Re: [PATCH v2 2/5] perf record: Prevent override of attr->sample_period for libpfm4 events

Jiri Olsa
2020-07-28T15:59:56Z

On Tue, Jul 28, 2020 at 01:57:31AM -0700, Ian Rogers wrote:
> From: Stephane Eranian <eranian@google.com>
>
> Before:
> $ perf record -c 10000 --pfm-events=cycles:period=77777
>
> Would yield a cycles event with period=10000, instead of 77777.
>
> This was due to an ordering issue between libpfm4 parsing
> the event string and perf record initializing the event.
>
> This patch fixes the problem by preventing override for
> events with attr->sample_period != 0 by the time
> perf_evsel__config() is invoked. This seems to have been the
> intent of the author.
>
> Signed-off-by: Stephane Eranian <eranian@google.com>
> Reviewed-by: Ian Rogers <irogers@google.com>
> ---
> tools/perf/util/evsel.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
> index 811f538f7d77..8afc24e2ec52 100644
> --- a/tools/perf/util/evsel.c
> +++ b/tools/perf/util/evsel.c
> @@ -976,8 +976,7 @@ void evsel__config(struct evsel *evsel, struct record_opts *opts,
> * We default some events to have a default interval. But keep
> * it a weak assumption overridable by the user.
> */
> - if (!attr->sample_period || (opts->user_freq != UINT_MAX ||
> - opts->user_interval != ULLONG_MAX)) {
> + if (!attr->sample_period) {

I was wondering why this wouldn't break record/top
but we take care of the via record_opts__config

as long as 'perf test attr' works it looks ok to me

Acked-by: Jiri Olsa <jolsa@redhat.com>

thanks,
jirka