Messages in this thread Patch in this message | | | Date | Tue, 14 Nov 2023 13:12:54 -0800 | Subject | [RFC PATCH v1] perf evsel: Fallback to task-clock when not system wide | From | Ian Rogers <> |
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When the cycles event isn't available evsel will fallback to the cpu-clock software event. task-clock is similar to cpu-clock but only runs when the process is running. Falling back to cpu-clock when not system wide leads to confusion, by falling back to task-clock it is hoped the confusion is less.
Update a nearby comment and debug string for the change.
Signed-off-by: Ian Rogers <irogers@google.com> --- tools/perf/util/evsel.c | 15 ++++++++------- 1 file changed, 8 insertions(+), 7 deletions(-)
diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c index a5da74e3a517..e1175313e4bc 100644 --- a/tools/perf/util/evsel.c +++ b/tools/perf/util/evsel.c @@ -2861,18 +2861,19 @@ bool evsel__fallback(struct evsel *evsel, int err, char *msg, size_t msgsize) evsel->core.attr.type == PERF_TYPE_HARDWARE && evsel->core.attr.config == PERF_COUNT_HW_CPU_CYCLES) { /* - * If it's cycles then fall back to hrtimer based - * cpu-clock-tick sw counter, which is always available even if - * no PMU support. + * If it's cycles then fall back to hrtimer based cpu-clock sw + * counter, which is always available even if no PMU support. * * PPC returns ENXIO until 2.6.37 (behavior changed with commit * b0a873e). */ - scnprintf(msg, msgsize, "%s", -"The cycles event is not supported, trying to fall back to cpu-clock-ticks"); - evsel->core.attr.type = PERF_TYPE_SOFTWARE; - evsel->core.attr.config = PERF_COUNT_SW_CPU_CLOCK; + evsel->core.attr.config = evsel->core.system_wide + ? PERF_COUNT_SW_CPU_CLOCK + : PERF_COUNT_SW_TASK_CLOCK; + scnprintf(msg, msgsize, + "The cycles event is not supported, trying to fall back to %s", + evsel->core.system_wide ? "cpu-clock" : "task-clock"); zfree(&evsel->name); return true; -- 2.43.0.rc0.421.g78406f8d94-goog
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