Messages in this thread Patch in this message | | | From | Athira Rajeev <> | Subject | [PATCH V2] perf/core: Avoid calling perf_mux_hrtimer_restart multiple times when scheduling event groups | Date | Tue, 26 Oct 2021 14:17:09 +0530 |
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Perf uses multiplexing if there are more events to be scheduled than the available counters. With multiplexing, event groups will be rotated at specified interval of time which is set using "hrtimer". During event scheduling, if any of the event group fails to schedule, multiplexing gets enabled by setting "rotate_necessary" for that event context and starting the hrtimer by calling "perf_mux_hrtimer_restart".
Patch adds an optimisation to avoid calling "perf_mux_hrtimer_restart" multiple times if already rotate_necessary is set for that context. Even though "perf_mux_hrtimer_restart" will just return if hrtimer is already active, this could avoid the overhead of calling this function multiple times if there are many event groups. Patch adds the check to avoid calling perf_mux_hrtimer_restart() for each event group on every schedule.
Signed-off-by: Athira Rajeev <atrajeev@linux.vnet.ibm.com> Acked-by: Song Liu <song@kernel.org> --- Changelog: From v1 -> v2: - Rebased on top of latest kernel source. - Added Acked-by from Song Liu
kernel/events/core.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/kernel/events/core.c b/kernel/events/core.c index f23ca260307f..9e1a06646ad0 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -3753,8 +3753,10 @@ static int merge_sched_in(struct perf_event *event, void *data) perf_cgroup_event_disable(event, ctx); perf_event_set_state(event, PERF_EVENT_STATE_ERROR); } else { - ctx->rotate_necessary = 1; - perf_mux_hrtimer_restart(cpuctx); + if (!ctx->rotate_necessary) { + ctx->rotate_necessary = 1; + perf_mux_hrtimer_restart(cpuctx); + } group_update_userpage(event); } } -- 2.33.0
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