linux-kernel - Re: [PATCH RFC v8 02/11] vhost: use batched get_vq

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Message-ID: <CAJaqyWdo1J-EoGUj3e2jM6USo0SEOM3xydoaYMhta0Y_YPyS_g@mail.gmail.com>
Date:   Mon, 22 Jun 2020 12:44:17 +0200
From:   Eugenio Perez Martin <eperezma@...hat.com>
To:     Jason Wang <jasowang@...hat.com>
Cc:     Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        linux-kernel@...r.kernel.org, kvm list <kvm@...r.kernel.org>,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org
Subject: Re: [PATCH RFC v8 02/11] vhost: use batched get_vq_desc version

On Mon, Jun 22, 2020 at 11:07 AM Jason Wang <jasowang@...hat.com> wrote:
>
>
> On 2020/6/20 上午2:07, Eugenio Perez Martin wrote:
> > On Mon, Jun 15, 2020 at 2:28 PM Eugenio Perez Martin
> > <eperezma@...hat.com> wrote:
> >> On Thu, Jun 11, 2020 at 5:22 PM Konrad Rzeszutek Wilk
> >> <konrad.wilk@...cle.com> wrote:
> >>> On Thu, Jun 11, 2020 at 07:34:19AM -0400, Michael S. Tsirkin wrote:
> >>>> 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
> > * If I forward packets between two vhost-net interfaces in the guest
> > using a linux bridge in the host:
> >    - 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
> >    - TCP_STREAM goes from ~10.7 gbps to ~7Gbps
>
>
> Which direction did you mean here? Guest TX or RX?

Hi Jason.

For both I created a linux bridge in the host, attach two guest
interfaces with vhost-net, and make the netperf run on them.

>
>
> >    - TCP_RR from 6223.64 transactions/sec to 5739.44
>
>
> Perf diff might help. I think we can start from the RR result which
> should be easier. Maybe you can test it for each patch then you may see
> which patch is the source of the regression.
>

Ok, I will look for differences.

Thanks!

> Thanks
>