[PATCH V2 04/13] perf/core: output multiplexing overhead

[kan . liang]

From: Kan Liang <kan.li...@intel.com>

Multiplexing overhead is one of the key overhead when the number of
events is more than available counters.

The multiplexing overhead PERF_CORE_MUX_OVERHEAD is a common overhead
type.

Signed-off-by: Kan Liang <kan.li...@intel.com>
---
 include/linux/perf_event.h      |  2 ++
 include/uapi/linux/perf_event.h |  1 +
 kernel/events/core.c            | 14 ++++++++++++++
 3 files changed, 17 insertions(+)

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index ebd356e..351d321 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -794,6 +794,8 @@ struct perf_cpu_context {
 
        struct list_head                sched_cb_entry;
        int                             sched_cb_usage;
+
+       struct perf_overhead_entry      mux_overhead;
 };
 
 struct perf_output_handle {
diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
index fe7b1fb..355086f 100644
--- a/include/uapi/linux/perf_event.h
+++ b/include/uapi/linux/perf_event.h
@@ -999,6 +999,7 @@ struct perf_branch_entry {
  */
 enum perf_record_overhead_type {
        PERF_CORE_OVERHEAD       = 0,
+       PERF_CORE_MUX_OVERHEAD   = 0,
 
        PERF_PMU_OVERHEAD        = 20,
        PERF_PMU_SAMPLE_OVERHEAD = 20,
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 306bc92..025a19d 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -1830,6 +1830,9 @@ event_sched_out(struct perf_event *event,
        if (event->attr.exclusive || !cpuctx->active_oncpu)
                cpuctx->exclusive = 0;
 
+       if (log_overhead && cpuctx->mux_overhead.nr)
+               perf_log_overhead(event, PERF_CORE_MUX_OVERHEAD, 
&cpuctx->mux_overhead);
+
        perf_pmu_enable(event->pmu);
 }
 
@@ -3330,9 +3333,17 @@ static void rotate_ctx(struct perf_event_context *ctx)
                list_rotate_left(&ctx->flexible_groups);
 }
 
+static void
+perf_calculate_mux_overhead(struct perf_cpu_context *cpuctx, u64 time)
+{
+       cpuctx->mux_overhead.nr++;
+       cpuctx->mux_overhead.time += time;
+}
+
 static int perf_rotate_context(struct perf_cpu_context *cpuctx)
 {
        struct perf_event_context *ctx = NULL;
+       u64 start_clock, end_clock;
        int rotate = 0;
 
        if (cpuctx->ctx.nr_events) {
@@ -3349,6 +3360,7 @@ static int perf_rotate_context(struct perf_cpu_context 
*cpuctx)
        if (!rotate)
                goto done;
 
+       start_clock = perf_clock();
        perf_ctx_lock(cpuctx, cpuctx->task_ctx);
        perf_pmu_disable(cpuctx->ctx.pmu);
 
@@ -3364,6 +3376,8 @@ static int perf_rotate_context(struct perf_cpu_context 
*cpuctx)
 
        perf_pmu_enable(cpuctx->ctx.pmu);
        perf_ctx_unlock(cpuctx, cpuctx->task_ctx);
+       end_clock = perf_clock();
+       perf_calculate_mux_overhead(cpuctx, end_clock - start_clock);
 done:
 
        return rotate;
-- 
2.5.5