From afa611c4e5c7b73159f5488a83b095e8e86386d2 Mon Sep 17 00:00:00 2001
From: Julia Kreger <juliaashleykreger@gmail.com>
Date: Fri, 16 Aug 2019 08:02:52 -0400
Subject: [PATCH] Move to unsafe caching

Currently we use writeback caching for disks
on our test vms, however that honors syncs and
IO could become blocked/locked if the sync has
not completed with the double virtualization that
occurs in CI.

In theory, we don't need to worry about the
buffer cache behavior for our test VMs.

Overall, it appears that there is a performance
gain of about 10-15% with making this change because
we're not honoring syncs to not lock-up IO.

Change-Id: Ib09dd7fd41c6b1cbc0e2b707bfc9e4ff8dfa6fad
---
 devstack/tools/ironic/templates/vm.xml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/devstack/tools/ironic/templates/vm.xml b/devstack/tools/ironic/templates/vm.xml
index 2be30a549a..ef2b3876ed 100644
--- a/devstack/tools/ironic/templates/vm.xml
+++ b/devstack/tools/ironic/templates/vm.xml
@@ -32,7 +32,7 @@
     <emulator>{{ emulator }}</emulator>
     {% for (imagefile, letter) in images %}
     <disk type='file' device='disk'>
-      <driver name='qemu' type='{{ disk_format }}' cache='writeback'/>
+      <driver name='qemu' type='{{ disk_format }}' cache='unsafe'/>
       <source file='{{ imagefile }}'/>
       <!-- NOTE(lucasagomes): The virtio disk controller apparently does
            not work with UEFI, so let's use IDE. -->