Commit 7caaf4d8 authored by Robert Richter's avatar Robert Richter Committed by Ingo Molnar

perf/x86-ibs: Extend hw period that triggers overflow

If the last hw period is too short we might hit the irq handler which
biases the results. Thus try to have a max last period that triggers
the sw overflow.
Signed-off-by: default avatarRobert Richter <robert.richter@amd.com>
Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1333390758-10893-10-git-send-email-robert.richter@amd.comSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent fc006cf7
...@@ -85,8 +85,19 @@ perf_event_set_period(struct hw_perf_event *hwc, u64 min, u64 max, u64 *hw_perio ...@@ -85,8 +85,19 @@ perf_event_set_period(struct hw_perf_event *hwc, u64 min, u64 max, u64 *hw_perio
overflow = 1; overflow = 1;
} }
if (left > max) /*
left = max; * If the hw period that triggers the sw overflow is too short
* we might hit the irq handler. This biases the results.
* Thus we shorten the next-to-last period and set the last
* period to the max period.
*/
if (left > max) {
left -= max;
if (left > max)
left = max;
else if (left < min)
left = min;
}
*hw_period = (u64)left; *hw_period = (u64)left;
......
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