perf_counter: Accurate period data

We currently log hw.sample_period for PERF_SAMPLE_PERIOD, however this is
incorrect. When we adjust the period, it will only take effect the next
cycle but report it for the current cycle. So when we adjust the period
for every cycle, we're always wrong.

Solve this by keeping track of the last_period.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: 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>

1 files changed, 4 insertions, 2 deletions

diff --git a/include/linux/perf_counter.h b/include/linux/perf_counter.h
index d8c0eb480f9a..5b966472b458 100644
--- a/include/linux/perf_counter.h
+++ b/include/linux/perf_counter.h
@@ -366,6 +366,7 @@ struct hw_perf_counter {
         };
         atomic64_t                      prev_count;
         u64                             sample_period;
+        u64                             last_period;
         atomic64_t                      period_left;
         u64                             interrupts;
 
@@ -606,8 +607,9 @@ extern int hw_perf_group_sched_in(struct perf_counter *group_leader,
 extern void perf_counter_update_userpage(struct perf_counter *counter);
 
 struct perf_sample_data {
-        struct pt_regs  *regs;
-        u64             addr;
+        struct pt_regs          *regs;
+        u64                     addr;
+        u64                     period;
 };
 
 extern int perf_counter_overflow(struct perf_counter *counter, int nmi,