Messages in this thread Patch in this message | | | Date | Tue, 10 Dec 2013 14:44:52 -0500 (EST) | From | Vince Weaver <> | Subject | [patch v2] perf tools: perf list broken on ARM |
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Hello,
"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>
diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c index 6de6f89..07b6e2d 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; @@ -1099,8 +1099,24 @@ 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; perf_evsel__delete(evsel); + + 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. + * + */ + attr.exclude_kernel = 1; + evsel = perf_evsel__new(&attr); + + ret = perf_evsel__open(evsel, NULL, &tmap.map) >= 0; + perf_evsel__delete(evsel); + } } return ret;
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