Virtual machines can hang during the boot sequence if the number of grant references exceeds 32,768.
Messages such as the following are written to
/var/log/messages
:
timestamp
localhost kernel: xen_netfront: Initialising Xen virtual ethernet drivertimestamp
localhost kernel: xen_netfront: can't alloc rx grant refstimestamp
localhost kernel: net eth7: only created 7 queues
As of Oracle VM Release 3.4.1, the addition of multi-queue support for Xen network and block drivers to increase I/O throughput requires an increased number of grant references and queues.
Grant references relate to the Xen grant table mechanism. See the Xen documentation for more information.
Workaround: Decrease the value of
the xen_netback max_queues
option in the
/etc/modprobe.d/ovs.conf
file on Oracle VM Server.
The default value is 8
. You can decrease this
value to 2
, for example. After you save the
changes to ovs.conf
, you must restart
Oracle VM Server for them to take effect.
# Limit Xen netback max queue to 8 options xen_netback max_queues=2
Bug 22831141 and 22817043