- A nonzero value enables multi-packet send (MPS) for ConnectX-4 Lx and
- enhanced multi-packet send (Enhanced MPS) for ConnectX-5 and Bluefield.
- MPS allows the TX burst function to pack up multiple packets in a
- single descriptor session in order to save PCI bandwidth and improve
- performance at the cost of a slightly higher CPU usage. When
- ``txq_inline`` is set along with ``txq_mpw_en``, TX burst function tries
- to copy entire packet data on to TX descriptor instead of including
- pointer of packet only if there is enough room remained in the
- descriptor. ``txq_inline`` sets per-descriptor space for either pointers
- or inlined packets. In addition, Enhanced MPS supports hybrid mode -
- mixing inlined packets and pointers in the same descriptor.
-
- This option cannot be used with certain offloads such as ``DEV_TX_OFFLOAD_TCP_TSO,
- DEV_TX_OFFLOAD_VXLAN_TNL_TSO, DEV_TX_OFFLOAD_GRE_TNL_TSO, DEV_TX_OFFLOAD_VLAN_INSERT``.
- When those offloads are requested the MPS send function will not be used.
-
- It is currently only supported on the ConnectX-4 Lx, ConnectX-5 and Bluefield
- families of adapters. Enabled by default.
+ If inline data are enabled it may affect the maximal size of Tx queue in
+ descriptors because the inline data increase the descriptor size and
+ queue size limits supported by hardware may be exceeded.
+
+- ``txq_inline_min`` parameter [int]
+
+ Minimal amount of data to be inlined into WQE during Tx operations. NICs
+ may require this minimal data amount to operate correctly. The exact value
+ may depend on NIC operation mode, requested offloads, etc. It is strongly
+ recommended to omit this parameter and use the default values. Anyway,
+ applications using this parameter should take into consideration that
+ specifying an inconsistent value may prevent the NIC from sending packets.
+
+ If ``txq_inline_min`` key is present the specified value (may be aligned
+ by the driver in order not to exceed the limits and provide better descriptor
+ space utilization) will be used by the driver and it is guaranteed that
+ requested amount of data bytes are inlined into the WQE beside other inline
+ settings. This key also may update ``txq_inline_max`` value (default
+ or specified explicitly in devargs) to reserve the space for inline data.
+
+ If ``txq_inline_min`` key is not present, the value may be queried by the
+ driver from the NIC via DevX if this feature is available. If there is no DevX
+ enabled/supported the value 18 (supposing L2 header including VLAN) is set
+ for ConnectX-4 and ConnectX-4LX, and 0 is set by default for ConnectX-5
+ and newer NICs. If packet is shorter the ``txq_inline_min`` value, the entire
+ packet is inlined.
+
+ For ConnectX-4 NIC, driver does not allow specifying value below 18
+ (minimal L2 header, including VLAN), error will be raised.
+
+ For ConnectX-4LX NIC, it is allowed to specify values below 18, but
+ it is not recommended and may prevent NIC from sending packets over
+ some configurations.
+
+ Please, note, this minimal data inlining disengages eMPW feature (Enhanced
+ Multi-Packet Write), because last one does not support partial packet inlining.
+ This is not very critical due to minimal data inlining is mostly required
+ by ConnectX-4 and ConnectX-4 Lx, these NICs do not support eMPW feature.
+
+- ``txq_inline_max`` parameter [int]
+
+ Specifies the maximal packet length to be completely inlined into WQE
+ Ethernet Segment for ordinary SEND method. If packet is larger than specified
+ value, the packet data won't be copied by the driver at all, data buffer
+ is addressed with a pointer. If packet length is less or equal all packet
+ data will be copied into WQE. This may improve PCI bandwidth utilization for
+ short packets significantly but requires the extra CPU cycles.
+
+ The data inline feature is controlled by number of Tx queues, if number of Tx
+ queues is larger than ``txqs_min_inline`` key parameter, the inline feature
+ is engaged, if there are not enough Tx queues (which means not enough CPU cores
+ and CPU resources are scarce), data inline is not performed by the driver.
+ Assigning ``txqs_min_inline`` with zero always enables the data inline.
+
+ The default ``txq_inline_max`` value is 290. The specified value may be adjusted
+ by the driver in order not to exceed the limit (930 bytes) and to provide better
+ WQE space filling without gaps, the adjustment is reflected in the debug log.
+ Also, the default value (290) may be decreased in run-time if the large transmit
+ queue size is requested and hardware does not support enough descriptor
+ amount, in this case warning is emitted. If ``txq_inline_max`` key is
+ specified and requested inline settings can not be satisfied then error
+ will be raised.
+
+- ``txq_inline_mpw`` parameter [int]
+
+ Specifies the maximal packet length to be completely inlined into WQE for
+ Enhanced MPW method. If packet is large the specified value, the packet data
+ won't be copied, and data buffer is addressed with pointer. If packet length
+ is less or equal, all packet data will be copied into WQE. This may improve PCI
+ bandwidth utilization for short packets significantly but requires the extra
+ CPU cycles.
+
+ The data inline feature is controlled by number of TX queues, if number of Tx
+ queues is larger than ``txqs_min_inline`` key parameter, the inline feature
+ is engaged, if there are not enough Tx queues (which means not enough CPU cores
+ and CPU resources are scarce), data inline is not performed by the driver.
+ Assigning ``txqs_min_inline`` with zero always enables the data inline.
+
+ The default ``txq_inline_mpw`` value is 268. The specified value may be adjusted
+ by the driver in order not to exceed the limit (930 bytes) and to provide better
+ WQE space filling without gaps, the adjustment is reflected in the debug log.
+ Due to multiple packets may be included to the same WQE with Enhanced Multi
+ Packet Write Method and overall WQE size is limited it is not recommended to
+ specify large values for the ``txq_inline_mpw``. Also, the default value (268)
+ may be decreased in run-time if the large transmit queue size is requested
+ and hardware does not support enough descriptor amount, in this case warning
+ is emitted. If ``txq_inline_mpw`` key is specified and requested inline
+ settings can not be satisfied then error will be raised.
+
+- ``txqs_max_vec`` parameter [int]
+
+ Enable vectorized Tx only when the number of TX queues is less than or
+ equal to this value. This parameter is deprecated and ignored, kept
+ for compatibility issue to not prevent driver from probing.