Messages in this thread Patch in this message | | | Date | Fri, 15 Sep 2023 20:56:40 -0700 | Subject | [PATCH v1] perf evlist: Avoid frequency mode for the dummy event | From | Ian Rogers <> |
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Dummy events are created with an attribute where the period and freq are zero. evsel__config will then see the uninitialized values and initialize them in evsel__default_freq_period. As fequency mode is used by default the dummy event would be set to use frequency mode. However, this has no effect on the dummy event but does cause unnecessary timers/interrupts. Avoid this overhead by setting the period to 1 for dummy events.
evlist__add_aux_dummy calls evlist__add_dummy then sets freq=0 and period=1. This isn't necessary after this change and so the setting is removed.
Fixes: 5bae0250237f ("perf evlist: Introduce perf_evlist__new_dummy constructor") Reported-by: Stephane Eranian <eranian@google.com> Signed-off-by: Ian Rogers <irogers@google.com> --- tools/perf/util/evlist.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c index 25c3ebe2c2f5..e36da58522ef 100644 --- a/tools/perf/util/evlist.c +++ b/tools/perf/util/evlist.c @@ -251,6 +251,9 @@ static struct evsel *evlist__dummy_event(struct evlist *evlist) .type = PERF_TYPE_SOFTWARE, .config = PERF_COUNT_SW_DUMMY, .size = sizeof(attr), /* to capture ABI version */ + /* Avoid frequency mode for dummy events to avoid associated timers. */ + .freq = 0, + .sample_period = 1, }; return evsel__new_idx(&attr, evlist->core.nr_entries); @@ -277,8 +280,6 @@ struct evsel *evlist__add_aux_dummy(struct evlist *evlist, bool system_wide) evsel->core.attr.exclude_kernel = 1; evsel->core.attr.exclude_guest = 1; evsel->core.attr.exclude_hv = 1; - evsel->core.attr.freq = 0; - evsel->core.attr.sample_period = 1; evsel->core.system_wide = system_wide; evsel->no_aux_samples = true; evsel->name = strdup("dummy:u"); -- 2.42.0.459.ge4e396fd5e-goog
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