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author | Peter Zijlstra <peterz@infradead.org> | 2018-03-09 14:56:27 +0100 |
---|---|---|
committer | Ingo Molnar <mingo@kernel.org> | 2018-03-12 15:28:50 +0100 |
commit | 8d5bce0c37fa10f21dbdd6a6d8fcba85202fe24e (patch) | |
tree | 852a2d8d787bd56cd40b5e2db7e4923cec7bcc84 /kernel | |
parent | 8703a7cfe148f73062c568e9a8549ce692104864 (diff) | |
download | linux-stable-8d5bce0c37fa10f21dbdd6a6d8fcba85202fe24e.tar.gz linux-stable-8d5bce0c37fa10f21dbdd6a6d8fcba85202fe24e.tar.bz2 linux-stable-8d5bce0c37fa10f21dbdd6a6d8fcba85202fe24e.zip |
perf/core: Optimize perf_rotate_context() event scheduling
The event schedule order (as per perf_event_sched_in()) is:
- cpu pinned
- task pinned
- cpu flexible
- task flexible
But perf_rotate_context() will unschedule cpu-flexible even if it
doesn't need a rotation.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel')
-rw-r--r-- | kernel/events/core.c | 60 |
1 files changed, 37 insertions, 23 deletions
diff --git a/kernel/events/core.c b/kernel/events/core.c index 460e485220e8..f98c0f88cc94 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -430,7 +430,7 @@ static void update_perf_cpu_limits(void) WRITE_ONCE(perf_sample_allowed_ns, tmp); } -static int perf_rotate_context(struct perf_cpu_context *cpuctx); +static bool perf_rotate_context(struct perf_cpu_context *cpuctx); int perf_proc_update_handler(struct ctl_table *table, int write, void __user *buffer, size_t *lenp, @@ -1041,7 +1041,7 @@ list_update_cgroup_event(struct perf_event *event, static enum hrtimer_restart perf_mux_hrtimer_handler(struct hrtimer *hr) { struct perf_cpu_context *cpuctx; - int rotations = 0; + bool rotations; lockdep_assert_irqs_disabled(); @@ -3600,52 +3600,66 @@ static void rotate_ctx(struct perf_event_context *ctx, struct perf_event *event) perf_event_groups_insert(&ctx->flexible_groups, event); } -static int perf_rotate_context(struct perf_cpu_context *cpuctx) +static inline struct perf_event * +ctx_first_active(struct perf_event_context *ctx) { - struct perf_event *ctx_event = NULL, *cpuctx_event = NULL; + return list_first_entry_or_null(&ctx->flexible_active, + struct perf_event, active_list); +} + +static bool perf_rotate_context(struct perf_cpu_context *cpuctx) +{ + struct perf_event *cpu_event = NULL, *task_event = NULL; + bool cpu_rotate = false, task_rotate = false; struct perf_event_context *ctx = NULL; - int rotate = 0; + + /* + * Since we run this from IRQ context, nobody can install new + * events, thus the event count values are stable. + */ if (cpuctx->ctx.nr_events) { if (cpuctx->ctx.nr_events != cpuctx->ctx.nr_active) - rotate = 1; + cpu_rotate = true; } ctx = cpuctx->task_ctx; if (ctx && ctx->nr_events) { if (ctx->nr_events != ctx->nr_active) - rotate = 1; + task_rotate = true; } - if (!rotate) - goto done; + if (!(cpu_rotate || task_rotate)) + return false; perf_ctx_lock(cpuctx, cpuctx->task_ctx); perf_pmu_disable(cpuctx->ctx.pmu); - cpuctx_event = list_first_entry_or_null(&cpuctx->ctx.flexible_active, - struct perf_event, active_list); - if (ctx) { - ctx_event = list_first_entry_or_null(&ctx->flexible_active, - struct perf_event, active_list); - } + if (task_rotate) + task_event = ctx_first_active(ctx); + if (cpu_rotate) + cpu_event = ctx_first_active(&cpuctx->ctx); - cpu_ctx_sched_out(cpuctx, EVENT_FLEXIBLE); - if (ctx) + /* + * As per the order given at ctx_resched() first 'pop' task flexible + * and then, if needed CPU flexible. + */ + if (task_event || (ctx && cpu_event)) ctx_sched_out(ctx, cpuctx, EVENT_FLEXIBLE); + if (cpu_event) + cpu_ctx_sched_out(cpuctx, EVENT_FLEXIBLE); - if (cpuctx_event) - rotate_ctx(&cpuctx->ctx, cpuctx_event); - if (ctx_event) - rotate_ctx(ctx, ctx_event); + if (task_event) + rotate_ctx(ctx, task_event); + if (cpu_event) + rotate_ctx(&cpuctx->ctx, cpu_event); perf_event_sched_in(cpuctx, ctx, current); perf_pmu_enable(cpuctx->ctx.pmu); perf_ctx_unlock(cpuctx, cpuctx->task_ctx); -done: - return rotate; + return true; } void perf_event_task_tick(void) |