Re: [PATCH] perf-record: Create events initially disabled -- again

[David Ahern]

On 5/14/12 1:40 AM, Namhyung Kim wrote:
> Hi,
>
> On Sun, 13 May 2012 22:01:28 -0600, David Ahern wrote:
> > 764e16a changed perf-record to create events disabled by default and
> > enable them once perf initializations are done. This setting was dropped
> > by 0f82ebc. Now perf events are once again generated during perf's
> > initialization phase (e.g., generating maps).
> >
> > As an example, perf opens a lot of files at startup. Unpatched:
> >
> > perf record -e syscalls:sys_enter_open -ga -fo /tmp/perf.data -- sleep 1
> > [ perf record: Woken up 1 times to write data ]
> > [ perf record: Captured and wrote 0.087 MB /tmp/perf.data (~3798 samples) ]
> >
> > Using perf-script to look at the samples shows the perf command generating
> > 563 of the 566 total events.
> >
> > Patched:
> >
> > perf record -e syscalls:sys_enter_open -ga -fo /tmp/perf.data -- sleep 1
> > [ perf record: Woken up 1 times to write data ]
> > [ perf record: Captured and wrote 0.028 MB /tmp/perf.data (~1206 samples) ]
> >
> > Using perf-script to look at the samples does not show perf command.
> >
> > Signed-off-by: David Ahern<dsahern@xxxxxxxxx>
> > ---
> >   tools/perf/util/evsel.c |    2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
> > index 21eaab2..6710cfe 100644
> > --- a/tools/perf/util/evsel.c
> > +++ b/tools/perf/util/evsel.c
> > @@ -70,6 +70,7 @@ void perf_evsel__config(struct perf_evsel *evsel, struct perf_record_opts *opts,
> >   	struct perf_event_attr *attr =&evsel->attr;
> >   	int track = !evsel->idx; /* only the first counter needs these */
> >
> > +	attr->disabled = 1;
> >   	attr->sample_id_all = opts->sample_id_all_missing ? 0 : 1;
> >   	attr->inherit	    = !opts->no_inherit;
> >   	attr->read_format   = PERF_FORMAT_TOTAL_TIME_ENABLED |
> > @@ -138,7 +139,6 @@ void perf_evsel__config(struct perf_evsel *evsel, struct perf_record_opts *opts,
> >
> >   	if (perf_target__none(&opts->target)&&
> >   	(!opts->group || evsel == first)) {
> > -		attr->disabled = 1;
> >   		attr->enable_on_exec = 1;
> >   	}
> >   }
>
> A problem I see is that it'll break group handling again:
>
> $ ./perf stat -g sleep 1
>
>   Performance counter stats for 'sleep 1':
>
>       <not counted>  task-clock
>       <not counted>  context-switches
>       <not counted>  CPU-migrations
>       <not counted>  page-faults
>       <not counted>  cycles
>       <not counted>  stalled-cycles-frontend
>       <not counted>  stalled-cycles-backend
>       <not counted>  instructions
>       <not counted>  branches
>       <not counted>  branch-misses
>
>         1.000868932 seconds time elapsed
>
> So I suggest changing perf_target__none() check to a proper one
> (perf_target__no_cpu? - the name might be changed soon) for your
> purpose.
>
> Thanks,
> Namhyung

Something else is wrong then. I tested that command (saw your patch in 
the history) and it worked for me. Also, this code path does not affect 
perf-stat -- it touches perf-record and perf-test only.

David
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