From 03541f8b69c058162e4cf9675ec9181e6a204d55 Mon Sep 17 00:00:00 2001 From: Paul Mackerras Date: Wed, 14 Oct 2009 16:58:03 +1100 Subject: perf_event: Adjust frequency and unthrottle for non-group-leader events The loop in perf_ctx_adjust_freq checks the frequency of sampling event counters, and adjusts the event interval and unthrottles the event if required, and resets the interrupt count for the event. However, at present it only looks at group leaders. This means that a sampling event that is not a group leader will eventually get throttled, once its interrupt count reaches sysctl_perf_event_sample_rate/HZ --- and that is guaranteed to happen, if the event is active for long enough, since the interrupt count never gets reset. Once it is throttled it never gets unthrottled, so it basically just stops working at that point. This fixes it by making perf_ctx_adjust_freq use ctx->event_list rather than ctx->group_list. The existing spin_lock/spin_unlock around the loop makes it unnecessary to put rcu_read_lock/ rcu_read_unlock around the list_for_each_entry_rcu(). Reported-by: Mark W. Krentel Signed-off-by: Paul Mackerras Cc: Corey Ashford Cc: Peter Zijlstra LKML-Reference: <19157.26731.855609.165622@cargo.ozlabs.ibm.com> Signed-off-by: Ingo Molnar --- kernel/perf_event.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'kernel/perf_event.c') diff --git a/kernel/perf_event.c b/kernel/perf_event.c index 9d0b5c665883..afb7ef3dbc44 100644 --- a/kernel/perf_event.c +++ b/kernel/perf_event.c @@ -1355,7 +1355,7 @@ static void perf_ctx_adjust_freq(struct perf_event_context *ctx) u64 interrupts, freq; spin_lock(&ctx->lock); - list_for_each_entry(event, &ctx->group_list, group_entry) { + list_for_each_entry_rcu(event, &ctx->event_list, event_entry) { if (event->state != PERF_EVENT_STATE_ACTIVE) continue; -- cgit v1.2.2 From 721a669b7225edeeb0ca8e2bf71b83882326a71b Mon Sep 17 00:00:00 2001 From: Soeren Sandmann Date: Tue, 15 Sep 2009 14:33:08 +0200 Subject: perf events: Fix swevent hrtimer sampling by keeping track of remaining time when enabling/disabling swevent hrtimers MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Make the hrtimer based events work for sysprof. Whenever a swevent is scheduled out, the hrtimer is canceled. When it is scheduled back in, the timer is restarted. This happens every scheduler tick, which means the timer never expired because it was getting repeatedly restarted over and over with the same period. To fix that, save the remaining time when disabling; when reenabling, use that saved time as the period instead of the user-specified sampling period. Also, move the starting and stopping of the hrtimers to helper functions instead of duplicating the code. Signed-off-by: Søren Sandmann Pedersen LKML-Reference: Signed-off-by: Ingo Molnar --- kernel/perf_event.c | 61 +++++++++++++++++++++++++++++++++++------------------ 1 file changed, 41 insertions(+), 20 deletions(-) (limited to 'kernel/perf_event.c') diff --git a/kernel/perf_event.c b/kernel/perf_event.c index afb7ef3dbc44..33ff019f9aa6 100644 --- a/kernel/perf_event.c +++ b/kernel/perf_event.c @@ -3969,6 +3969,42 @@ static enum hrtimer_restart perf_swevent_hrtimer(struct hrtimer *hrtimer) return ret; } +static void perf_swevent_start_hrtimer(struct perf_event *event) +{ + struct hw_perf_event *hwc = &event->hw; + + hrtimer_init(&hwc->hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); + hwc->hrtimer.function = perf_swevent_hrtimer; + if (hwc->sample_period) { + u64 period; + + if (hwc->remaining) { + if (hwc->remaining < 0) + period = 10000; + else + period = hwc->remaining; + hwc->remaining = 0; + } else { + period = max_t(u64, 10000, hwc->sample_period); + } + __hrtimer_start_range_ns(&hwc->hrtimer, + ns_to_ktime(period), 0, + HRTIMER_MODE_REL, 0); + } +} + +static void perf_swevent_cancel_hrtimer(struct perf_event *event) +{ + struct hw_perf_event *hwc = &event->hw; + + if (hwc->sample_period) { + ktime_t remaining = hrtimer_get_remaining(&hwc->hrtimer); + hwc->remaining = ktime_to_ns(remaining); + + hrtimer_cancel(&hwc->hrtimer); + } +} + /* * Software event: cpu wall time clock */ @@ -3991,22 +4027,14 @@ static int cpu_clock_perf_event_enable(struct perf_event *event) int cpu = raw_smp_processor_id(); atomic64_set(&hwc->prev_count, cpu_clock(cpu)); - hrtimer_init(&hwc->hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); - hwc->hrtimer.function = perf_swevent_hrtimer; - if (hwc->sample_period) { - u64 period = max_t(u64, 10000, hwc->sample_period); - __hrtimer_start_range_ns(&hwc->hrtimer, - ns_to_ktime(period), 0, - HRTIMER_MODE_REL, 0); - } + perf_swevent_start_hrtimer(event); return 0; } static void cpu_clock_perf_event_disable(struct perf_event *event) { - if (event->hw.sample_period) - hrtimer_cancel(&event->hw.hrtimer); + perf_swevent_cancel_hrtimer(event); cpu_clock_perf_event_update(event); } @@ -4043,22 +4071,15 @@ static int task_clock_perf_event_enable(struct perf_event *event) now = event->ctx->time; atomic64_set(&hwc->prev_count, now); - hrtimer_init(&hwc->hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); - hwc->hrtimer.function = perf_swevent_hrtimer; - if (hwc->sample_period) { - u64 period = max_t(u64, 10000, hwc->sample_period); - __hrtimer_start_range_ns(&hwc->hrtimer, - ns_to_ktime(period), 0, - HRTIMER_MODE_REL, 0); - } + + perf_swevent_start_hrtimer(event); return 0; } static void task_clock_perf_event_disable(struct perf_event *event) { - if (event->hw.sample_period) - hrtimer_cancel(&event->hw.hrtimer); + perf_swevent_cancel_hrtimer(event); task_clock_perf_event_update(event, event->ctx->time); } -- cgit v1.2.2 From 54f4407608c59712a8f5ec1e10dfac40bef5a2e7 Mon Sep 17 00:00:00 2001 From: Soeren Sandmann Date: Thu, 22 Oct 2009 18:34:08 +0200 Subject: perf events: Don't generate events for the idle task when exclude_idle is set MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Getting samples for the idle task is often not interesting, so don't generate them when exclude_idle is set for the event in question. Signed-off-by: Søren Sandmann Pedersen Cc: Peter Zijlstra Cc: Mike Galbraith Cc: Paul Mackerras Cc: Arnaldo Carvalho de Melo Cc: Frederic Weisbecker Cc: Steven Rostedt LKML-Reference: Signed-off-by: Ingo Molnar --- kernel/perf_event.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) (limited to 'kernel/perf_event.c') diff --git a/kernel/perf_event.c b/kernel/perf_event.c index 33ff019f9aa6..7f29643c8985 100644 --- a/kernel/perf_event.c +++ b/kernel/perf_event.c @@ -3959,8 +3959,9 @@ static enum hrtimer_restart perf_swevent_hrtimer(struct hrtimer *hrtimer) regs = task_pt_regs(current); if (regs) { - if (perf_event_overflow(event, 0, &data, regs)) - ret = HRTIMER_NORESTART; + if (!(event->attr.exclude_idle && current->pid == 0)) + if (perf_event_overflow(event, 0, &data, regs)) + ret = HRTIMER_NORESTART; } period = max_t(u64, 10000, event->hw.sample_period); -- cgit v1.2.2