linux-kernel - [BUGFIX] perf record: remove unneeded gettimeofday() call

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Message-ID: <20100518225240.GC25589@sgi.com>
Date:	Tue, 18 May 2010 17:52:40 -0500
From:	Russ Anderson <rja@....com>
To:	Ingo Molnar <mingo@...e.hu>, Peter Zijlstra <peterz@...radead.org>
Cc:	linux-kernel@...r.kernel.org,
	Stephane Eranian <eranian@...gle.com>,
	Russ Anderson <rja@....com>
Subject: [BUGFIX] perf record: remove unneeded gettimeofday() call

Perf record repeatedly calls gettimeofday() which adds noise to the performance 
measurements.  Since gettimeofday() is only used for the error printf,
delete it.

Signed-off-by: Russ Anderson <rja@....com>

---
 tools/perf/builtin-record.c |   17 +----------------
 1 file changed, 1 insertion(+), 16 deletions(-)

Index: linux/tools/perf/builtin-record.c
===================================================================
--- linux.orig/tools/perf/builtin-record.c	2010-05-18 16:03:58.000000000 -0500
+++ linux/tools/perf/builtin-record.c	2010-05-18 17:28:00.765537656 -0500
@@ -64,9 +64,6 @@ static bool			multiplex			=  false;
 static int			multiplex_fd			=     -1;
 
 static long			samples				=      0;
-static struct timeval		last_read;
-static struct timeval		this_read;
-
 static u64			bytes_written			=      0;
 
 static struct pollfd		*event_array;
@@ -146,8 +143,6 @@ static void mmap_read(struct mmap_data *
 	void *buf;
 	int diff;
 
-	gettimeofday(&this_read, NULL);
-
 	/*
 	 * If we're further behind than half the buffer, there's a chance
 	 * the writer will bite our tail and mess up the samples under us.
@@ -158,23 +153,13 @@ static void mmap_read(struct mmap_data *
 	 */
 	diff = head - old;
 	if (diff < 0) {
-		struct timeval iv;
-		unsigned long msecs;
-
-		timersub(&this_read, &last_read, &iv);
-		msecs = iv.tv_sec*1000 + iv.tv_usec/1000;
-
-		fprintf(stderr, "WARNING: failed to keep up with mmap data."
-				"  Last read %lu msecs ago.\n", msecs);
-
+		fprintf(stderr, "WARNING: failed to keep up with mmap data\n");
 		/*
 		 * head points to a known good entry, start there.
 		 */
 		old = head;
 	}
 
-	last_read = this_read;
-
 	if (old != head)
 		samples++;
 
-- 
Russ Anderson, OS RAS/Partitioning Project Lead  
SGI - Silicon Graphics Inc          rja@....com
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