Re: [PATCH RESEND] perf record: Add --buildid-all option

[Arnaldo Carvalho de Melo <acme@kernel.org>]

Em Tue, Jan 12, 2016 at 02:28:22PM +0200, Adrian Hunter escreveu:
> On 11/01/16 15:38, Namhyung Kim wrote:
> > The --buildid-all option is to record build-id of all DSOs in the file.
> > It might be very costly to postprocess samples to find which DSO hits.
> >
> > Cc: Adrian Hunter <adrian.hunter@intel.com>
> > Cc: Andi Kleen <andi@firstfloor.org>
> > Cc: Stephane Eranian <eranian@google.com>
> > Signed-off-by: Namhyung Kim <namhyung@kernel.org>
> > ---
> >  tools/perf/Documentation/perf-record.txt |  3 +++
> >  tools/perf/builtin-record.c              | 32 ++++++++++++++++++++++++++------
> >  2 files changed, 29 insertions(+), 6 deletions(-)
> >
> > diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt
> > index 3a1a32f5479f..fbceb631387c 100644
> > --- a/tools/perf/Documentation/perf-record.txt
> > +++ b/tools/perf/Documentation/perf-record.txt
> > @@ -338,6 +338,9 @@ Options passed to clang when compiling BPF scriptlets.
> >  Specify vmlinux path which has debuginfo.
> >  (enabled when BPF prologue is on)
> >  
> > +--buildid-all::
> > +Record build-id of all DSOs regardless whether it's actually hit or not.
> > +
> >  SEE ALSO
> >  --------
> >  linkperf:perf-stat[1], linkperf:perf-list[1]
> > diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
> > index dc4e0adf5c5b..a42cb2955697 100644
> > --- a/tools/perf/builtin-record.c
> > +++ b/tools/perf/builtin-record.c
> > @@ -50,6 +50,7 @@ struct record {
> >  	int			realtime_prio;
> >  	bool			no_buildid;
> >  	bool			no_buildid_cache;
> > +	bool			buildid_all;
> >  	unsigned long long	samples;
> >  };
> >  
> > @@ -362,6 +363,13 @@ static int process_buildids(struct record *rec)
> >  	 */
> >  	symbol_conf.ignore_vmlinux_buildid = true;
> >  
> > +	/*
> > +	 * If --buildid-all is given, it marks all DSO regardless of hits,
> > +	 * so no need to process samples.
> > +	 */
> > +	if (rec->buildid_all)
> > +		rec->tool.sample = NULL;
> 
> I wonder, if we are not processing samples, could the processing could be
> much simpler?
> All we need to do is read all the MMAP events, in any order, and create DSOs
> - no need to
> create threads or map-groups etc etc.

Right, if that was the overhead, have you ever measured this?

- Arnaldo