diff options
author | Will Deacon <will.deacon@arm.com> | 2011-03-25 17:12:37 +0100 |
---|---|---|
committer | Russell King <rmk+kernel@arm.linux.org.uk> | 2011-03-26 11:06:09 +0100 |
commit | a737823d37666255e3e74ce84bc9611a038e0888 (patch) | |
tree | 0424691dc1af593e08877cb1ee2b2e59334f532f | |
parent | ARM: 6834/1: perf: reset counters on all CPUs during initialisation (diff) | |
download | linux-a737823d37666255e3e74ce84bc9611a038e0888.tar.xz linux-a737823d37666255e3e74ce84bc9611a038e0888.zip |
ARM: 6835/1: perf: ensure overflows aren't missed due to IRQ latency
If a counter overflows during a perf stat profiling run it may overtake
the last known value of the counter:
0 prev new 0xffffffff
|----------|-------|----------------------|
In this case, the number of events that have occurred is
(0xffffffff - prev) + new. Unfortunately, the event update code will
not realise an overflow has occurred and will instead report the event
delta as (new - prev) which may be considerably smaller than the real
count.
This patch adds an extra argument to armpmu_event_update which indicates
whether or not an overflow has occurred. If an overflow has occurred
then we use the maximum period of the counter to calculate the elapsed
events.
Acked-by: Jamie Iles <jamie@jamieiles.com>
Reported-by: Ashwin Chaugule <ashwinc@codeaurora.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
-rw-r--r-- | arch/arm/kernel/perf_event.c | 19 | ||||
-rw-r--r-- | arch/arm/kernel/perf_event_v6.c | 2 | ||||
-rw-r--r-- | arch/arm/kernel/perf_event_v7.c | 2 | ||||
-rw-r--r-- | arch/arm/kernel/perf_event_xscale.c | 4 |
4 files changed, 15 insertions, 12 deletions
diff --git a/arch/arm/kernel/perf_event.c b/arch/arm/kernel/perf_event.c index e422f4c269a0..69cfee0fe00f 100644 --- a/arch/arm/kernel/perf_event.c +++ b/arch/arm/kernel/perf_event.c @@ -205,11 +205,9 @@ armpmu_event_set_period(struct perf_event *event, static u64 armpmu_event_update(struct perf_event *event, struct hw_perf_event *hwc, - int idx) + int idx, int overflow) { - int shift = 64 - 32; - s64 prev_raw_count, new_raw_count; - u64 delta; + u64 delta, prev_raw_count, new_raw_count; again: prev_raw_count = local64_read(&hwc->prev_count); @@ -219,8 +217,13 @@ again: new_raw_count) != prev_raw_count) goto again; - delta = (new_raw_count << shift) - (prev_raw_count << shift); - delta >>= shift; + new_raw_count &= armpmu->max_period; + prev_raw_count &= armpmu->max_period; + + if (overflow) + delta = armpmu->max_period - prev_raw_count + new_raw_count; + else + delta = new_raw_count - prev_raw_count; local64_add(delta, &event->count); local64_sub(delta, &hwc->period_left); @@ -237,7 +240,7 @@ armpmu_read(struct perf_event *event) if (hwc->idx < 0) return; - armpmu_event_update(event, hwc, hwc->idx); + armpmu_event_update(event, hwc, hwc->idx, 0); } static void @@ -255,7 +258,7 @@ armpmu_stop(struct perf_event *event, int flags) if (!(hwc->state & PERF_HES_STOPPED)) { armpmu->disable(hwc, hwc->idx); barrier(); /* why? */ - armpmu_event_update(event, hwc, hwc->idx); + armpmu_event_update(event, hwc, hwc->idx, 0); hwc->state |= PERF_HES_STOPPED | PERF_HES_UPTODATE; } } diff --git a/arch/arm/kernel/perf_event_v6.c b/arch/arm/kernel/perf_event_v6.c index 6fc2d228db55..f1e8dd94afe8 100644 --- a/arch/arm/kernel/perf_event_v6.c +++ b/arch/arm/kernel/perf_event_v6.c @@ -474,7 +474,7 @@ armv6pmu_handle_irq(int irq_num, continue; hwc = &event->hw; - armpmu_event_update(event, hwc, idx); + armpmu_event_update(event, hwc, idx, 1); data.period = event->hw.last_period; if (!armpmu_event_set_period(event, hwc, idx)) continue; diff --git a/arch/arm/kernel/perf_event_v7.c b/arch/arm/kernel/perf_event_v7.c index c08d07a99fcc..4960686afb58 100644 --- a/arch/arm/kernel/perf_event_v7.c +++ b/arch/arm/kernel/perf_event_v7.c @@ -782,7 +782,7 @@ static irqreturn_t armv7pmu_handle_irq(int irq_num, void *dev) continue; hwc = &event->hw; - armpmu_event_update(event, hwc, idx); + armpmu_event_update(event, hwc, idx, 1); data.period = event->hw.last_period; if (!armpmu_event_set_period(event, hwc, idx)) continue; diff --git a/arch/arm/kernel/perf_event_xscale.c b/arch/arm/kernel/perf_event_xscale.c index 28cd3b025bc3..39affbe4fdb2 100644 --- a/arch/arm/kernel/perf_event_xscale.c +++ b/arch/arm/kernel/perf_event_xscale.c @@ -246,7 +246,7 @@ xscale1pmu_handle_irq(int irq_num, void *dev) continue; hwc = &event->hw; - armpmu_event_update(event, hwc, idx); + armpmu_event_update(event, hwc, idx, 1); data.period = event->hw.last_period; if (!armpmu_event_set_period(event, hwc, idx)) continue; @@ -578,7 +578,7 @@ xscale2pmu_handle_irq(int irq_num, void *dev) continue; hwc = &event->hw; - armpmu_event_update(event, hwc, idx); + armpmu_event_update(event, hwc, idx, 1); data.period = event->hw.last_period; if (!armpmu_event_set_period(event, hwc, idx)) continue; |