Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Mon, 22 Jun 2020 11:55:04 -0400
From:   "Michael S. Tsirkin" <mst@redhat.com>
To:     Eugenio Perez Martin <eperezma@redhat.com>
Cc:     Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
        linux-kernel@vger.kernel.org, kvm list <kvm@vger.kernel.org>,
        virtualization@lists.linux-foundation.org, netdev@vger.kernel.org,
        Jason Wang <jasowang@redhat.com>
Subject: Re: [PATCH RFC v8 02/11] vhost: use batched get_vq_desc version
Message-ID: <20200622114622-mutt-send-email-mst@kernel.org>
References: <20200611113404.17810-1-mst@redhat.com>
 <20200611113404.17810-3-mst@redhat.com>
 <20200611152257.GA1798@char.us.oracle.com>
 <CAJaqyWdwXMX0JGhmz6soH2ZLNdaH6HEdpBM8ozZzX9WUu8jGoQ@mail.gmail.com>
 <CAJaqyWdwgy0fmReOgLfL4dAv-E+5k_7z3d9M+vHqt0aO2SmOFg@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <CAJaqyWdwgy0fmReOgLfL4dAv-E+5k_7z3d9M+vHqt0aO2SmOFg@mail.gmail.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

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
> <eperezma@redhat.com> wrote:
> >
> > On Thu, Jun 11, 2020 at 5:22 PM Konrad Rzeszutek Wilk
> > <konrad.wilk@oracle.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


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