diff --git a/kernel/dma/map_benchmark.c b/kernel/dma/map_benchmark.c
index e0e64f8..a5c1b01 100644
--- a/kernel/dma/map_benchmark.c
+++ b/kernel/dma/map_benchmark.c
@@ -38,7 +38,8 @@ struct map_benchmark {
 	__u32 dma_bits; /* DMA addressing capability */
 	__u32 dma_dir; /* DMA data direction */
 	__u32 dma_trans_ns; /* time for DMA transmission in ns */
-	__u8 expansion[80];	/* For future use */
+	__u32 granule;	/* how many PAGE_SIZE will do map/unmap once a time */
+	__u8 expansion[76];	/* For future use */
 };
 
 struct map_benchmark_data {
@@ -58,9 +59,11 @@ static int map_benchmark_thread(void *data)
 	void *buf;
 	dma_addr_t dma_addr;
 	struct map_benchmark_data *map = data;
+	int npages = map->bparam.granule;
+	u64 size = npages * PAGE_SIZE;
 	int ret = 0;
 
-	buf = (void *)__get_free_page(GFP_KERNEL);
+	buf = alloc_pages_exact(size, GFP_KERNEL);
 	if (!buf)
 		return -ENOMEM;
 
@@ -76,10 +79,10 @@ static int map_benchmark_thread(void *data)
 		 * 66 means evertything goes well! 66 is lucky.
 		 */
 		if (map->dir != DMA_FROM_DEVICE)
-			memset(buf, 0x66, PAGE_SIZE);
+			memset(buf, 0x66, size);
 
 		map_stime = ktime_get();
-		dma_addr = dma_map_single(map->dev, buf, PAGE_SIZE, map->dir);
+		dma_addr = dma_map_single(map->dev, buf, size, map->dir);
 		if (unlikely(dma_mapping_error(map->dev, dma_addr))) {
 			pr_err("dma_map_single failed on %s\n",
 				dev_name(map->dev));
@@ -93,7 +96,7 @@ static int map_benchmark_thread(void *data)
 		ndelay(map->bparam.dma_trans_ns);
 
 		unmap_stime = ktime_get();
-		dma_unmap_single(map->dev, dma_addr, PAGE_SIZE, map->dir);
+		dma_unmap_single(map->dev, dma_addr, size, map->dir);
 		unmap_etime = ktime_get();
 		unmap_delta = ktime_sub(unmap_etime, unmap_stime);
 
@@ -112,7 +115,7 @@ static int map_benchmark_thread(void *data)
 	}
 
 out:
-	free_page((unsigned long)buf);
+	free_pages_exact(buf, size);
 	return ret;
 }
 
@@ -203,7 +206,6 @@ static long map_benchmark_ioctl(struct file *file, unsigned int cmd,
 	struct map_benchmark_data *map = file->private_data;
 	void __user *argp = (void __user *)arg;
 	u64 old_dma_mask;
-
 	int ret;
 
 	if (copy_from_user(&map->bparam, argp, sizeof(map->bparam)))
@@ -234,6 +236,11 @@ static long map_benchmark_ioctl(struct file *file, unsigned int cmd,
 			return -EINVAL;
 		}
 
+		if (map->bparam.granule < 1 || map->bparam.granule > 1024) {
+			pr_err("invalid granule size\n");
+			return -EINVAL;
+		}
+
 		switch (map->bparam.dma_dir) {
 		case DMA_MAP_BIDIRECTIONAL:
 			map->dir = DMA_BIDIRECTIONAL;
diff --git a/tools/testing/selftests/dma/dma_map_benchmark.c b/tools/testing/selftests/dma/dma_map_benchmark.c
index fb23ce9..6f2caa6 100644
--- a/tools/testing/selftests/dma/dma_map_benchmark.c
+++ b/tools/testing/selftests/dma/dma_map_benchmark.c
@@ -40,7 +40,8 @@ struct map_benchmark {
 	__u32 dma_bits; /* DMA addressing capability */
 	__u32 dma_dir; /* DMA data direction */
 	__u32 dma_trans_ns; /* time for DMA transmission in ns */
-	__u8 expansion[80];	/* For future use */
+	__u32 granule; /* how many PAGE_SIZE will do map/unmap once a time */
+	__u8 expansion[76];	/* For future use */
 };
 
 int main(int argc, char **argv)
@@ -51,11 +52,13 @@ int main(int argc, char **argv)
 	int threads = 1, seconds = 20, node = -1;
 	/* default dma mask 32bit, bidirectional DMA */
 	int bits = 32, xdelay = 0, dir = DMA_MAP_BIDIRECTIONAL;
+	/* default granule 1 PAGESIZE */
+	int granule = 1;
 
 	int cmd = DMA_MAP_BENCHMARK;
 	char *p;
 
-	while ((opt = getopt(argc, argv, "t:s:n:b:d:x:")) != -1) {
+	while ((opt = getopt(argc, argv, "t:s:n:b:d:x:g:")) != -1) {
 		switch (opt) {
 		case 't':
 			threads = atoi(optarg);
@@ -75,6 +78,9 @@ int main(int argc, char **argv)
 		case 'x':
 			xdelay = atoi(optarg);
 			break;
+		case 'g':
+			granule = atoi(optarg);
+			break;
 		default:
 			return -1;
 		}
@@ -110,6 +116,11 @@ int main(int argc, char **argv)
 		exit(1);
 	}
 
+	if (granule < 1 || granule > 1024) {
+		fprintf(stderr, "invalid granule size\n");
+		exit(1);
+	}
+
 	fd = open("/sys/kernel/debug/dma_map_benchmark", O_RDWR);
 	if (fd == -1) {
 		perror("open");
@@ -123,14 +134,15 @@ int main(int argc, char **argv)
 	map.dma_bits = bits;
 	map.dma_dir = dir;
 	map.dma_trans_ns = xdelay;
+	map.granule = granule;
 
 	if (ioctl(fd, cmd, &map)) {
 		perror("ioctl");
 		exit(1);
 	}
 
-	printf("dma mapping benchmark: threads:%d seconds:%d node:%d dir:%s\n",
-			threads, seconds, node, dir[directions]);
+	printf("dma mapping benchmark: threads:%d seconds:%d node:%d dir:%s granule: %d\n",
+			threads, seconds, node, dir[directions], granule);
 	printf("average map latency(us):%.1f standard deviation:%.1f\n",
 			map.avg_map_100ns/10.0, map.map_stddev/10.0);
 	printf("average unmap latency(us):%.1f standard deviation:%.1f\n",
