[PATCH v9 17/17] doc: update multicore dispatch model in graph guides

[Jerin Jacob]

On Wed, Jun 7, 2023 at 9:30 AM Zhirun Yan <zhirun.yan at intel.com> wrote:
>
> Update graph documentation to introduce new multicore dispatch model.

Please squash this to relevant implementation patches, No need for
separate patch. This is the contribution guideline followed.

>
> Signed-off-by: Haiyue Wang <haiyue.wang at intel.com>
> Signed-off-by: Cunming Liang <cunming.liang at intel.com>
> Signed-off-by: Zhirun Yan <zhirun.yan at intel.com>
> ---
>  doc/guides/prog_guide/graph_lib.rst | 68 +++++++++++++++++++++++++++--
>  1 file changed, 64 insertions(+), 4 deletions(-)
>
> diff --git a/doc/guides/prog_guide/graph_lib.rst b/doc/guides/prog_guide/graph_lib.rst
> index 1cfdc86433..8c2c2816ed 100644
> --- a/doc/guides/prog_guide/graph_lib.rst
> +++ b/doc/guides/prog_guide/graph_lib.rst
> @@ -189,14 +189,74 @@ In the above example, A graph object will be created with ethdev Rx
>  node of port 0 and queue 0, all ipv4* nodes in the system,
>  and ethdev tx node of all ports.
>
> -Multicore graph processing
> -~~~~~~~~~~~~~~~~~~~~~~~~~~
> -In the current graph library implementation, specifically,
> -``rte_graph_walk()`` and ``rte_node_enqueue*`` fast path API functions
> +Graph models chossing

Graph models

> +~~~~~~~~~~~~~~~~~~~~~
> +Currently, there are 2 different walking models. Use macro
> +RTE_GRAPH_MODEL_SELECT to set the model in compile time. Also offers the
> +ability to choose models in runtime

by not defining RTE_GRAPH_MODEL_SELECT.

> +For application, must #define RTE_GRAPH_MODEL_SELECT before including
> +rte_graph_worker.h

Some rewording as suggestion.

Graph models
~~~~~~~~~~~~
There are two different kinds of graph walking models. User can select
the model using
``rte_graph_worker_model_set()`` API. If the application decides to
use only one model,
 the fast path check can be avoided by defining the model with
RTE_GRAPH_MODEL_SELECT. For example:

.. code-block:: console

#define RTE_GRAPH_MODEL_SELECT RTE_GRAPH_MODEL_RTC
#include "rte_graph_worker.h"



> +
> +In l3fwd-graph, set RTE_GRAPH_MODEL_SELECT as the model explicitly for
> +performance-sensitive use case.
> +Or set the macro as GRAPH_MODEL_MCORE_RUNTIME_SELECT. And parse
> +``"--model=NAME"`` in cmdline and use ``rte_graph_worker_model_set()``
> +to set the walking model in runtime.

Please move to doc/guides/sample_app_ug/l3_forward_graph.rst

> +
> +RTC (Run-To-Completion)
> +^^^^^^^^^^^^^^^^^^^^^^^
> +This is the default graph walking model. Specifically,
> +``rte_graph_walk_rtc()`` and ``rte_node_enqueue*`` fast path API functions
>  are designed to work on single-core to have better performance.
>  The fast path API works on graph object, So the multi-core graph
>  processing strategy would be to create graph object PER WORKER.
>
> +Example:
> +
> +Graph: node-0 -> node-1 -> node-2 @Core0.
> +
> +.. code-block:: diff
> +
> +    + - - - - - - - - - - - - - - - - - - - - - +
> +    '                  Core #0                  '
> +    '                                           '
> +    ' +--------+     +---------+     +--------+ '
> +    ' | Node-0 | --> | Node-1  | --> | Node-2 | '
> +    ' +--------+     +---------+     +--------+ '
> +    '                                           '
> +    + - - - - - - - - - - - - - - - - - - - - - +
> +
> +Dispatch model
> +^^^^^^^^^^^^^^
> +The dispatch model enables a cross-core dispatching mechanism which employs
> +a scheduling work-queue to dispatch streams to other worker cores which
> +being associated with the destination node.
> +
> +Use ``rte_graph_model_mcore_dispatch_lcore_affinity_set()`` to set lcore affinity
> +with the node.
> +Each worker core will have a graph repetition. Use ``rte_graph_clone()`` to clone
> +graph for each worker and use``rte_graph_model_mcore_dispatch_core_bind()`` to
> +bind graph with the worker core.
> +
> +Example:
> +
> +Graph topo: node-0 -> Core1; node-1 -> node-2; node-2 -> node-3.
> +Config graph: node-0 @Core0; node-1/3 @Core1; node-2 @Core2.
> +
> +.. code-block:: diff
> +
> +    + - - - - - -+     +- - - - - - - - - - - - - +     + - - - - - -+
> +    '  Core #0   '     '          Core #1         '     '  Core #2   '
> +    '            '     '                          '     '            '
> +    ' +--------+ '     ' +--------+    +--------+ '     ' +--------+ '
> +    ' | Node-0 | - - - ->| Node-1 |    | Node-3 |<- - - - | Node-2 | '
> +    ' +--------+ '     ' +--------+    +--------+ '     ' +--------+ '
> +    '            '     '     |                    '     '      ^     '
> +    + - - - - - -+     +- - -|- - - - - - - - - - +     + - - -|- - -+
> +                             |                                 |
> +                             + - - - - - - - - - - - - - - - - +
> +
> +
>  In fast path
>  ~~~~~~~~~~~~
>  Typical fast-path code looks like below, where the application
> --
> 2.37.2
>