On Fri, Jun 19, 2020 at 08:07:57PM +0200, Eugenio Perez Martin wrote:

On Mon, Jun 15, 2020 at 2:28 PM Eugenio Perez Martin
[off-list ref] wrote:

quoted

On Thu, Jun 11, 2020 at 5:22 PM Konrad Rzeszutek Wilk
[off-list ref] wrote:

quoted

On Thu, Jun 11, 2020 at 07:34:19AM -0400, Michael S. Tsirkin wrote:

quoted

As testing shows no performance change, switch to that now.

What kind of testing? 100GiB? Low latency?

Hi Konrad.

I tested this version of the patch:
https://lkml.org/lkml/2019/10/13/42

It was tested for throughput with DPDK's testpmd (as described in
http://doc.dpdk.org/guides/howto/virtio_user_as_exceptional_path.html)
and kernel pktgen. No latency tests were performed by me. Maybe it is
interesting to perform a latency test or just a different set of tests
over a recent version.

Thanks!

I have repeated the tests with v9, and results are a little bit different:
* If I test opening it with testpmd, I see no change between versions

OK that is testpmd on guest, right? And vhost-net on the host?

* If I forward packets between two vhost-net interfaces in the guest
using a linux bridge in the host:

And here I guess you mean virtio-net in the guest kernel?

  - netperf UDP_STREAM shows a performance increase of 1.8, almost
doubling performance. This gets lower as frame size increase.
  - rests of the test goes noticeably worse: UDP_RR goes from ~6347
transactions/sec to 5830

OK so it seems plausible that we still have a bug where an interrupt
is delayed. That is the main difference between pmd and virtio.
Let's try disabling event index, and see what happens - that's
the trickiest part of interrupts.

  - TCP_STREAM goes from ~10.7 gbps to ~7Gbps
  - TCP_RR from 6223.64 transactions/sec to 5739.44