KVM: use cache=unsafe

When running with raw image files, we're not passing in any cache= parameter, making KVM use the default. Unfortunately, the default is horribly slow and way too secure about data which doesn't matter for our build use case. So instead, we should just use cache=unsafe, rendering flush requests from the guest as nops, making builds faster by many times. Signed-off-by: Alexander Graf <[email protected]>
e9925248 · Oct 1, 2011 · 7aefa9e · 7aefa9e
1 parent d674a36
commit 7aefa9e
Showing 1 changed file with 3 additions and 1 deletion.
diff --git a/build b/build
@@ -1527,10 +1527,12 @@ for SPECFILE in "${SPECFILES[@]}" ; do
 	elif [ "$VM_TYPE" = 'qemu' -o "$VM_TYPE" = 'kvm' ]; then
 		echo "booting $VM_TYPE ..."
 		if [ "$kvm_virtio" = 1 ]; then
-		    CACHE=""
                     if [ "$VM_TYPE" = 'kvm' -a -b "$VM_IMAGE" ]; then
                       # speed optimization when using kvm with raw devices
 		      CACHE=",cache=none"
+                    else
+                      # speed optimization when using kvm with raw files
+		      CACHE=",cache=unsafe"
                     fi
 		    qemu_args=(-drive file="$VM_IMAGE",if=virtio$CACHE -hda "$VM_IMAGE")
 		    if [ -n "$VM_SWAP" ]; then