blktrace: use cpu_clock() instead of sched_clock()

use cpu_clock() instead of sched_clock(). (the latter is not a proper
clock-source)

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

block/blktrace.c

@@ -41,7 +41,7 @@ static void trace_note(struct blk_trace *bt, pid_t pid, int action,
 		const int cpu = smp_processor_id();
 
 		t->magic = BLK_IO_TRACE_MAGIC | BLK_IO_TRACE_VERSION;
-		t->time = sched_clock() - per_cpu(blk_trace_cpu_offset, cpu);
+		t->time = cpu_clock(cpu) - per_cpu(blk_trace_cpu_offset, cpu);
 		t->device = bt->dev;
 		t->action = action;
 		t->pid = pid;
@@ -159,7 +159,7 @@ void __blk_add_trace(struct blk_trace *bt, sector_t sector, int bytes,
 
 		t->magic = BLK_IO_TRACE_MAGIC | BLK_IO_TRACE_VERSION;
 		t->sequence = ++(*sequence);
-		t->time = sched_clock() - per_cpu(blk_trace_cpu_offset, cpu);
+		t->time = cpu_clock(cpu) - per_cpu(blk_trace_cpu_offset, cpu);
 		t->sector = sector;
 		t->bytes = bytes;
 		t->action = what;
@@ -488,17 +488,17 @@ void blk_trace_shutdown(struct request_queue *q)
 }
 
 /*
- * Average offset over two calls to sched_clock() with a gettimeofday()
+ * Average offset over two calls to cpu_clock() with a gettimeofday()
  * in the middle
  */
-static void blk_check_time(unsigned long long *t)
+static void blk_check_time(unsigned long long *t, int this_cpu)
 {
 	unsigned long long a, b;
 	struct timeval tv;
 
-	a = sched_clock();
+	a = cpu_clock(this_cpu);
 	do_gettimeofday(&tv);
-	b = sched_clock();
+	b = cpu_clock(this_cpu);
 
 	*t = tv.tv_sec * 1000000000 + tv.tv_usec * 1000;
 	*t -= (a + b) / 2;
@@ -510,16 +510,16 @@ static void blk_check_time(unsigned long long *t)
 static void blk_trace_check_cpu_time(void *data)
 {
 	unsigned long long *t;
-	int cpu = get_cpu();
+	int this_cpu = get_cpu();
 
-	t = &per_cpu(blk_trace_cpu_offset, cpu);
+	t = &per_cpu(blk_trace_cpu_offset, this_cpu);
 
 	/*
 	 * Just call it twice, hopefully the second call will be cache hot
 	 * and a little more precise
 	 */
-	blk_check_time(t);
-	blk_check_time(t);
+	blk_check_time(t, this_cpu);
+	blk_check_time(t, this_cpu);
 
 	put_cpu();
 }