Commit-ID: 8d5bce0c37fa10f21dbdd6a6d8fcba85202fe24e
Gitweb: https://git.kernel.org/tip/8d5bce0c37fa10f21dbdd6a6d8fcba85202fe24e
Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate: Fri, 9 Mar 2018 14:56:27 +0100
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Mon, 12 Mar 2018 15:28:50 +0100
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@xxxxxxxxxxxxx>
Cc: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Stephane Eranian <eranian@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Vince Weaver <vincent.weaver@xxxxxxxxx>
Cc: linux-kernel@xxxxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
kernel/events/core.c | 60 ++++++++++++++++++++++++++++++++--------------------
1 file 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)
--
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