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When the VLAN tag is present in the packet buffer (i.e VLAN stripping disabled, QinQ) the driver will currently report CHECKSUM_UNNECESSARY. Instead of using CHECKSUM_COMPLETE offload for packets with first ethertype of IPv4/6, use it for packets with last ethertype of IPv4/6 to cover the former cases as well. The checksum field present in the CQE is calculated from the IP header until the end of the packet. When the first ethertype is different than IPv4/6 (for ex. 802.1Q VLAN) a checksum of the VLAN header/s should be added. The small header/s checksum calculation will allow us to use CHECKSUM_COMPLETE instead of CHECKSUM_UNNECESSARY. Testing bandwidth of one and 8 TCP streams to a single RQ, LRO and VLAN stripping offloads disabled: CPU: Intel(R) Xeon(R) CPU E5-2660 v2 @ 2.20GHz NIC: Mellanox Technologies MT27710 Family [ConnectX-4 Lx] Before: +--------------+--------------------+---------------------+----------------------+ | Traffic type | 1 Stream BW [Mbps] | 8 Streams BW [Mbps] | Checksum offload | +--------------+--------------------+---------------------+----------------------+ | Untagged | 28,247.35 | 24,716.88 | CHECKSUM_COMPLETE | | VLAN | 27,516.69 | 23,752.26 | CHECKSUM_UNNECESSARY | | QinQ | 6,961.30 | 20,667.04 | CHECKSUM_UNNECESSARY | +--------------+--------------------+---------------------+----------------------+ Now: +--------------+--------------------+---------------------+-------------------+ | Traffic type | 1 Stream BW [Mbps] | 8 Streams BW [Mbps] | Checksum offload | +--------------+--------------------+---------------------+-------------------+ | Untagged | 28,521.28 | 24,926.32 | CHECKSUM_COMPLETE | | VLAN | 27,389.37 | 23,715.34 | CHECKSUM_COMPLETE | | QinQ | 6,901.77 | 20,845.73 | CHECKSUM_COMPLETE | +--------------+--------------------+---------------------+-------------------+ No performance degradation observed. Signed-off-by: Gal Pressman <galp@mellanox.com> Reviewed-by: Tariq Toukan <tariqt@mellanox.com> Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.