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Subject: Re: [PATCH RFC 0/2] Packed ring for vhost
To:     mst@redhat.com, virtualization@lists.linux-foundation.org,
        linux-kernel@vger.kernel.org, netdev@vger.kernel.org
Cc:     wexu@redhat.com, jfreimann@redhat.com, tiwei.bie@intel.com
References: <1518575829-1431-1-git-send-email-jasowang@redhat.com>
From:   Jason Wang <jasowang@redhat.com>
Message-ID: <1c200171-5d72-f410-7637-1ade5f41b550@redhat.com>
Date:   Wed, 14 Feb 2018 10:43:29 +0800
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On 2018年02月14日 10:37, Jason Wang wrote:
> Hi all:
>
> This RFC implement a subset of packed ring which was described at
> https://github.com/oasis-tcs/virtio-docs/blob/master/virtio-v1.1-packed-wd07.pdf
> . The code were tested with pmd implement by Jens at
> http://dpdk.org/ml/archives/dev/2018-January/089417.html. Minor
> change was needed for pmd codes to kick virtqueue since it assumes a
> busy polling backend.
>
> Test were done between localhost and guest. Testpmd (rxonly) in guest
> reports 2.4Mpps. Testpmd (txonly) repots about 2.1Mpps.
>
> It's not a complete implemention, here's what were missed:
>
> - Device Area
> - Driver Area
> - Descriptor indirection
> - Zerocopy may not be functional
> - Migration path is not tested
> - Vhost devices except for net
> - vIOMMU can not work (mainly because the metadata prefetch is not
>    implemented).
> - See FIXME/TODO in the codes for more details
> - No batching or other optimizations were implemented
>
> For a quick prototype, this series open code the tracking of warp
> counter and descriptor index at net device. This will be addressed in
> the future by:
>
> - Move get_rx_bufs() from net.c to vhost.c
> - Let vhost_get_vq_desc() returns vring_used_elem instad of head id
>
> With the above, we can hide the internal (at least part of) vring
> layout from specific device.
>
> Please review.
>
> Thanks

It's near spring festival in China, will probably reply after the holiday.

Thanks