-Enabling Extended Tag and Setting Max Read Request Size
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-PCI configurations of ``extended_tag`` and max _read_requ st_size have big impacts on performance of small packets on 40G NIC.
-Enabling extended_tag and setting ``max_read_request_size`` to small size such as 128 bytes provide great helps to high performance of small packets.
-
-* These can be done in some BIOS implementations.
-
-* For other BIOS implementations, PCI configurations can be changed by using command of ``setpci``, or special configurations in DPDK config file of ``common_linux``.
-
- * Bits 7:5 at address of 0xA8 of each PCI device is used for setting the max_read_request_size,
- and bit 8 of 0xA8 of each PCI device is used for enabling/disabling the extended_tag.
- lspci and setpci can be used to read the values of 0xA8 and then write it back after being changed.
-
- * In config file of common_linux, below three configurations can be changed for the same purpose.
-
- ``CONFIG_RTE_PCI_CONFIG``
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- ``CONFIG_RTE_PCI_EXTENDED_TAG``
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- ``CONFIG_RTE_PCI_MAX_READ_REQUEST_SIZE``
-
-* From release 16.04, ``extended_tag`` is enabled by default during port
- initialization, users don't need to care about that anymore.
-