diff options
Diffstat (limited to 'arch/arm/kernel/perf_event.c')
| -rw-r--r-- | arch/arm/kernel/perf_event.c | 22 |
1 files changed, 11 insertions, 11 deletions
diff --git a/arch/arm/kernel/perf_event.c b/arch/arm/kernel/perf_event.c index 5bb91bf3d47f..56173ae16448 100644 --- a/arch/arm/kernel/perf_event.c +++ b/arch/arm/kernel/perf_event.c @@ -180,7 +180,7 @@ armpmu_event_set_period(struct perf_event *event, u64 armpmu_event_update(struct perf_event *event, struct hw_perf_event *hwc, - int idx, int overflow) + int idx) { struct arm_pmu *armpmu = to_arm_pmu(event->pmu); u64 delta, prev_raw_count, new_raw_count; @@ -193,13 +193,7 @@ again: new_raw_count) != prev_raw_count) goto again; - new_raw_count &= armpmu->max_period; - prev_raw_count &= armpmu->max_period; - - if (overflow) - delta = armpmu->max_period - prev_raw_count + new_raw_count + 1; - else - delta = new_raw_count - prev_raw_count; + delta = (new_raw_count - prev_raw_count) & armpmu->max_period; local64_add(delta, &event->count); local64_sub(delta, &hwc->period_left); @@ -216,7 +210,7 @@ armpmu_read(struct perf_event *event) if (hwc->idx < 0) return; - armpmu_event_update(event, hwc, hwc->idx, 0); + armpmu_event_update(event, hwc, hwc->idx); } static void @@ -232,7 +226,7 @@ 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, 0); + armpmu_event_update(event, hwc, hwc->idx); hwc->state |= PERF_HES_STOPPED | PERF_HES_UPTODATE; } } @@ -518,7 +512,13 @@ __hw_perf_event_init(struct perf_event *event) hwc->config_base |= (unsigned long)mapping; if (!hwc->sample_period) { - hwc->sample_period = armpmu->max_period; + /* + * For non-sampling runs, limit the sample_period to half + * of the counter width. That way, the new counter value + * is far less likely to overtake the previous one unless + * you have some serious IRQ latency issues. + */ + hwc->sample_period = armpmu->max_period >> 1; hwc->last_period = hwc->sample_period; local64_set(&hwc->period_left, hwc->sample_period); } |