openstack/ironic
Code Issues Proposed changes

Remove use of nomodeset by default

Browse Source 
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
This commit is contained in:
Julia Kreger 2023-04-26 07:34:29 -07:00
parent 7083545731
commit f2605e9281
11 changed files with 48 additions and 18 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
devstack/lib/ironic
View File

@ -1793,7 +1793,7 @@ function configure_ironic_conductor {
-subj '/O=OpenStack/OU=DevStack Servers'
fi
local pxe_params="nofb nomodeset console=${IRONIC_TTY_DEV}"
local pxe_params="nofb console=${IRONIC_TTY_DEV}"
pxe_params+=" systemd.journald.forward_to_console=yes"
if is_service_enabled tls-proxy; then
pxe_params+=" ipa-insecure=1"
@ -1805,7 +1805,7 @@ function configure_ironic_conductor {
iniset $IRONIC_CONF_FILE pxe kernel_append_params "$pxe_params"
fi
local kernel_append_params="nofb nomodeset console=${IRONIC_TTY_DEV}"
local kernel_append_params="nofb console=${IRONIC_TTY_DEV}"
kernel_append_params+=" systemd.journald.forward_to_console=yes"
# NOTE(dtantsur): avoid setting ipa-insecure for redfish, we have a way to

2
devstack/tools/ironic/scripts/cirros-partition.sh
View File

@ -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

2
doc/source/admin/drivers/redfish.rst
View File

@ -214,7 +214,7 @@ user-specified kernel command line parameters.
.. code-block:: bash
baremetal node set node-0 \
--driver-info kernel_append_params="nofb nomodeset vga=normal"
--driver-info kernel_append_params="nofb vga=normal"
.. note::
The ``driver_info`` field is supported starting with the Xena release.

16
doc/source/admin/interfaces/boot.rst
View File

@ -49,7 +49,7 @@ configuration option:
.. code-block:: ini
[pxe]
kernel_append_params = nofb nomodeset vga=normal
kernel_append_params = nofb vga=normal
.. note::
The option was called ``pxe_append_params`` before the Xena cycle.
@ -59,9 +59,9 @@ Per-node and per-instance overrides are also possible, for example:
.. code-block:: bash
baremetal node set node-0 \
--driver-info kernel_append_params="nofb nomodeset vga=normal"
--driver-info kernel_append_params="nofb vga=normal"
baremetal node set node-0 \
--instance-info kernel_append_params="nofb nomodeset vga=normal"
--instance-info kernel_append_params="nofb vga=normal"
Starting with the Zed cycle, you can combine the parameters from the
configuration and from the node using the special ``%default%`` syntax:
@ -74,13 +74,21 @@ configuration and from the node using the special ``%default%`` syntax:
Together with the configuration above, the following parameters will be
appended to the kernel command line::
nofb nomodeset vga=normal console=ttyS0,115200n8
nofb vga=normal console=ttyS0,115200n8
.. note::
Ironic does not do any de-duplication of the resulting kernel parameters.
Both kernel itself and dracut seem to give priority to the last instance
of the same parameter.
.. warning::
Previously our documentation listed the Linux kernel parameter
``nomodeset`` as an option. This option is intended for troubleshooting,
and can greatly degrade performance with Matrox/Aspeed BMC Graphics
controllers which is very commonly used on physical servers. The
performance degredation can greatly reduce IO capacity upon every
console graphics update being written to the screen.
Common options
--------------

4
doc/source/install/include/kernel-boot-parameters.inc
View File

@ -91,7 +91,7 @@ respectively.
[pxe]
# Additional append parameters for baremetal PXE boot.
kernel_append_params = nofb nomodeset vga=normal console=ttyS0,115200n8
kernel_append_params = nofb vga=normal console=ttyS0,115200n8
* For node web console configuration is similar with the addition of ``ttyX``
@ -100,7 +100,7 @@ respectively.
[pxe]
# Additional append parameters for baremetal PXE boot.
kernel_append_params = nofb nomodeset vga=normal console=tty0 console=ttyS0,115200n8
kernel_append_params = nofb vga=normal console=tty0 console=ttyS0,115200n8
For detailed information on how to add consoles see the reference documents
`kernel params`_ and `serial console`_.

2
ironic/conf/ilo.py
View File

@ -112,7 +112,7 @@ opts = [
'This setting must be set to the octal number '
'representation, meaning starting with ``0o``.')),
cfg.StrOpt('kernel_append_params',
default='nofb nomodeset vga=normal',
default='nofb vga=normal',
mutable=True,
help=_('Additional kernel parameters to pass down to the '
'instance kernel. These parameters can be consumed by '

2
ironic/conf/pxe.py
View File

@ -24,7 +24,7 @@ from ironic.common.i18n import _
opts = [
cfg.StrOpt('kernel_append_params',
deprecated_name='pxe_append_params',
default='nofb nomodeset vga=normal',
default='nofb vga=normal',
mutable=True,
help=_('Additional append parameters for baremetal PXE boot.')),
cfg.StrOpt('default_ephemeral_format',

2
ironic/conf/redfish.py
View File

@ -64,7 +64,7 @@ opts = [
'auto-expire. Applies only when `use_swift` is '
'enabled.')),
cfg.StrOpt('kernel_append_params',
default='nofb nomodeset vga=normal',
default='nofb vga=normal',
mutable=True,
help=_('Additional kernel parameters to pass down to the '
'instance kernel. These parameters can be consumed by '

8
ironic/tests/unit/drivers/modules/test_image_utils.py
View File

@ -583,7 +583,7 @@ class RedfishImageUtilsTestCase(db_base.DbTestCase):
mock_create_boot_iso.assert_called_once_with(
mock.ANY, mock.ANY, 'http://kernel/img', 'http://ramdisk/img',
boot_mode='uefi', esp_image_href='http://bootloader/img',
kernel_params='nofb nomodeset vga=normal',
kernel_params='nofb vga=normal',
root_uuid='1be26c0b-03f2-4d2e-ae87-c02d7f33c123',
inject_files=None)
@ -604,7 +604,7 @@ class RedfishImageUtilsTestCase(db_base.DbTestCase):
mock_create_boot_iso.assert_called_once_with(
mock.ANY, mock.ANY, 'http://kernel/img', 'http://ramdisk/img',
boot_mode='uefi', esp_image_href=None,
kernel_params='nofb nomodeset vga=normal',
kernel_params='nofb vga=normal',
root_uuid='1be26c0b-03f2-4d2e-ae87-c02d7f33c123',
inject_files=None)
@ -633,7 +633,7 @@ class RedfishImageUtilsTestCase(db_base.DbTestCase):
mock_create_boot_iso.assert_called_once_with(
mock.ANY, mock.ANY, 'http://kernel/img', 'http://ramdisk/img',
boot_mode='bios', esp_image_href=None,
kernel_params='nofb nomodeset vga=normal',
kernel_params='nofb vga=normal',
root_uuid='1be26c0b-03f2-4d2e-ae87-c02d7f33c123',
inject_files=None)
@ -702,7 +702,7 @@ class RedfishImageUtilsTestCase(db_base.DbTestCase):
mock_create_boot_iso.assert_called_once_with(
mock.ANY, mock.ANY, 'http://kernel/img', 'http://ramdisk/img',
boot_mode='uefi', esp_image_href=None,
kernel_params=f'nofb nomodeset vga=normal {kernel_params}',
kernel_params=f'nofb vga=normal {kernel_params}',
root_uuid='1be26c0b-03f2-4d2e-ae87-c02d7f33c123',
inject_files=None)

2
ironic/tests/unit/drivers/modules/test_ipxe.py
View File

@ -813,7 +813,7 @@ class iPXEBootTestCase(db_base.DbTestCase):
'aki_path': 'http://192.1.2.3:1234/' + uuid + '/kernel',
'ari_path': 'http://192.1.2.3:1234/' + uuid + '/ramdisk',
'ramdisk_opts': 'cat meow',
'pxe_append_params': 'nofb nomodeset vga=normal ipa-debug=1 '
'pxe_append_params': 'nofb vga=normal ipa-debug=1 '
'ipa-global-request-'
'id=' + task.context.request_id,
'tftp_server': mock.ANY,

22
releasenotes/notes/remove-nomodset-7a352a9519c1045b.yaml Normal file
View File

@ -0,0 +1,22 @@
---
upgrade:
- |
The defaults for ``kernel_append_params`` have had the Linux kernel
command line parameter ``nomodeset`` removed from the defaults for the
``kernel_append_params`` settings. The ``nomodeset`` option is for
troubleshooting and changes the behavior of the graphics interface
such that memory can be locked upon graphical updates on physical
servers with BMC graphical interfaces, which results in spikes in
latency and packet loss whenever graphics updates occur. Operators
may add the option to their local configuration, but should be aware
that large image transfers or other high IO operations can be impacted.
fixes:
- |
Agents deploying on physical servers with default kernel arguments were
suspetible to packet loss if a Matrox VGA/Aspeed BMC Graphics interface
is present on the machine. The defaults have been changed to remove
the use of the ``nomodeset`` kernel command line parameter which
should only be used for troubleshooting as it has been determined
that the memory updates can lock all of the kernel memory upon any
console graphics update which can negatively impact IO for Networking
or Disk interactions.