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Subject: [PATCH v2 11/11] transport-fabrics: support inline data for keyed transmission
Add transport feature 'virtio_of_feature_stream_size' to negotiate
the inline data size. Lots of Virtio device protocol has small size
field(typically, 'status' to indicate the result of request), to
reduce the network RTT, support inline data for keyed transmission.
Signed-off-by: zhenwei pi <pizhenwei@bytedance.com>
---
transport-fabrics.tex | 113 ++++++++++++++++++++++++++++++++++++++++++
1 file changed, 113 insertions(+)
diff --git a/transport-fabrics.tex b/transport-fabrics.tex
index af35622..1e76bc6 100644
--- a/transport-fabrics.tex
+++ b/transport-fabrics.tex
@@ -496,6 +496,117 @@ \subsubsection{Buffer Mapping Definition}\label{sec:Virtio Transport Options / V
+------+
\end{lstlisting}
+For effective transmission, stream Segment Descriptors and keyed Segment
+Descriptors are allowed to use together in a single command.
+
+\begin{itemize}
+\item The initiator MAY discover the maximum stream transmission size of a
+command supported by target. See \ref{sec:Virtio Transport Options / Virtio Over Fabrics / Transmission Protocol / Opcodes Definition / virtio_of_op_get_feature}~\nameref{sec:Virtio Transport Options / Virtio Over Fabrics / Transmission Protocol / Opcodes Definition / virtio_of_op_get_feature}.
+\item The initiator MAY set the maximum stream transmission size of a command
+supported by initiator. See \ref{sec:Virtio Transport Options / Virtio Over Fabrics / Transmission Protocol / Opcodes Definition / virtio_of_op_set_feature}~\nameref{sec:Virtio Transport Options / Virtio Over Fabrics / Transmission Protocol / Opcodes Definition / virtio_of_op_set_feature}.
+\end{itemize}
+
+An example of 16 bytes maximum stream transmission size supported by target,
+and 1 byte maximum stream transmission size supported by initiator, a virtio-blk
+read 8K request(total size: sizeof(Command) + 4 * sizeof(Descriptor) + 16):
+\begin{lstlisting}
+ COMMAND +------+
+ |opcode| -> virtio_of_op_vring
+ +------+
+ |cmd id| -> 100
+ +------+
+ |length| -> 16 (virtio blk read command)
+ +------+
+ |ndesc | -> 4
+ +------+
+ |rsvd |
+ +------+
+
+ DESC0 +------+
+ +-|addr | -> 0
+ | +------+
+ | |length| -> 16
+ | +------+
+ | |id | -> 0
+ | +------+
+ | |flags | -> 0
+ | +------+
+ |
+ DESC1 | +------+
+ | |addr | -> 0xffff012345670000
+ | +------+
+ | |length| -> 4096
+ | +------+
+ | |id | -> 1
+ | +------+
+ | |flags | -> VIRTIO_OF_DESC_F_KEYED | VIRTIO_OF_DESC_F_WRITE
+ | +------+
+ | |key | -> 0x1238
+ | +------+
+ |
+ DESC2 | +------+
+ | |addr | -> 0xffff012345671000
+ | +------+
+ | |length| -> 4096
+ | +------+
+ | |id | -> 2
+ | +------+
+ | |flags | -> VIRTIO_OF_DESC_F_KEYED | VIRTIO_OF_DESC_F_WRITE
+ | +------+
+ | |key | -> 0x1239
+ | +------+
+ |
+ DESC3 | +------+
+ | |addr | -> 0xffff012345673000
+ | +------+
+ | |length| -> 1
+ | +------+
+ | |id | -> 3
+ | +------+
+ | |flags | -> VIRTIO_OF_DESC_F_KEYED | VIRTIO_OF_DESC_F_WRITE
+ | +------+
+ | |key | -> 0x1233
+ | +------+
+ |
+ DATA +>+------+ -> 0
+ |......|
+ +------+ -> 16
+\end{lstlisting}
+
+The target MAY handle Command, reads 16 bytes from request described by DESC0,
+writes the remote addresses of DESC1/DESC2, then responses Completion(total
+size: sizeof(Completion) + sizeof(Descriptor) + 1):
+\begin{lstlisting}
+ COMPLETION +------+
+ |status| -> VIRTIO_OF_SUCCESS
+ +------+
+ |cmd id| -> 10
+ +------+
+ |ndesc | -> 1
+ +------+
+ |rsvd |
+ +------+
+ |value | -> 1 (value.u32)
+ +------+
+
+ DESC0 +------+
+ +-|addr | -> 0
+ | +------+
+ | |length| -> 1
+ | +------+
+ | |id | -> 3
+ | +------+
+ | |flags | -> VIRTIO_OF_DESC_F_WRITE
+ | +------+
+ |
+ DATA |>+------+ -> 0
+ |......|
+ +------+ -> 1
+\end{lstlisting}
+
+Note that the target is allowed to write the remote address of DESC3 and
+response Completion only in this example.
+
\subsubsection{Commands Definition}\label{sec:Virtio Transport Options / Virtio Over Fabrics / Transmission Protocol / Commands Definition}
This section defines command structures for Virtio Over Fabrics.
@@ -751,6 +862,8 @@ \subsubsection{Opcodes Definition}\label{sec:Virtio Transport Options / Virtio O
\hline
virtio_of_feature_max_segment & 0x0 & Get the maximum segments within a Vring Command supported by target \\
\hline
+virtio_of_feature_stream_size & 0x1 & Get the target/set the initiator stream buffer size of a Command \\
+\hline
\end{tabular}
\paragraph{virtio_of_op_set_feature}\label{sec:Virtio Transport Options / Virtio Over Fabrics / Transmission Protocol / Opcodes Definition / virtio_of_op_set_feature}
--
2.25.1
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