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

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Date:   Mon, 22 Jun 2020 17:07:33 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Eugenio Perez Martin <eperezma@...hat.com>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Cc:     "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 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?


>    - 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.

Thanks