Re: [dpdk-dev] [RFC 00/14] vhost: clean-up and simplify async implementation

["Hu, Jiayu" <jiayu.hu@intel.com>]

Hi Maxime,

> -----Original Message-----
> From: Maxime Coquelin <maxime.coquelin@redhat.com>
> Sent: Friday, October 8, 2021 6:00 AM
> To: dev@dpdk.org; Xia, Chenbo <chenbo.xia@intel.com>; Hu, Jiayu
> <jiayu.hu@intel.com>; Wang, YuanX <yuanx.wang@intel.com>; Ma,
> WenwuX <wenwux.ma@intel.com>; Richardson, Bruce
> <bruce.richardson@intel.com>; Mcnamara, John
> <john.mcnamara@intel.com>
> Cc: Maxime Coquelin <maxime.coquelin@redhat.com>
> Subject: [RFC 00/14] vhost: clean-up and simplify async implementation
> 
> This series aims at cleaning and simplifying the async enqueue path. I think it
> makes the code easier to understand, and is necessary before integrating
> new changes.

I really appreciate those changes, and the code looks better, especially for
improving io vector logic, as the existed implementation has a potential risk
of OOB reads/writes.

About the fifth patch, removing async batch threshold, this change is OK for me,
as current vhost is packet level offloading and buffer level DMA batching copy
will be done inside the DMA callback, so no need to keep the batching threshold.
But when integrate DMA logic inside vhost, the async data path still needs to handle
buffer level batching, and some of deleted code may need to be recovered.

Thanks,
Jiayu
> 
> I may have more reworks to propose in next revisions, but I wanted to share
> my current status early so that you have time to review/test it.
> 
> It is only compile-tested, as I don't have HW with IOAT support to test it.
> 
> Maxime Coquelin (14):
>   vhost: move async data in a dedicated structure
>   vhost: hide inflight async structure
>   vhost: simplify async IO vectors
>   vhost: simplify async IO vectors iterators
>   vhost: remove async batch threshold
>   vhost: introduce specific iovec structure
>   vhost: remove useless fields in async iterator struct
>   vhost: improve IO vector logic
>   vhost: remove notion of async descriptor
>   vhost: simplify async enqueue completion
>   vhost: simplify getting the first in-flight index
>   vhost: prepare async for mbuf to desc refactoring
>   vhost: prepare sync for mbuf to desc refactoring
>   vhost: merge sync and async mbuf to desc filling
> 
>  examples/vhost/ioat.c       |  30 +-
>  examples/vhost/ioat.h       |   2 +-
>  lib/vhost/rte_vhost_async.h |  42 +--
>  lib/vhost/vhost.c           | 129 +++----
>  lib/vhost/vhost.h           |  67 ++--
>  lib/vhost/vhost_user.c      |   4 +-
>  lib/vhost/virtio_net.c      | 697 ++++++++++++++----------------------
>  7 files changed, 379 insertions(+), 592 deletions(-)
> 
> --
> 2.31.1