perf_counter: PERF_RECORD_TIME

By popular request, provide means to log a timestamp along with the
counter overflow event.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
LKML-Reference: <20090406094518.024173282@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 14 insertions, 0 deletions

diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index c841563de043..19990d1f0215 100644
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -1826,6 +1826,7 @@ static void perf_counter_output(struct perf_counter *counter,
         } group_entry;
         struct perf_callchain_entry *callchain = NULL;
         int callchain_size = 0;
+        u64 time;
 
         header.type = PERF_EVENT_COUNTER_OVERFLOW;
         header.size = sizeof(header);
@@ -1862,6 +1863,16 @@ static void perf_counter_output(struct perf_counter *counter,
                 }
         }
 
+        if (record_type & PERF_RECORD_TIME) {
+                /*
+                 * Maybe do better on x86 and provide cpu_clock_nmi()
+                 */
+                time = sched_clock();
+
+                header.type |= __PERF_EVENT_TIME;
+                header.size += sizeof(u64);
+        }
+
         ret = perf_output_begin(&handle, counter, header.size, nmi);
         if (ret)
                 return;
@@ -1895,6 +1906,9 @@ static void perf_counter_output(struct perf_counter *counter,
         if (callchain)
                 perf_output_copy(&handle, callchain, callchain_size);
 
+        if (record_type & PERF_RECORD_TIME)
+                perf_output_put(&handle, time);
+
         perf_output_end(&handle);
 }