4635c840ce
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 <ciara.power@intel.com> Acked-by: Kevin Laatz <kevin.laatz@intel.com>
37 lines
1.3 KiB
ReStructuredText
37 lines
1.3 KiB
ReStructuredText
.. SPDX-License-Identifier: BSD-3-Clause
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Copyright(c) 2020 Intel Corporation.
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Using AVX-512 with DPDK
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=======================
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AVX-512 is not used by default in DPDK, but it can be selected at runtime by apps through the use of EAL API,
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and by the user with a commandline argument. DPDK has a setting for max SIMD bitwidth,
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which can be modified and will then limit the vector path taken by the code.
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Using the API in apps
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---------------------
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Apps can request DPDK uses AVX-512 at runtime, if it provides improved application performance.
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This can be done by modifying the EAL setting for max SIMD bitwidth to 512, as by default it is 256,
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which does not allow for AVX-512.
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.. code-block:: c
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rte_vect_set_max_simd_bitwidth(RTE_VECT_SIMD_512);
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This API should only be called once at initialization, before EAL init.
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For more information on the possible enum values to use as a parameter, go to :ref:`max_simd_bitwidth`:
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Using the command-line argument
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---------------------------------------------
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The user can select to use AVX-512 at runtime, using the following argument to set the max bitwidth::
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./app/dpdk-testpmd --force-max-simd-bitwidth=512
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This will override any further changes to the max SIMD bitwidth in DPDK,
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which is useful for testing purposes.
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