[virtio-comment] Re: [PATCH v2 05/11] transport-fabrics: introduce Keyed Transmission

[Stefan Hajnoczi <stefanha@redhat.com>]

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On Thu, May 04, 2023 at 04:19:04PM +0800, zhenwei pi wrote:
> Keyed transmission is used for message oriented communication(Ex RDMA),
> also add virtio-blk read/write 8K example.
> 
> Signed-off-by: zhenwei pi <pizhenwei@bytedance.com>
> ---
>  transport-fabrics.tex | 178 ++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 178 insertions(+)
> 
> diff --git a/transport-fabrics.tex b/transport-fabrics.tex
> index c02cf26..7711321 100644
> --- a/transport-fabrics.tex
> +++ b/transport-fabrics.tex
> @@ -317,3 +317,181 @@ \subsubsection{Buffer Mapping Definition}\label{sec:Virtio Transport Options / V
>                      |......|
>                      +------+  -> 8193
>  \end{lstlisting}
> +
> +\paragraph{Keyed Transmission}\label{sec:Virtio Transport Options / Virtio Over Fabrics / Transmission Protocol / Commands Definition / Keyed Transmission}
> +Command and Segment Descriptors are transmitted in a message within a
> +connection, and buffer is transmitted by remote memory access.  The layout in message:

With RDMA it is theoretically possible to implement virtqueues without
messages in the data path (i.e. by using something similar to vring with
RDMA). Why did you decide to use a mixed messages + RDMA approach
instead of a 100% RDMA approach?

> +
> +\begin{lstlisting}
> +CMDx contains 0 descriptor, CMDy contains (n - m + 1) descriptors:

"0 descriptors"

> +
> +     +-----+     +-----++-----+     +-----+
> + ... | CMDx| ... | CMDy||DESCm| ... |DESCn| ...
> +     +-----+     +-----++-----+     +-----+
> +
> +COMPx contains 0 descriptor, COMPy contains 0 descriptor:

"0 descriptors"

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