Re: [PATCH 1/2] vhost: allow multiple workers threads

On Tue, 2012-02-21 at 05:21 +0200, Michael S. Tsirkin wrote:

On Mon, Feb 20, 2012 at 05:04:10PM -0800, Shirley Ma wrote:

quoted

On Mon, 2012-02-20 at 23:00 +0200, Michael S. Tsirkin wrote:

quoted

The point was really to avoid scheduler overhead
as with tcp, tx and rx tend to run on the same cpu.

We have tried different approaches in the past, like splitting vhost
thread to separate TX, RX threads; create per cpu vhost thread

instead

quoted

of creating per VM per virtio_net vhost thread... 

We think per cpu vhost thread is a better approach based on the data

we

quoted

have collected. It will reduce both vhost resource and scheduler
overhead. It will not depend on host scheduler, has less various.

The

quoted

patch is under testing, we hope we can post it soon.

Thanks
Shirley

Yes, great, this is definitely interesting. I actually started with
a per-cpu one - it did not perform well but I did not
figure out why, switching to a single thread fixed it
and I did not dig into it.

The patch includes per cpu vhost thread & vhost NUMA aware scheduling

It is very interesting. We are collecting performance data with
different workloads (streams, request/response) related to which VCPU
runs on which CPU, which vhost cpu thread is being scheduled, and which
NIC TX/RX queues is being used. The performance were different when
using different vhost scheduling approach for both TX/RX worker. The
results seems pretty good: like 60 UDP_RRs, the results event more than
doubled in our lab. However the TCP_RRs results couldn't catch up
UDP_RRs.

Thanks
Shirley