Remove use of nomodeset by default

The troubleshooting kernel command line option nomodeset
unfortunately changes the way framebuffer interactions work
with graphics devices which in some cases can result in kernel
memory to be used for graphics updates. When this happens on
some specific hardware common in rack mount servers with baseboard
management controllers, this can cause the memory bus to become
locked for a brief time while the graphics update is occuring.

This locked memory bus means disk IO can become blocked,
and network cards can overflow their buffers resulting in
packet loss on top of the latency incurred by the graphics
update executing.

As such, we've removed the nomodeset option from default usage and
added a note describing its removal to the documentation along
with a release note.

Change-Id: I9084d88c3ec6f13bd64b8707892758fa87dd7f86

1 files changed, 1 insertions, 1 deletions

diff --git a/devstack/tools/ironic/scripts/cirros-partition.sh b/devstack/tools/ironic/scripts/cirros-partition.sh
index facf9b030..38e1764c4 100755
--- a/devstack/tools/ironic/scripts/cirros-partition.sh
+++ b/devstack/tools/ironic/scripts/cirros-partition.sh
@@ -18,7 +18,7 @@ IRONIC_TTY_DEV=${IRONIC_TTY_DEV:-ttyS0,115200}
 # rdroot : boot from the ramdisk present on the root partition instead of
 #          mounting the root partition.
 # dslist : disable Nova metadata support, it takes a long time on boot.
-KARGS=${KARGS:-nofb nomodeset vga=normal console=${IRONIC_TTY_DEV} rdroot dslist=configdrive}
+KARGS=${KARGS:-nofb vga=normal console=${IRONIC_TTY_DEV} rdroot dslist=configdrive}
 
 workdir=$(mktemp -d)
 root_mp=$workdir/root