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| author | Namhyung Kim <namhyung@kernel.org> | 2024-02-06 21:05:45 -0800 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2024-04-10 06:13:57 +0200 |
| commit | f38628b06c36222367e26820879789ae59e49f60 (patch) | |
| tree | 3a2cea20a240a80f2d5bbf7df451221d05241a1f /kernel/events/core.c | |
| parent | 0259bf63f71e2accfeca4a4e346ede8edcc86aab (diff) | |
| download | linux-stable-f38628b06c36222367e26820879789ae59e49f60.tar.gz linux-stable-f38628b06c36222367e26820879789ae59e49f60.tar.bz2 linux-stable-f38628b06c36222367e26820879789ae59e49f60.zip | |
perf/core: Reduce PMU access to adjust sample freq
In perf_adjust_freq_unthr_context(), it first starts the event and then
stop unnecessarily to adjust the sampling frequency if the event is
throttled.
For a throttled non-frequency event, it doesn't have a freq so no need
to adjust. Just starting the event would be ok.
For a frequency event, whether it's throttled or not, it needs to stop
before adjusting the frequency. That means it should not start the
even if it was throttled. I tried to skip calling the stop callback,
but it didn't work well since the event count might not be up to date.
It should call the stop callback with PERF_EF_UPDATE anyway.
However not calling start would prevent unnecessary MSR accesses (which
can be costly) for already stopped events as stop state is saved in the
hw config.
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Ian Rogers <irogers@google.com>
Reviewed-by: Kan Liang <kan.liang@linux.intel.com>
Link: https://lore.kernel.org/r/20240207050545.2727923-2-namhyung@kernel.org
Diffstat (limited to 'kernel/events/core.c')
| -rw-r--r-- | kernel/events/core.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/kernel/events/core.c b/kernel/events/core.c index 9566cfb27355..fd94e45a9d86 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -4146,7 +4146,8 @@ static void perf_adjust_freq_unthr_events(struct list_head *event_list) if (hwc->interrupts == MAX_INTERRUPTS) { hwc->interrupts = 0; perf_log_throttle(event, 1); - event->pmu->start(event, 0); + if (!event->attr.freq || !event->attr.sample_freq) + event->pmu->start(event, 0); } if (!event->attr.freq || !event->attr.sample_freq) |