Re: [PATCH 1/1] rasd: Use perf_evlist__open() instead of open coded

Jean Pihet
2014-10-07T08:45:31Z

Hi Arnaldo,

On 6 October 2014 23:26, Arnaldo Carvalho de Melo <acme@kernel.org> wrote:
> Heya, please check if this is OK.
>
> This was while looking the set of methods used by rasd, trying to reduce
> it to the bare minimum.
>
> Perhaps even that cpu_map__new() one can be ditched, leaving to use the
> default of a NULL cpumap that will end up being one with -1, i.e. all
> cpus.
>
> - Arnaldo
>
> From 8dc34bd2824c7843182f4fc6deabaf573e42e806 Mon Sep 17 00:00:00 2001
> From: Arnaldo Carvalho de Melo <acme@redhat.com>
> Date: Mon, 6 Oct 2014 15:43:42 -0300
> Subject: [PATCH] rasd: Use perf_evlist__open() instead of open coded
> equivalent
>
> Cc: Borislav Petkov <bp@suse.de>
> Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
> ---
> src/rasd.c | 10 +++-------
> 1 file changed, 3 insertions(+), 7 deletions(-)
>
> diff --git a/src/rasd.c b/src/rasd.c
> index 06ccdcdd9d56..fb33fca131fa 100644
> --- a/src/rasd.c
> +++ b/src/rasd.c
> @@ -241,7 +241,6 @@ static void daemonize(void)
>
> int main()
> {
> - struct perf_evsel *c;
> struct thread_map *threads;
> struct cpu_map *cpus;
> int i;
> @@ -278,12 +277,9 @@ int main()
> perf_evlist__set_maps(evlist, cpus, threads);
>
> /* Open events */
> - evlist__for_each(evlist, c) {
> - /* On all online cpus by default, system wide tracing */
> - if (perf_evsel__open(c, evlist->cpus, NULL) < 0)
> - err("opening tracepoint, are you root?");
> - }
> - perf_evlist__set_id_pos(evlist);
> + /* On all online cpus by default, system wide tracing */
> + if (perf_evlist__open(evlist) < 0)
> + err("opening tracepoint, are you root?");

That way the system wide tracing does not work. perf_evlist__open uses
a non-NULL thread mapping and so it only traces the events generated
by the daemon itself.

perf top uses a similar approach but uses a lot of code in machine.c
(machine__synthesize_threads) and util/event.c
(perf_event__synthesize_threads) to synthesize the threads etc., which
we want to avoid in the minimalistic approach of rasd.

Maybe I missed something about the system wide tracing, any suggestion
is welcome.

Thanks for looking!

Jean

>
> /* mmap buffers */
> if (perf_evlist__mmap(evlist, 4 /* opts->mmap_pages */, false) < 0)
> --
> 1.9.3
>