** Changed in: nova/train Status: Fix Committed => Fix Released -- You received this bug notification because you are a member of Yahoo! Engineering Team, which is subscribed to OpenStack Compute (nova). https://bugs.launchpad.net/bugs/1847367
Title: Images with hw:vif_multiqueue_enabled can be limited to 8 queues even if more are supported Status in OpenStack Compute (nova): Fix Released Status in OpenStack Compute (nova) queens series: Triaged Status in OpenStack Compute (nova) rocky series: Triaged Status in OpenStack Compute (nova) stein series: Triaged Status in OpenStack Compute (nova) train series: Fix Released Bug description: Nova version: 18.2.3 Release: Rocky Compute node OS: CentOS 7.3 Compute node kernel: 3.10.0-327.13.1.el7.x86_64 In https://bugs.launchpad.net/nova/+bug/1570631 and commit https://review.opendev.org/#/c/332660/, a bug was fixed by making the assumption that the kernel version should also dictate the max number of queues on the tap interface when setting hw:vif_multiqueue_enabled=True. It was decided that 3.x kernels have a max queue count of 8. Unfortunately not all distributions follow this, and CentOS/RHEL has supported up to 256 queues since at least 7.2 even with a 3.x kernel. The result of this is that a 20 core VM created in Mitaka will have 20 queues enabled (because the limit of 8 had not been added). The very same host after being upgraded to Rocky will instead only give 8 queues to the VM even though the kernel supports 256. Could a workaround option be implemented to disable this check, or manually define the max queue count? Snippet of drivers/net/tun.c from CentOS 7.2 kernel source code: /* MAX_TAP_QUEUES 256 is chosen to allow rx/tx queues to be equal * to max number of VCPUs in guest. */ #define MAX_TAP_QUEUES 256 #define MAX_TAP_FLOWS 4096 Snippet from the 3.10.0 kernel code from https://elixir.bootlin.com/linux/v3.10/source/drivers/net/tun.c: /* DEFAULT_MAX_NUM_RSS_QUEUES were choosed to let the rx/tx queues allocated for * the netdevice to be fit in one page. So we can make sure the success of * memory allocation. TODO: increase the limit. */ #define MAX_TAP_QUEUES DEFAULT_MAX_NUM_RSS_QUEUES #define MAX_TAP_FLOWS 4096 In the above example, DEFAULT_MAX_NUM_RSS_QUEUES is set to 8. To manage notifications about this bug go to: https://bugs.launchpad.net/nova/+bug/1847367/+subscriptions -- Mailing list: https://launchpad.net/~yahoo-eng-team Post to : yahoo-eng-team@lists.launchpad.net Unsubscribe : https://launchpad.net/~yahoo-eng-team More help : https://help.launchpad.net/ListHelp