On Mon, Jan 10, 2022 at 3:24 PM Xuan Zhuo <xuanz...@linux.alibaba.com> wrote:
>
> On Mon, 10 Jan 2022 14:43:39 +0800, Jason Wang <jasow...@redhat.com> wrote:
> >
> > 在 2022/1/7 下午2:33, Xuan Zhuo 写道:
> > > In the scenario where indirect is not used, each desc corresponds to an
> > > extra, which is used to record information such as dma, flags, and
> > > next.
> > >
> > > In the scenario of using indirect, the assigned desc does not have the
> > > corresponding extra record dma information, and the dma information must
> > > be obtained from the desc when unmap.
> > >
> > > This patch allocates the corresponding extra array when indirect desc is
> > > allocated. This has these advantages:
> > > 1. Record the dma information of desc, no need to read desc when unmap
> > > 2. It will be more convenient and unified in processing
> > > 3. Some additional information can be recorded in extra, which will be
> > >     used in subsequent patches.
> >
> >
> > Two questions:
> >
> > 1) Is there any performance number for this change? I guess it gives
> > more stress on the cache.
>
> I will add performance test data in the next version.
>
> > 2) Is there a requirement to mix the pre mapped sg with unmapped sg? If
> > not, a per virtqueue flag looks sufficient
>
> There is this requirement. For example, in the case of AF_XDP, a patcket
> contains two parts, one is virtio_net_hdr, and the other is the actual data
> packet from AF_XDP. The former is unmapped sg, and the latter is pre mapped 
> sg.

Any chance to map virtio_net_hdr() manually by AF_XDP routine in this case?

Thanks

>
> Thanks.
>
> >
> > Thanks
> >
> >
>

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