From 3d1309855c533a39203a8feec95c6b7d51a76bc3 Mon Sep 17 00:00:00 2001
From: Timo Kokkonen <kaapeli@ee.oulu.fi>
Date: Thu, 15 May 2008 20:10:18 +0300
Subject: [PATCH] Add support for latency measuring

---
 membench.c | 62 +++++++++++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 54 insertions(+), 8 deletions(-)

diff --git a/membench.c b/membench.c
index 7cad40b..53b967b 100644
--- a/membench.c
+++ b/membench.c
@@ -14,7 +14,7 @@ long usec_diff(const struct timeval *a, const struct timeval *b)
 
 int main(int argc, char *argv[])
 {
-	int iterations, j, k, count, size;
+	int iterations, j, k, count, size, mask, latcount;
 	unsigned long *buf, i, tmp = 0;
 	struct timeval start, end;
 
@@ -24,14 +24,15 @@ int main(int argc, char *argv[])
 		iterations = 24;
 
 	if (argc > 2)
-		count = atoi(argv[2]) * 1024;
+		count = atoi(argv[2]);
 	else
 		count = 1024;
+	latcount = count / 10;
 
 	printf("Doing %d runs with buffer size goin up to %dk\n",
 	       iterations, 1 << (iterations - 10));
 	printf("Running each round %d times\n", count);
-	printf("Size of unsigned long is %lu bits\n", lsize * 8);
+	printf("Size of unsigned long is %lu bits\n\n", lsize * 8);
 
 	switch (lsize) {
 	case 4:
@@ -45,9 +46,24 @@ int main(int argc, char *argv[])
 		exit(1);
 	}
 
+	printf("          |"
+	       "         Read         |"
+	       "         Write        |\n"
+	       "          |"
+	       "-----------------------"
+	       "-----------------------\n"
+	       "    Size  |"
+	       "    MiB/s         ns  |"
+	       "    MiB/s         ns  |\n"
+	       "----------|"
+	       "-----------------------"
+	       "-----------------------\n"
+		);
+
 	for (; j < iterations + 1; j++) {
 		size = (1 << j) / lsize;
 		buf = malloc(size * lsize);
+		mask = size - 1;
 
 		if (buf == NULL) {
 			printf("Malloc failed\n");
@@ -58,9 +74,10 @@ int main(int argc, char *argv[])
 		for (i = 0; i < size; i++)
 			buf[i] = i;
 
-		printf("%luk\t", size * lsize / 1024);
+		printf("%8luk |", size * lsize / 1024);
+
+		/* Read bandwidth*/
 
-		printf("read: ");
 		fflush(stdout);
 
 		gettimeofday(&start, 0);
@@ -72,24 +89,53 @@ int main(int argc, char *argv[])
 
 		gettimeofday(&end, 0);
 
-		printf("% 9.2f MB/s ", (double)(size * lsize) * 
+		printf("% 9.2f  ", (double)(size * lsize) * 
 		       (1000000 / (1024.0 * 1024.0)) * count / 
 		       (double) usec_diff(&start, &end));
 
+		fflush(stdout);
+
+		/* Read latency */
+
+		gettimeofday(&start, 0);
+		for (k = 0; k < latcount; k++) {
+			buf[0] = tmp;
+			for (i = 0; i < size; i++)
+				tmp += buf[random() & mask];
+		}
+
+		gettimeofday(&end, 0);
+
+		printf("% 9.3f  |", usec_diff(&start, &end) * 1000 / 
+		       ((double) (size * latcount )));
+
 
-		printf("write: ");
 		fflush(stdout);
 
+		/* Write bandwidth */
+
 		gettimeofday(&start, 0);
 		for (k = 0; k < count; k++)
 			for (i = 0; i < size; i++)
 				 buf[i] = i;
 		gettimeofday(&end, 0);
 
-		printf("% 9.2f MB/s ", (double)(size * lsize) * 
+		printf("% 9.2f  ", (double)(size * lsize) * 
 		       (1000000 / (1024.0 * 1024.0)) * count / 
 		       (double) usec_diff(&start, &end));
 	
+
+		/* Write latency */
+
+		gettimeofday(&start, 0);
+		for (k = 0; k < latcount; k++)
+			for (i = 0; i < size; i++)
+				buf[random() % mask] = i;
+		gettimeofday(&end, 0);
+
+		printf("% 9.3f  |", usec_diff(&start, &end) * 1000 / 
+		       ((double) (size * latcount )));
+	
 		printf("\n");
 
 		free(buf);
-- 
2.44.0