perf sched: Add max delay time snapshot

When we have a maximum latency reported for a task, we need a
convenient way to find the matching location to the raw traces
or to perf sched map that shows where the task has been
eventually scheduled in. This gives a pointer to retrieve the
events that occured during this max latency.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Reviewed-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
LKML-Reference: <1260391208-6808-1-git-send-regression-fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

tools/perf/builtin-sched.c

@@ -140,6 +140,7 @@ struct work_atoms {
 	struct thread		*thread;
 	struct rb_node		node;
 	u64			max_lat;
+	u64			max_lat_at;
 	u64			total_lat;
 	u64			nb_atoms;
 	u64			total_runtime;
@@ -1013,8 +1014,10 @@ add_sched_in_event(struct work_atoms *atoms, u64 timestamp)
 
 	delta = atom->sched_in_time - atom->wake_up_time;
 	atoms->total_lat += delta;
-	if (delta > atoms->max_lat)
+	if (delta > atoms->max_lat) {
 		atoms->max_lat = delta;
+		atoms->max_lat_at = timestamp;
+	}
 	atoms->nb_atoms++;
 }
 
@@ -1210,10 +1213,11 @@ static void output_lat_thread(struct work_atoms *work_list)
 
 	avg = work_list->total_lat / work_list->nb_atoms;
 
-	printf("|%11.3f ms |%9llu | avg:%9.3f ms | max:%9.3f ms |\n",
+	printf("|%11.3f ms |%9llu | avg:%9.3f ms | max:%9.3f ms | max at: %9.6f s\n",
 	      (double)work_list->total_runtime / 1e6,
 		 work_list->nb_atoms, (double)avg / 1e6,
-		 (double)work_list->max_lat / 1e6);
+		 (double)work_list->max_lat / 1e6,
+		 (double)work_list->max_lat_at / 1e9);
 }
 
 static int pid_cmp(struct work_atoms *l, struct work_atoms *r)
@@ -1704,9 +1708,9 @@ static void __cmd_lat(void)
 	read_events();
 	sort_lat();
 
-	printf("\n -----------------------------------------------------------------------------------------\n");
-	printf("  Task                  |   Runtime ms  | Switches | Average delay ms | Maximum delay ms |\n");
-	printf(" -----------------------------------------------------------------------------------------\n");
+	printf("\n ---------------------------------------------------------------------------------------------------------------\n");
+	printf("  Task                  |   Runtime ms  | Switches | Average delay ms | Maximum delay ms | Maximum delay at     |\n");
+	printf(" ---------------------------------------------------------------------------------------------------------------\n");
 
 	next = rb_first(&sorted_atom_root);