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SubjectRe: [patch] perf tools: perf list broken on ARM

just checking on the status of this patch. Am I sending it to the wrong
place? Did it get lost in the post-holiday e-mail purges?

The bug is annoying if you're trying to use perf on ARM systems.

Vince

On Mon, 30 Dec 2013, Vince Weaver wrote:

>
> "perf list" listing of hardware events doesn't work on older ARM devices.
> The change enabling event detection:
>
> commit b41f1cec91c37eeea6fdb15effbfa24ea0a5536b
> Author: Namhyung Kim <namhyung.kim@lge.com>
> Date: Tue Aug 27 11:41:53 2013 +0900
>
> perf list: Skip unsupported events
>
>
> uses the following code in tools/perf/util/parse-events.c:
>
> struct perf_event_attr attr = {
> .type = type,
> .config = config,
> .disabled = 1,
> .exclude_kernel = 1,
> };
>
> On ARM machines pre-dating the Cortex-A15 this doesn't work, as
> these machines don't support .exclude_kernel. So starting with 3.12
> "perf list" does not report any hardware events at all on older
> machines (seen on Rasp-Pi, Pandaboard, Beagleboard, etc).
>
> This version of the patch makes changes suggested by Namhyung Kim
> to check for EACCESS and retry (instead of just dropping
> the exclude_kernel) so we can properly handle machines where
> /proc/sys/kernel/perf_event_paranoid is set to 2.
>
> Reported-by: Chad Paradis <chad.paradis@umit.maine.edu>
> Signed-off-by: Vince Weaver <vincent.weaver@maine.edu>
> Acked-by: Namhyung Kim <namhyung@kernel.org>
>
> diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
> index 6de6f89..1fa98b9 100644
> --- a/tools/perf/util/parse-events.c
> +++ b/tools/perf/util/parse-events.c
> @@ -1082,12 +1082,12 @@ int is_valid_tracepoint(const char *event_string)
> static bool is_event_supported(u8 type, unsigned config)
> {
> bool ret = true;
> + int open_return;
> struct perf_evsel *evsel;
> struct perf_event_attr attr = {
> .type = type,
> .config = config,
> .disabled = 1,
> - .exclude_kernel = 1,
> };
> struct {
> struct thread_map map;
> @@ -1099,7 +1099,20 @@ static bool is_event_supported(u8 type, unsigned config)
>
> evsel = perf_evsel__new(&attr);
> if (evsel) {
> - ret = perf_evsel__open(evsel, NULL, &tmap.map) >= 0;
> + open_return = perf_evsel__open(evsel, NULL, &tmap.map);
> + ret = open_return >= 0;
> +
> + if (open_return == -EACCES) {
> + /*
> + * This happens if the paranoid value
> + * /proc/sys/kernel/perf_event_paranoid is set to 2
> + * Re-run with exclude_kernel set; we don't do that
> + * by default as some ARM machines do not support it.
> + *
> + */
> + evsel->attr.exclude_kernel = 1;
> + ret = perf_evsel__open(evsel, NULL, &tmap.map) >= 0;
> + }
> perf_evsel__delete(evsel);
> }
>
>

Vince Weaver
vincent.weaver@maine.edu
http://www.eece.maine.edu/~vweaver/


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