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    SubjectRe: [PATCH RFC v8 02/11] vhost: use batched get_vq_desc version
    On Mon, Jun 22, 2020 at 06:11:21PM +0200, Eugenio Perez Martin wrote:
    > On Mon, Jun 22, 2020 at 5:55 PM Michael S. Tsirkin <mst@redhat.com> wrote:
    > >
    > > 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?
    > >
    >
    > Hi Michael.
    >
    > No, sorry, as described in
    > http://doc.dpdk.org/guides/howto/virtio_user_as_exceptional_path.html.
    > But I could add to test it in the guest too.
    >
    > These kinds of raw packets "bursts" do not show performance
    > differences, but I could test deeper if you think it would be worth
    > it.

    Oh ok, so this is without guest, with virtio-user.
    It might be worth checking dpdk within guest too just
    as another data point.

    > > > * 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?
    >
    > Yes, sorry: Two virtio-net interfaces connected with a linux bridge in
    > the host. More precisely:
    > * Adding one of the interfaces to another namespace, assigning it an
    > IP, and starting netserver there.
    > * Assign another IP in the range manually to the other virtual net
    > interface, and start the desired test there.
    >
    > If you think it would be better to perform then differently please let me know.


    Not sure why you bother with namespaces since you said you are
    using L2 bridging. I guess it's unimportant.

    > >
    > > > - 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.
    > >
    >
    > Got it, will get back with the results.
    >
    > Thank you very much!
    >
    > >
    > >
    > > > - TCP_STREAM goes from ~10.7 gbps to ~7Gbps
    > > > - TCP_RR from 6223.64 transactions/sec to 5739.44
    > >

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