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| author | Robert Richter | 2012-04-02 20:19:15 +0200 |
|---|---|---|
| committer | Ingo Molnar | 2012-05-09 15:23:15 +0200 |
| commit | 7caaf4d8241feecafb87919402b0a6dbb1b71d9e (patch) | |
| tree | 010358e8d67b75dc11ba27221e221500ad0e4882 /arch/x86/kernel/cpu/perf_event_amd_ibs.c | |
| parent | perf/x86-ibs: Trigger overflow if remaining period is too small (diff) | |
| download | kernel-qcow2-linux-7caaf4d8241feecafb87919402b0a6dbb1b71d9e.tar.gz kernel-qcow2-linux-7caaf4d8241feecafb87919402b0a6dbb1b71d9e.tar.xz kernel-qcow2-linux-7caaf4d8241feecafb87919402b0a6dbb1b71d9e.zip | |
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: 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>
Diffstat (limited to 'arch/x86/kernel/cpu/perf_event_amd_ibs.c')
| -rw-r--r-- | arch/x86/kernel/cpu/perf_event_amd_ibs.c | 15 |
1 files changed, 13 insertions, 2 deletions
diff --git a/arch/x86/kernel/cpu/perf_event_amd_ibs.c b/arch/x86/kernel/cpu/perf_event_amd_ibs.c index 3e32908292a7..cb51a3e55870 100644 --- a/arch/x86/kernel/cpu/perf_event_amd_ibs.c +++ b/arch/x86/kernel/cpu/perf_event_amd_ibs.c @@ -85,8 +85,19 @@ perf_event_set_period(struct hw_perf_event *hwc, u64 min, u64 max, u64 *hw_perio 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; |