perf/x86-ibs: Extend hw period that triggers overflow (7caaf4d8) · Commits · e / devices / android_kernel_fairphone_FP5

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:

Robert Richter <robert.richter@amd.com> Signed-off-by:

Peter Zijlstra <a.p.zijlstra@chello.nl> Link: http://lkml.kernel.org/r/1333390758-10893-10-git-send-email-robert.richter@amd.com Signed-off-by:

Ingo Molnar <mingo@kernel.org>

arch/x86/kernel/cpu/perf_event_amd_ibs.c

+13 −2

Original line number	Original line	Diff line number	Diff line
	@@ -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 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)		if (left > max)
	left = max;		left = max;
			else if (left < min)
			left = min;
			}

	*hw_period = (u64)left;		*hw_period = (u64)left;