[Swan] XFRM pCPU Load distribution in KVM Muti-queue virtio-net

Rav Ya ravin.ya90 at gmail.com
Tue Sep 15 15:11:30 UTC 2020

Hello Everyone,

Please advice. Any help will be highly appreciated. Thank you in advance.

*Test Setup: *Libreswan Server (Virtual Machine: KVM)
500 IPSec Clients (xAuth using PAM-Auth)

I am running a Libreswan server in a virtual environment (VM hosted on
KVM/oVIRT). The logical network i.e. virtio-net virtual NIC drivers
supports Multiqueue. I have 6 vCPUs configured with 6 RX/TX Queue (1 queue
per vCPU).

The traffic load balancing over XFRM pCPU is flaky. Initially, the load
gets evenly distributed and after a while, only 1 (at most 2) vCPUs get
utilized with soft IRQs and the rest go underutilized.

I read an article that said XFRM pCPU only supports RSS NIC and
recently support for vmxnet3 (VMWare) got added. The KVM and virtio
Multiqueue was listed under future ideas and worklist.

Is there a way to work around this limitation? Is this support available on
the Latest version of Kernel and Libreswan? please advise.

Thank You,
-Rav Ya
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