perf_counter: Log irq_period changes

For the dynamic irq_period code, log whenever we change the period so that
analyzing code can normalize the event flow.

[ Impact: add new feature to allow more precise profiling ]

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: John Kacur <jkacur@redhat.com>
LKML-Reference: <20090520102553.298769743@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 8 insertions, 0 deletions

diff --git a/include/linux/perf_counter.h b/include/linux/perf_counter.h
index c8c1dfc22c93..f612941ef46e 100644
--- a/include/linux/perf_counter.h
+++ b/include/linux/perf_counter.h
@@ -258,6 +258,14 @@ enum perf_event_type {
         PERF_EVENT_COMM                 = 3,
 
         /*
+         * struct {
+         *      struct perf_event_header        header;
+         *      u64                             irq_period;
+         * };
+         */
+        PERF_EVENT_PERIOD               = 4,
+
+        /*
          * When header.misc & PERF_EVENT_MISC_OVERFLOW the event_type field
          * will be PERF_RECORD_*
          *