Messages in this thread Patch in this message | | | From | James Hogan <> | Subject | [PATCH 5/9] metag: perf: fix frequency sampling (dynamic period) | Date | Fri, 15 Mar 2013 13:43:44 +0000 |
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Frequency sampling mode dynamically adjusts the sample period so as to hit a particular frequency of samples. The sample period starts at just 1 and then gets increased if the interrupt rate is too high. This changed sample period needs handling in metag_pmu_event_set_period to update period_left (as the ARM equivalent does). The calculated delta also needs subtracting from period_left in metag_pmu_event_update in order to hit the conditional blocks in metag_pmu_event_set_period which update last_period (which is used in the dynamic sampling period calculation).
Signed-off-by: James Hogan <james.hogan@imgtec.com> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Paul Mackerras <paulus@samba.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net> --- arch/metag/kernel/perf/perf_event.c | 5 +++++ 1 file changed, 5 insertions(+)
diff --git a/arch/metag/kernel/perf/perf_event.c b/arch/metag/kernel/perf/perf_event.c index 5bf984f..6210126 100644 --- a/arch/metag/kernel/perf/perf_event.c +++ b/arch/metag/kernel/perf/perf_event.c @@ -214,6 +214,7 @@ again: delta = (new_raw_count - prev_raw_count) & MAX_PERIOD; local64_add(delta, &event->count); + local64_sub(delta, &hwc->period_left); } int metag_pmu_event_set_period(struct perf_event *event, @@ -223,6 +224,10 @@ int metag_pmu_event_set_period(struct perf_event *event, s64 period = hwc->sample_period; int ret = 0; + /* The period may have been changed */ + if (unlikely(period != hwc->last_period)) + left += period - hwc->last_period; + if (unlikely(left <= -period)) { left = period; local64_set(&hwc->period_left, left); -- 1.8.1.2
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