On Mon, Apr 16, 2018 at 10:04:53PM +0000, Stephane Eranian wrote: > Hi, > > I am trying to understand what the exclude_idle event attribute is supposed > to accomplish. > As per the definition in the header file: > > exclude_idle : 1, /* don't count when idle */ > > Naively, I thought it would simply stop the event when running in the > context of the idle task (swapper, pid 0) on any CPU. That would seem to > match the succinct description. > > However, running a simple: > > $ perf record -a -e cycles:I sleep 5 > perf_event_attr: > sample_type IP|TID|TIME|CPU|PERIOD > read_format TOTAL_TIME_ENABLED|TOTAL_TIME_RUNNING|ID > exclude_idle 1 > > on an idle machine, showed me that this is not what is actually happening: > $ perf script > swapper 0 [000] 1132634.287442: 1 cycles:I: > ffffffff8100b1fb __intel_pmu_enable_all.isra.17 ([kernel.kallsyms]) > swapper 0 [001] 1132634.287498: 1 cycles:I: > ffffffff8100b1fb __intel_pmu_enable_all.isra.17 ([kernel.kallsyms]) > > > After looking at the code, it all made sense, it seems to current > implementation is only relevant for sw events. I don't understand why.
AFAICS it's not implemented Peter suggested some time ago change for cpu-clock (attached) I still have it in my queue, because it gives funny numbers sometimes.. and I haven't figured it out so far the idea so far was to use cpu-clock,cpu-clock:I events to count and display idle % in perf top/record and stat metrics jirka --- >From 7f20b047cf56f8086d79007175592633798656ce Mon Sep 17 00:00:00 2001 From: Peter Zijlstra <pet...@infradead.org> Date: Thu, 23 Nov 2017 16:15:36 +0100 Subject: [PATCH] perf: Add support to monitor idle time on cpu-clock Adding support to use perf_event_attr::exclude_idle (the :I modifierr in perf tools)to monitor idle time on cpu-clock event. Link: http://lkml.kernel.org/n/tip-jw45kl6ydrhzqx4uxws0q...@git.kernel.org Signed-off-by: Jiri Olsa <jo...@kernel.org> --- kernel/events/core.c | 22 ++++++++++++++++++---- kernel/sched/idle_task.c | 17 +++++++++++++++++ 2 files changed, 35 insertions(+), 4 deletions(-) diff --git a/kernel/events/core.c b/kernel/events/core.c index 2989e3b0fe8b..62c0dc75ed11 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -9391,19 +9391,33 @@ static void perf_swevent_init_hrtimer(struct perf_event *event) * Software event: cpu wall time clock */ +static u64 cpu_clock_count(struct perf_event *event) +{ + u64 now = local_clock(); + + if (event->attr.exclude_idle) + now -= idle_task(event->oncpu)->se.sum_exec_runtime; + + return now; +} + static void cpu_clock_event_update(struct perf_event *event) { - s64 prev; + s64 prev, delta; u64 now; - now = local_clock(); + now = cpu_clock_count(event); prev = local64_xchg(&event->hw.prev_count, now); - local64_add(now - prev, &event->count); + delta = now - prev; + if (delta > 0) + local64_add(delta, &event->count); } static void cpu_clock_event_start(struct perf_event *event, int flags) { - local64_set(&event->hw.prev_count, local_clock()); + u64 now = cpu_clock_count(event); + + local64_set(&event->hw.prev_count, now); perf_swevent_start_hrtimer(event); } diff --git a/kernel/sched/idle_task.c b/kernel/sched/idle_task.c index d518664cce4f..e360ce5dd9a2 100644 --- a/kernel/sched/idle_task.c +++ b/kernel/sched/idle_task.c @@ -27,9 +27,14 @@ static void check_preempt_curr_idle(struct rq *rq, struct task_struct *p, int fl static struct task_struct * pick_next_task_idle(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) { + struct task_struct *idle = rq->idle; + put_prev_task(rq, prev); update_idle_core(rq); schedstat_inc(rq->sched_goidle); + + idle->se.exec_start = rq_clock_task(rq); + return rq->idle; } @@ -48,6 +53,15 @@ dequeue_task_idle(struct rq *rq, struct task_struct *p, int flags) static void put_prev_task_idle(struct rq *rq, struct task_struct *prev) { + struct task_struct *idle = rq->idle; + u64 delta, now; + + now = rq_clock_task(rq); + delta = now - idle->se.exec_start; + if (likely((s64)delta > 0)) + idle->se.sum_exec_runtime += delta; + idle->se.exec_start = now; + rq_last_tick_reset(rq); } @@ -57,6 +71,9 @@ static void task_tick_idle(struct rq *rq, struct task_struct *curr, int queued) static void set_curr_task_idle(struct rq *rq) { + struct task_struct *idle = rq->idle; + + idle->se.exec_start = rq_clock_task(rq); } static void switched_to_idle(struct rq *rq, struct task_struct *p) -- 2.13.6
