From: Kan Liang <[email protected]> Iterating all events which need to receive side-band events also bring some overhead. Save the overhead information in task context or CPU context, whichever context is available.
Signed-off-by: Kan Liang <[email protected]> --- include/linux/perf_event.h | 2 ++ include/uapi/linux/perf_event.h | 1 + kernel/events/core.c | 32 ++++++++++++++++++++++++++++---- 3 files changed, 31 insertions(+), 4 deletions(-) diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index f72b97a..ec3cb7f 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -764,6 +764,8 @@ struct perf_event_context { #endif void *task_ctx_data; /* pmu specific data */ struct rcu_head rcu_head; + + struct perf_overhead_entry sb_overhead; }; /* diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h index 9124c7c..5e7c522 100644 --- a/include/uapi/linux/perf_event.h +++ b/include/uapi/linux/perf_event.h @@ -994,6 +994,7 @@ struct perf_branch_entry { enum perf_record_overhead_type { PERF_NMI_OVERHEAD = 0, PERF_MUX_OVERHEAD, + PERF_SB_OVERHEAD, PERF_OVERHEAD_MAX, }; diff --git a/kernel/events/core.c b/kernel/events/core.c index 9934059..51e9df7 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -1829,9 +1829,15 @@ event_sched_out(struct perf_event *event, if (event->attr.exclusive || !cpuctx->active_oncpu) cpuctx->exclusive = 0; - if (log_overhead && cpuctx->mux_overhead.nr) { - cpuctx->mux_overhead.cpu = smp_processor_id(); - perf_log_overhead(event, PERF_MUX_OVERHEAD, &cpuctx->mux_overhead); + if (log_overhead) { + if (cpuctx->mux_overhead.nr) { + cpuctx->mux_overhead.cpu = smp_processor_id(); + perf_log_overhead(event, PERF_MUX_OVERHEAD, &cpuctx->mux_overhead); + } + if (ctx->sb_overhead.nr) { + ctx->sb_overhead.cpu = smp_processor_id(); + perf_log_overhead(event, PERF_SB_OVERHEAD, &ctx->sb_overhead); + } } perf_pmu_enable(event->pmu); @@ -6133,6 +6139,14 @@ static void perf_iterate_sb_cpu(perf_iterate_f output, void *data) } } +static void +perf_caculate_sb_overhead(struct perf_event_context *ctx, + u64 time) +{ + ctx->sb_overhead.nr++; + ctx->sb_overhead.time += time; +} + /* * Iterate all events that need to receive side-band events. * @@ -6143,9 +6157,12 @@ static void perf_iterate_sb(perf_iterate_f output, void *data, struct perf_event_context *task_ctx) { + struct perf_event_context *overhead_ctx = task_ctx; struct perf_event_context *ctx; + u64 start_clock, end_clock; int ctxn; + start_clock = perf_clock(); rcu_read_lock(); preempt_disable(); @@ -6163,12 +6180,19 @@ perf_iterate_sb(perf_iterate_f output, void *data, for_each_task_context_nr(ctxn) { ctx = rcu_dereference(current->perf_event_ctxp[ctxn]); - if (ctx) + if (ctx) { perf_iterate_ctx(ctx, output, data, false); + if (!overhead_ctx) + overhead_ctx = ctx; + } } done: preempt_enable(); rcu_read_unlock(); + + end_clock = perf_clock(); + if (overhead_ctx) + perf_caculate_sb_overhead(overhead_ctx, end_clock - start_clock); } /* -- 2.5.5
