Commit-ID: fc006cf7cc7471e1bdf34e40111971e03622af6c Gitweb: http://git.kernel.org/tip/fc006cf7cc7471e1bdf34e40111971e03622af6c Author: Robert Richter <robert.richter@xxxxxxx> AuthorDate: Mon, 2 Apr 2012 20:19:14 +0200 Committer: Ingo Molnar <mingo@xxxxxxxxxx> CommitDate: Wed, 9 May 2012 15:23:15 +0200 perf/x86-ibs: Trigger overflow if remaining period is too small There are cases where the remaining period is smaller than the minimal possible value. In this case the counter is restarted with the minimal period. This is of no use as the interrupt handler will trigger immediately again and most likely hits itself. This biases the results. So, if the remaining period is within the min range, we better do not restart the counter and instead trigger the overflow. Signed-off-by: Robert Richter <robert.richter@xxxxxxx> Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx> Link: http://lkml.kernel.org/r/1333390758-10893-9-git-send-email-robert.richter@xxxxxxx Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> --- arch/x86/kernel/cpu/perf_event_amd_ibs.c | 5 +---- 1 files changed, 1 insertions(+), 4 deletions(-) diff --git a/arch/x86/kernel/cpu/perf_event_amd_ibs.c b/arch/x86/kernel/cpu/perf_event_amd_ibs.c index 29a1bff..3e32908 100644 --- a/arch/x86/kernel/cpu/perf_event_amd_ibs.c +++ b/arch/x86/kernel/cpu/perf_event_amd_ibs.c @@ -78,16 +78,13 @@ perf_event_set_period(struct hw_perf_event *hwc, u64 min, u64 max, u64 *hw_perio overflow = 1; } - if (unlikely(left <= 0)) { + if (unlikely(left < (s64)min)) { left += period; local64_set(&hwc->period_left, left); hwc->last_period = period; overflow = 1; } - if (unlikely(left < min)) - left = min; - if (left > max) left = max; -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html