Re: [PATCH 0/2] Send all the SVQ control commands in parallel

[Eugenio Perez Martin]

On Wed, Apr 19, 2023 at 1:50 PM Hawkins Jiawei <yin31149@gmail.com> wrote:
>
> This patchset allows QEMU to poll and check the device used buffer
> after sending all SVQ control commands, instead of polling and checking
> immediately after sending each SVQ control command, so that QEMU can
> send all the SVQ control commands in parallel, which have better
> performance improvement.
>
> I use vdpa_sim_net to simulate vdpa device, refactor
> vhost_vdpa_net_load() to call vhost_vdpa_net_load_mac() 30 times,
> refactor `net_vhost_vdpa_cvq_info.load` to call vhost_vdpa_net_load()
> 1000 times,

Maybe a little bit too high for real scenarios but it gives us a hint
for sure :). Maybe it is more realistic to send ~10 or ~100 commands?

>  to build a test environment for sending
> multiple SVQ control commands. Time in monotonic to
> finish `net_vhost_vdpa_cvq_info.load`:
>
>     QEMU                            monotonic time
> --------------------------------------------------
> not patched                              89202
> --------------------------------------------------
> patched                                  80455
>

Is time expressed in seconds or milliseconds? I'm going to assume ms.

So let's say all the time was spent in the context switch between qemu
and kernel, this is a save of (89202 - 80455)/30000 = 0.3 ms per
command?

Thanks!

> This patchset resolves the GitLab issue at
> https://gitlab.com/qemu-project/qemu/-/issues/1578.
>
> Hawkins Jiawei (2):
>   vdpa: rename vhost_vdpa_net_cvq_add()
>   vdpa: send CVQ state load commands in parallel
>
>  net/vhost-vdpa.c | 150 +++++++++++++++++++++++++++++++++++------------
>  1 file changed, 112 insertions(+), 38 deletions(-)
>
> --
> 2.25.1
>