Bug ID 634132: VE: virtio high performance driver (Linux/KVM)

Last Modified: Oct 06, 2020

Bug Tracker

Affected Product:  See more info
BIG-IP VE(all modules)

Known Affected Versions:

Fixed In:
13.0.0 HF1

Opened: Dec 16, 2016
Severity: 2-Critical


By default, the UNIC driver is used for virtio devices on Linux/KVM hypervisors, and at higher network speeds, the soft IRQ interrupt load competes with tmm. This can be observed under load with the "top" linux command showing ksoftirqd soft IRQ load.


Potential performance issues (CPU utilization, throughput, connections/second).


Version 13.0.0 default behavior on Linux/KVM hypervisor with virtio nic(s) presented to the guest. Note: To determine what driver is in use for each nic, use following command: tmctl -d blade tmm/device_probed.



Fix Information

For higher performance with virtio nics (relevant on Linux/KVM hypervisors), a new sys db variable supports switching to a TMM native driver.

Behavior Change