dd: default to 64k block size

So that it's no longer CPU bound when running 1 dd on RAID arrays.
fengguang · Apr 21, 2012 · f77bab4 · f77bab4
1 parent f538bf6
commit f77bab4
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Showing 2 changed files with 6 additions and 2 deletions.
diff --git a/config.sh b/config.sh
@@ -21,7 +21,7 @@ NFS_DEVICE=192.168.1.91:/nfs
 #
 # block size for dd
 #
-bs=4k
+bs=64k
 
 #
 # repeat each test so many times

diff --git a/dd-common.sh b/dd-common.sh
@@ -20,14 +20,18 @@ run_fio() {
 }
 
 run_dd() {
+	local bs_opt
+	# dd defaults to bs=512 which could make it CPU bound
+	[[ dd_opt =~ 'bs=' ]] || bs_opt="bs=${bs:-64k}"
+
 	for i in `seq $nr_dd`
 	do
 		for dev in $bdevs
 		do
 			mnt=$MNT/$(basename $dev)
 			rm -f $mnt/zero-$i
 			# ulimit -m $((i<<10))
-			dd $(echo $dd_opt | tr : ' ') if=/dev/zero of=$mnt/zero-$i &
+			dd $bs_opt $(echo $dd_opt | tr : ' ') if=/dev/zero of=$mnt/zero-$i &
 			echo $! >> pid
 			# sleep 5
 		done
-Original file line number
+Diff line change
@@ Expand Up / @@ -21,7 +21,7 @@ NFS_DEVICE=192.168.1.91:/nfs @@
     #
     # block size for dd
     #
-    bs=4k
+    bs=64k
     #
     # repeat each test so many times
@@ Expand Down @@