[ovs-dev] [v12 09/16] docs/dpdk/bridge: Add dpif performance section.

Stokes, Ian ian.stokes at intel.com
Wed Jun 2 18:40:33 UTC 2021


> This section details how two new commands can be used to list and select
> the different dpif implementations. It also details how a non default
> dpif implementation can be tested with the OVS unit test suite.
> 
> Add NEWS updates for the dpif-netdev.c refactor and the new dpif
> implementations/commands.
> 
> Signed-off-by: Cian Ferriter <cian.ferriter at intel.com>

Thanks for the patch Cian, some comments inline below.

One thing to flag is that for reviewing this is fine as a commit on it's own focusing on updating the documentation.

But I think it would be better to split this patch among the previous patches and update the documentation as features are added, code refactored etc. in the code base.

That way the documentation is an accurate reflection of the codebase at that particular commit for each change. Does this make sense?

> 
> ---
> 
> v8:
> - Merge NEWS file items into one Userspace Datapath: heading
> ---
>  Documentation/topics/dpdk/bridge.rst | 37
> ++++++++++++++++++++++++++++
>  NEWS                                 |  4 +++
>  2 files changed, 41 insertions(+)
> 
> diff --git a/Documentation/topics/dpdk/bridge.rst
> b/Documentation/topics/dpdk/bridge.rst
> index 526d5c959..ca90d7bdb 100644
> --- a/Documentation/topics/dpdk/bridge.rst
> +++ b/Documentation/topics/dpdk/bridge.rst
> @@ -214,3 +214,40 @@ implementation ::
> 
>  Compile OVS in debug mode to have `ovs_assert` statements error out if
>  there is a mis-match in the DPCLS lookup implementation.
> +
> +Datapath Interface Performance
> +------------------------------
> +
> +The datapath interface (DPIF) or dp_netdev_input() is responsible for
> taking
> +packets through the major components of the userspace datapath; such as
> +miniflow_extract, EMC, SMC and DPCLS lookups, and a lot of the
> performance
> +stats associated with the datapath.
> +
> +Just like with the SIMD DPCLS work above, SIMD can be applied to the DPIF

Minor, would replace "work" with "feature".

> to
> +improve performance.
> +
> +OVS provides multiple implementations of the DPIF. These can be listed
> with the
> +following command ::
> +
> +    $ ovs-appctl dpif-netdev/dpif-get
> +    Available DPIF implementations:
> +      dpif_scalar
> +      dpif_avx512
> +
> +By default, dpif_scalar is used. The DPIF implementation can be selected by
> +name ::
> +
> +    $ ovs-appctl dpif-netdev/dpif-set dpif_avx512
> +    DPIF implementation set to dpif_avx512.
> +
> +    $ ovs-appctl dpif-netdev/dpif-set dpif_scalar
> +    DPIF implementation set to dpif_scalar.
> +

Maybe this is later in the series but have you given consideration to updating the man pages for these dpif-netdev commands also?

> +Running Unit Tests with AVX512 DPIF
> +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> +
> +Since the AVX512 DPIF is disabled by default, a compile time option is
> +available in order to test it with the OVS unit test suite. When building with
> +a CPU that supports AVX512, use the following configure option ::
> +
> +    $ ./configure --enable-dpif-default-avx512

Would it be useful to provide the log output the user would expect to see during configuration to confirm AVX512 DPIF is in use?

> diff --git a/NEWS b/NEWS
> index 3eab5f4fa..5e847a95e 100644
> --- a/NEWS
> +++ b/NEWS
> @@ -7,6 +7,10 @@ Post-v2.15.0
>         cases, e.g if all PMD threads are running on the same NUMA node.
>       * Add a partial HWOL PMD statistic counting hits similar to existing
>       * EMC/SMC/DPCLS stats.
> +     * Refactor lib/dpif-netdev.c to multiple header files.
> +     * Add avx512 implementation of dpif which can process non recirculated
> +       packets. It supports partial HWOL, EMC, SMC and DPCLS lookups.
> +     * Add commands to get and set the dpif implementations.

As flagged above these news entries could be split into the previous patches that made those changes.

Thanks
Ian
>     - ovs-ctl:
>       * New option '--no-record-hostname' to disable hostname configuration
>         in ovsdb on startup.
> --
> 2.31.1
> 
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