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>
diff --git a/include/linux/perf_counter.h b/include/linux/perf_counter.h
index 3586df8..282d8cc 100644
--- a/include/linux/perf_counter.h
+++ b/include/linux/perf_counter.h
@@ -371,6 +371,7 @@
u64 freq_count;
u64 freq_interrupts;
+ u64 freq_stamp;
#endif
};