From d76a0812ac4139ceb54daab3cc70e1bd8bd9d43a Mon Sep 17 00:00:00 2001 From: Stephane Eranian Date: Mon, 8 Feb 2010 17:06:01 +0200 Subject: perf_events: Add new start/stop PMU callbacks In certain situations, the kernel may need to stop and start the same event rapidly. The current PMU callbacks do not distinguish between stop and release (i.e., stop + free the resource). Thus, a counter may be released, then it will be immediately re-acquired. Event scheduling will again take place with no guarantee to assign the same counter. On some processors, this may event yield to failure to assign the event back due to competion between cores. This patch is adding a new pair of callback to stop and restart a counter without actually release the underlying counter resource. On stop, the counter is stopped, its values saved and that's it. On start, the value is reloaded and counter is restarted (on x86, actual restart is delayed until perf_enable()). Signed-off-by: Stephane Eranian [ added fallback to ->enable/->disable for all other PMUs fixed x86_pmu_start() to call x86_pmu.enable() merged __x86_pmu_disable into x86_pmu_stop() ] Signed-off-by: Peter Zijlstra LKML-Reference: <4b703875.0a04d00a.7896.ffffb824@mx.google.com> Signed-off-by: Ingo Molnar --- kernel/perf_event.c | 20 ++++++++++++++++++-- 1 file changed, 18 insertions(+), 2 deletions(-) (limited to 'kernel') diff --git a/kernel/perf_event.c b/kernel/perf_event.c index 5a69abb05ac3..74c60021cdbc 100644 --- a/kernel/perf_event.c +++ b/kernel/perf_event.c @@ -1493,6 +1493,22 @@ do { \ return div64_u64(dividend, divisor); } +static void perf_event_stop(struct perf_event *event) +{ + if (!event->pmu->stop) + return event->pmu->disable(event); + + return event->pmu->stop(event); +} + +static int perf_event_start(struct perf_event *event) +{ + if (!event->pmu->start) + return event->pmu->enable(event); + + return event->pmu->start(event); +} + static void perf_adjust_period(struct perf_event *event, u64 nsec, u64 count) { struct hw_perf_event *hwc = &event->hw; @@ -1513,9 +1529,9 @@ static void perf_adjust_period(struct perf_event *event, u64 nsec, u64 count) if (atomic64_read(&hwc->period_left) > 8*sample_period) { perf_disable(); - event->pmu->disable(event); + perf_event_stop(event); atomic64_set(&hwc->period_left, 0); - event->pmu->enable(event); + perf_event_start(event); perf_enable(); } } -- cgit v1.2.3