Re: [dpdk-dev] [PATCH] doc: fix guide for DLB v2.5

[David Marchand <david.marchand@redhat.com>]

On Sat, May 15, 2021 at 7:29 PM Timothy McDaniel
<timothy.mcdaniel@intel.com> wrote:
>
> - Remove references to deferred scheduling. That feature applies
>   to DLB v1.0 only.
> - Replace vdev references with the pci devargs equivalent
> - Add section for new "vector_opts_enabled" devarg
>
> Fixes: 7c6cc633fc7d ("doc: update guide for DLB v2.5")
> Cc: timothy.mcdaniel@intel.com
>
> Signed-off-by: Timothy McDaniel <timothy.mcdaniel@intel.com>
> ---
>  doc/guides/eventdevs/dlb2.rst | 54 +++++++++++++++--------------------
>  1 file changed, 23 insertions(+), 31 deletions(-)
>
> diff --git a/doc/guides/eventdevs/dlb2.rst b/doc/guides/eventdevs/dlb2.rst
> index 31de6bc47..bce984ca0 100644
> --- a/doc/guides/eventdevs/dlb2.rst
> +++ b/doc/guides/eventdevs/dlb2.rst
> @@ -152,19 +152,19 @@ These pools' sizes are controlled by the nb_events_limit field in struct
>  rte_event_dev_config. The load-balanced pool is sized to contain
>  nb_events_limit credits, and the directed pool is sized to contain
>  nb_events_limit/4 credits. The directed pool size can be overridden with the
> -num_dir_credits vdev argument, like so:
> +num_dir_credits devargs argument, like so:
>
>      .. code-block:: console
>
> -       --vdev=dlb2_event,num_dir_credits=<value>
> +       --allow ea:00.0,num_dir_credits=<value>
>
>  This can be used if the default allocation is too low or too high for the
> -specific application needs. The PMD also supports a vdev arg that limits the
> +specific application needs. The PMD also supports a devarg that limits the
>  max_num_events reported by rte_event_dev_info_get():
>
>      .. code-block:: console
>
> -       --vdev=dlb2_event,max_num_events=<value>
> +       --allow ea:00.0,max_num_events=<value>
>
>  By default, max_num_events is reported as the total available load-balanced
>  credits. If multiple DLB-based applications are being used, it may be desirable
> @@ -293,27 +293,6 @@ The PMD does not support the following configuration sequences:
>  This sequence is not supported because the event device must be reconfigured
>  before its ports or queues can be.
>
> -Deferred Scheduling
> -~~~~~~~~~~~~~~~~~~~
> -
> -The DLB PMD's default behavior for managing a CQ is to "pop" the CQ once per
> -dequeued event before returning from rte_event_dequeue_burst(). This frees the
> -corresponding entries in the CQ, which enables the DLB to schedule more events
> -to it.
> -
> -To support applications seeking finer-grained scheduling control -- for example
> -deferring scheduling to get the best possible priority scheduling and
> -load-balancing -- the PMD supports a deferred scheduling mode. In this mode,
> -the CQ entry is not popped until the *subsequent* rte_event_dequeue_burst()
> -call. This mode only applies to load-balanced event ports with dequeue depth of
> -1.
> -
> -To enable deferred scheduling, use the defer_sched vdev argument like so:
> -
> -    .. code-block:: console
> -
> -       --vdev=dlb2_event,defer_sched=on
> -
>  Atomic Inflights Allocation
>  ~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> @@ -336,11 +315,11 @@ buffer space (e.g. if not all queues are used, or aren't used for atomic
>  scheduling).
>
>  The PMD provides a dev arg to override the default per-queue allocation. To
> -increase a vdev's per-queue atomic-inflight allocation to (for example) 64:
> +increase per-queue atomic-inflight allocation to (for example) 64:
>
>      .. code-block:: console
>
> -       --vdev=dlb2_event,atm_inflights=64
> +       --allow ea:00.0,atm_inflights=64
>
>  QID Depth Threshold
>  ~~~~~~~~~~~~~~~~~~~
> @@ -363,9 +342,9 @@ shown below.
>
>      .. code-block:: console
>
> -       --vdev=dlb2_event,qid_depth_thresh=all:<threshold_value>
> -       --vdev=dlb2_event,qid_depth_thresh=qidA-qidB:<threshold_value>
> -       --vdev=dlb2_event,qid_depth_thresh=qid:<threshold_value>
> +       --allow ea:00.0,qid_depth_thresh=all:<threshold_value>
> +       --allow ea:00.0,qid_depth_thresh=qidA-qidB:<threshold_value>
> +       --allow ea:00.0,qid_depth_thresh=qid:<threshold_value>

Did you try this syntax?
The previous syntax with vdev did not work, and the new one probably
won't either.
Only the first devargs will be passed to the driver.

Example with the null pmd:
$ ./build/app/dpdk-testpmd -m 512 --no-huge --log-level=*:debug --vdev
net_null,copy=1 --vdev net_null,size=1024 -- -ia
--total-num-mbufs=2048
...
vdev_probe_all_drivers(): Search driver to probe device net_null
rte_pmd_null_probe(): Initializing pmd_null for net_null
rte_pmd_null_probe(): Configure pmd_null: packet size is 64, packet
copy is enabled
                                                         ^^
     ^^^^^^^
eth_dev_null_create(): Creating null ethdev on numa socket 0
...


If you want to pass multiple options for a single device, pass them all at once.
Like:
--allow ea:00.0,qid_depth_thresh=all:<threshold_value>,qid_depth_thresh=qidA-qidB:<threshold_value>,qid_depth_thresh=qid:<threshold_value>

>
>  Class of service
>  ~~~~~~~~~~~~~~~~
> @@ -387,4 +366,17 @@ Class of service can be specified in the devargs, as follows
>
>      .. code-block:: console
>
> -       --vdev=dlb2_event,cos=<0..4>
> +       --allow ea:00.0,cos=<0..4>
> +
> +Use X86 Vector Instructions
> +~~~~~~~~~~~~~~~~~~~~~~~~~~~
> +
> +DLB supports using x86 vector instructions to optimize the data path.
> +
> +The default mode of operation is to use scalar instructions, but
> +the use of vector instructions can be enabled in the devargs, as
> +follows
> +
> +    .. code-block:: console
> +
> +       --allow ea:00.0,vector_opts_enabled=<y/Y>

This option does not exist.
All I see is:
drivers/event/dlb2/dlb2_priv.h:#define DLB2_VECTOR_OPTS_DISAB_ARG
"vector_opts_disable"

What of --force-max-simd-bitwidth ?


-- 
David Marchand