From 4635c840ce48f8c6670774e4dda3a24c68d3d745 Mon Sep 17 00:00:00 2001 From: Ciara Power Date: Mon, 19 Oct 2020 15:48:42 +0200 Subject: [PATCH] doc: describe how to enable AVX512 This patch adds documentation on the usage of the max SIMD bitwidth EAL setting to enable AVX-512 at runtime. Signed-off-by: Ciara Power Acked-by: Kevin Laatz --- doc/guides/howto/avx512.rst | 36 ++++++++++++++++++++++++++++++++++++ doc/guides/howto/index.rst | 1 + 2 files changed, 37 insertions(+) create mode 100644 doc/guides/howto/avx512.rst diff --git a/doc/guides/howto/avx512.rst b/doc/guides/howto/avx512.rst new file mode 100644 index 0000000000..6c034b617d --- /dev/null +++ b/doc/guides/howto/avx512.rst @@ -0,0 +1,36 @@ +.. SPDX-License-Identifier: BSD-3-Clause + Copyright(c) 2020 Intel Corporation. + + +Using AVX-512 with DPDK +======================= + +AVX-512 is not used by default in DPDK, but it can be selected at runtime by apps through the use of EAL API, +and by the user with a commandline argument. DPDK has a setting for max SIMD bitwidth, +which can be modified and will then limit the vector path taken by the code. + + +Using the API in apps +--------------------- + +Apps can request DPDK uses AVX-512 at runtime, if it provides improved application performance. +This can be done by modifying the EAL setting for max SIMD bitwidth to 512, as by default it is 256, +which does not allow for AVX-512. + +.. code-block:: c + + rte_vect_set_max_simd_bitwidth(RTE_VECT_SIMD_512); + +This API should only be called once at initialization, before EAL init. +For more information on the possible enum values to use as a parameter, go to :ref:`max_simd_bitwidth`: + + +Using the command-line argument +--------------------------------------------- + +The user can select to use AVX-512 at runtime, using the following argument to set the max bitwidth:: + + ./app/dpdk-testpmd --force-max-simd-bitwidth=512 + +This will override any further changes to the max SIMD bitwidth in DPDK, +which is useful for testing purposes. diff --git a/doc/guides/howto/index.rst b/doc/guides/howto/index.rst index 5a97ea508c..c2a2c60ddb 100644 --- a/doc/guides/howto/index.rst +++ b/doc/guides/howto/index.rst @@ -20,3 +20,4 @@ HowTo Guides telemetry debug_troubleshoot openwrt + avx512 -- 2.20.1