.8.5.6.2.g3d8a54e.dirty
> >