Bug 1983828

Summary:	[DDF] we do not support the use of TAP interfaces with ovs-dpdk and never have.
Product:	Red Hat OpenStack	Reporter:	Direct Docs Feedback <ddf-bot>
Component:	documentation	Assignee:	mgeary <mgeary>
Status:	CLOSED CURRENTRELEASE	QA Contact:	RHOS Documentation Team <rhos-docs>
Severity:	unspecified	Docs Contact:
Priority:	unspecified
Version:	13.0 (Queens)	CC:	cfields, igallagh, mgeary, rheslop, smooney
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Hardware:	All
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Last Closed:	2022-01-27 13:44:30 UTC	Type:	---
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oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
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Description Direct Docs Feedback 2021-07-19 22:29:58 UTC

we do not support the use of TAP interfaces with ovs-dpdk and never have.

The step descried in this doc including using udev rules to modify tap device are not supported in OSP
the document also states

" This is documented in the libvirt domain spec for KVM and can be done with virsh edit on a RHEL KVM hypervisor. "

we do not suppoprt the use of virsh edit ever in openstack and if customer us it it will render there vm unsupported.

the correct way to cange the tx/rx queue lenght is to set the tx_queue_size and rx_queue_size
paramaters

https://docs.openstack.org/nova/latest/configuration/config.html#libvirt.rx_queue_size

https://docs.openstack.org/nova/latest/configuration/config.html#libvirt.tx_queue_size

Reported by: smooney

https://access.redhat.com/documentation/en-us/red_hat_openstack_platform/13/html/ovs-dpdk_end_to_end_troubleshooting_guide/high_packet_loss_in_the_tx_queue_of_the_instance_s_tap_interface#annotations:5767a912-9b85-4719-9d00-c34a848290c2

Comment 1 smooney 2021-07-20 12:07:44 UTC

it looks like that incorrect info may have orginally came form https://access.redhat.com/solutions/2785881

it would have worked for none ovs-dpdk environment before we added the capablity to manage queue lenght via nova
but this type of turning of tap devices outside of openstack is not something we should be supporting in OSP today.

let ensure that https://access.redhat.com/solutions/2785881 is also removed.

Comment 2 Chris Fields 2021-09-07 21:46:10 UTC

The KCS https://access.redhat.com/solutions/2785881 has been updated to remove the unsupported work around for modifying qlen for via udev.  That section has been replaced with a link to "Change RX queue size and TX queue size of virtio NICs deployed with Red Hat OpenStack Director" at https://access.redhat.com/solutions/3641441.

Comment 5 mgeary 2022-01-19 16:51:36 UTC

updates published at 
https://access.redhat.com/documentation/en-us/red_hat_openstack_platform/13/html-single/ovs-dpdk_end_to_end_troubleshooting_guide/index#high_packet_loss_in_the_tx_queue_of_the_instance_s_tap_interface