-Please note that while using iommu=pt is compulsory for igb_uio driver, the vfio-pci driver can actually work with both iommu=pt and iommu=on.
-
-High Performance of Small Packets on 40G NIC
---------------------------------------------
-
-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_requ st_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
-
- CONFIG_RTE_PCI_EXTENDED_TAG
-
- CONFIG_RTE_PCI_MAX_READ_REQUEST_SIZE
-
-Use 16 Bytes RX Descriptor Size
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-As i40e PMD supports both 16 and 32 bytes RX descriptor sizes, and 16 bytes size can provide helps to high performance of small packets.
-Configuration of CONFIG_RTE_LIBRTE_I40E_16BYTE_RX_DESC in config files can be changed to use 16 bytes size RX descriptors.