[PATCH] vhost: support sync copy when data buffer is small

[Hu, Jiayu]

Hi Maxime,

> -----Original Message-----
> From: Maxime Coquelin <maxime.coquelin at redhat.com>
> Sent: Tuesday, April 19, 2022 5:10 PM
> To: Ma, WenwuX <wenwux.ma at intel.com>; Xia, Chenbo
> <chenbo.xia at intel.com>; dev at dpdk.org
> Cc: Hu, Jiayu <jiayu.hu at intel.com>; Wang, Yinan <yinan.wang at intel.com>;
> He, Xingguang <xingguang.he at intel.com>; Ling, WeiX <weix.ling at intel.com>
> Subject: Re: [PATCH] vhost: support sync copy when data buffer is small
> 
> Hi Wenwu,
> 
> On 4/11/22 15:38, Wenwu Ma wrote:
> > In async datapath, if the length of data buffer is less than 256, the
> > data will be copied by CPU instead of DMA.
> >
> > Signed-off-by: Wenwu Ma <wenwux.ma at intel.com>
> > ---
> >   lib/vhost/vhost.h      |  6 ++-
> >   lib/vhost/virtio_net.c | 96 ++++++++++++++++++++++++++++++------------
> >   2 files changed, 73 insertions(+), 29 deletions(-)
> >
> 
> As I mentioned in the past, let's have a DMA-only solution working before
> trying to support CPU copy for small packets.

Thanks for your suggestion.

For "DMA-only solution working", do you mean community reaches an
agreement on OVS DSA design? The reason of asking this question is
that we will have some following patches around async vhost in 22.11,
like vhostpmd supporting async vhost data-path. Regarding your suggestion,
do you think they also need to be deferred until "DMA-only solution working"?

Thanks,
Jiayu

> 
> Thanks,
> Maxime