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authorPeter Zijlstra <a.p.zijlstra@chello.nl>2009-06-10 13:40:57 +0200
committerIngo Molnar <mingo@elte.hu>2009-06-10 16:55:26 +0200
commitbd2b5b12849a3446abad0b25e920f86f5480b309 (patch)
treeb0eacf6002f2015c0483390619a3f874bcb7e7d2 /arch/x86
parentdc81081b2d9a6a9d64dad1bef1e5fc9fb660e53e (diff)
perf_counter: More aggressive frequency adjustment
Also employ the overflow handler to adjust the frequency, this results in a stable frequency in about 40~50 samples, instead of that many ticks. This also means we can start sampling at a sample period of 1 without running head-first into the throttle. It relies on sched_clock() to accurately measure the time difference between the overflow NMIs. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Mike Galbraith <efault@gmx.de> Cc: Paul Mackerras <paulus@samba.org> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'arch/x86')
-rw-r--r--arch/x86/kernel/cpu/perf_counter.c5
1 files changed, 3 insertions, 2 deletions
diff --git a/arch/x86/kernel/cpu/perf_counter.c b/arch/x86/kernel/cpu/perf_counter.c
index 49f258537cb..240ca563063 100644
--- a/arch/x86/kernel/cpu/perf_counter.c
+++ b/arch/x86/kernel/cpu/perf_counter.c
@@ -696,10 +696,11 @@ static int __hw_perf_counter_init(struct perf_counter *counter)
if (!attr->exclude_kernel)
hwc->config |= ARCH_PERFMON_EVENTSEL_OS;
- if (!hwc->sample_period)
+ if (!hwc->sample_period) {
hwc->sample_period = x86_pmu.max_period;
+ atomic64_set(&hwc->period_left, hwc->sample_period);
+ }
- atomic64_set(&hwc->period_left, hwc->sample_period);
counter->destroy = hw_perf_counter_destroy;
/*