From e2dbfbdcf49380f3b972b65a64032c0e3b135373 Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <eelco.dolstra@logicblox.com>
Date: Sun, 13 Jun 2010 23:36:55 +0000
Subject: [PATCH] =?UTF-8?q?*=20Use=20writeback=20caching=20for=20virtual?=
 =?UTF-8?q?=20disks=20instead=20of=20writethrough=20=20=20caching.=20=20Th?=
 =?UTF-8?q?is=20makes=20a=20huge=20performance=20difference=20(e.g.=20from?=
 =?UTF-8?q?=204=20MB/s=20=20=20`dd'=20throughput=20to=20140=20MB/s=20on=20?=
 =?UTF-8?q?the=20Hydra=20machines).=20=20As=20the=20QEMU=20=20=20manual=20?=
 =?UTF-8?q?says:=20"Some=20block=20drivers=20perform=20badly=20with=20=20?=
 =?UTF-8?q?=20=E2=80=98cache=3Dwritethrough=E2=80=99,=20most=20notably,=20?=
 =?UTF-8?q?qcow2."?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

svn path=/nixos/branches/boot-order/; revision=22248
---
 modules/virtualisation/qemu-vm.nix | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/modules/virtualisation/qemu-vm.nix b/modules/virtualisation/qemu-vm.nix
index 6f8deebc69a..1cae5fef7c8 100644
--- a/modules/virtualisation/qemu-vm.nix
+++ b/modules/virtualisation/qemu-vm.nix
@@ -128,7 +128,7 @@ let
           -m ${toString config.virtualisation.memorySize} \
           -no-kvm-irqchip \
           -net nic,vlan=0,model=virtio -net user,vlan=0 -smb / \
-          -drive file=$NIX_DISK_IMAGE,if=virtio,boot=on,werror=report \
+          -drive file=$NIX_DISK_IMAGE,if=virtio,boot=on,cache=writeback,werror=report \
           -kernel ${config.system.build.toplevel}/kernel \
           -initrd ${config.system.build.toplevel}/initrd \
           ${qemuGraphics} \