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authorRobert Richter <robert.richter@amd.com>2012-04-02 20:19:14 +0200
committerIngo Molnar <mingo@kernel.org>2012-05-09 15:23:15 +0200
commitfc006cf7cc7471e1bdf34e40111971e03622af6c (patch)
tree02845a28bbbddb255d3e2c09b281d7f1f1213563
parent98112d2e957e0d348f06d8a40f2f720204a70b55 (diff)
downloadop-kernel-dev-fc006cf7cc7471e1bdf34e40111971e03622af6c.zip
op-kernel-dev-fc006cf7cc7471e1bdf34e40111971e03622af6c.tar.gz
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@amd.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Link: http://lkml.kernel.org/r/1333390758-10893-9-git-send-email-robert.richter@amd.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
-rw-r--r--arch/x86/kernel/cpu/perf_event_amd_ibs.c5
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;
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