40. NVIDIA MLX5 Ethernet Driver

Note

NVIDIA acquired Mellanox Technologies in 2020. The DPDK documentation and code might still include instances of or references to Mellanox trademarks (like BlueField and ConnectX) that are now NVIDIA trademarks.

The mlx5 Ethernet poll mode driver library (librte_net_mlx5) provides support for NVIDIA ConnectX-4, NVIDIA ConnectX-4 Lx , NVIDIA ConnectX-5, NVIDIA ConnectX-6, NVIDIA ConnectX-6 Dx, NVIDIA ConnectX-6 Lx, NVIDIA ConnectX-7, NVIDIA BlueField, NVIDIA BlueField-2 and NVIDIA BlueField-3 families of 10/25/40/50/100/200/400 Gb/s adapters as well as their virtual functions (VF) in SR-IOV context.

40.1. Supported NICs

The following NVIDIA device families are supported by the same mlx5 driver:

  • ConnectX-4
  • ConnectX-4 Lx
  • ConnectX-5
  • ConnectX-5 Ex
  • ConnectX-6
  • ConnectX-6 Dx
  • ConnectX-6 Lx
  • ConnectX-7
  • BlueField
  • BlueField-2
  • BlueField-3

Below are detailed device names:

  • NVIDIA® ConnectX®-4 10G MCX4111A-XCAT (1x10G)
  • NVIDIA® ConnectX®-4 10G MCX412A-XCAT (2x10G)
  • NVIDIA® ConnectX®-4 25G MCX4111A-ACAT (1x25G)
  • NVIDIA® ConnectX®-4 25G MCX412A-ACAT (2x25G)
  • NVIDIA® ConnectX®-4 40G MCX413A-BCAT (1x40G)
  • NVIDIA® ConnectX®-4 40G MCX4131A-BCAT (1x40G)
  • NVIDIA® ConnectX®-4 40G MCX415A-BCAT (1x40G)
  • NVIDIA® ConnectX®-4 50G MCX413A-GCAT (1x50G)
  • NVIDIA® ConnectX®-4 50G MCX4131A-GCAT (1x50G)
  • NVIDIA® ConnectX®-4 50G MCX414A-BCAT (2x50G)
  • NVIDIA® ConnectX®-4 50G MCX415A-GCAT (1x50G)
  • NVIDIA® ConnectX®-4 50G MCX416A-BCAT (2x50G)
  • NVIDIA® ConnectX®-4 50G MCX416A-GCAT (2x50G)
  • NVIDIA® ConnectX®-4 50G MCX415A-CCAT (1x100G)
  • NVIDIA® ConnectX®-4 100G MCX416A-CCAT (2x100G)
  • NVIDIA® ConnectX®-4 Lx 10G MCX4111A-XCAT (1x10G)
  • NVIDIA® ConnectX®-4 Lx 10G MCX4121A-XCAT (2x10G)
  • NVIDIA® ConnectX®-4 Lx 25G MCX4111A-ACAT (1x25G)
  • NVIDIA® ConnectX®-4 Lx 25G MCX4121A-ACAT (2x25G)
  • NVIDIA® ConnectX®-4 Lx 40G MCX4131A-BCAT (1x40G)
  • NVIDIA® ConnectX®-5 100G MCX556A-ECAT (2x100G)
  • NVIDIA® ConnectX®-5 Ex EN 100G MCX516A-CDAT (2x100G)
  • NVIDIA® ConnectX®-6 200G MCX654106A-HCAT (2x200G)
  • NVIDIA® ConnectX®-6 Dx EN 100G MCX623106AN-CDAT (2x100G)
  • NVIDIA® ConnectX®-6 Dx EN 200G MCX623105AN-VDAT (1x200G)
  • NVIDIA® ConnectX®-6 Lx EN 25G MCX631102AN-ADAT (2x25G)
  • NVIDIA® ConnectX®-7 200G CX713106AE-HEA_QP1_Ax (2x200G)
  • NVIDIA® BlueField®-2 25G MBF2H332A-AEEOT_A1 (2x25Gg
  • NVIDIA® BlueField®-3 200GbE 900-9D3B6-00CV-AA0 (2x200)
  • NVIDIA® BlueField®-3 200GbE 900-9D3B6-00SV-AA0 (2x200)
  • NVIDIA® BlueField®-3 400GbE 900-9D3B6-00CN-AB0 (2x400)
  • NVIDIA® BlueField®-3 100GbE 900-9D3B4-00CC-EA0 (2x100)
  • NVIDIA® BlueField®-3 100GbE 900-9D3B4-00SC-EA0 (2x100)
  • NVIDIA® BlueField®-3 400GbE 900-9D3B4-00EN-EA0 (1x100)

40.2. Design

Besides its dependency on libibverbs (that implies libmlx5 and associated kernel support), librte_net_mlx5 relies heavily on system calls for control operations such as querying/updating the MTU and flow control parameters.

This capability allows the PMD to coexist with kernel network interfaces which remain functional, although they stop receiving unicast packets as long as they share the same MAC address. This means legacy linux control tools (for example: ethtool, ifconfig and more) can operate on the same network interfaces that owned by the DPDK application.

See NVIDIA MLX5 Common Driver guide for more design details, including prerequisites installation.

40.3. Features

  • Multi arch support: x86_64, POWER8, ARMv8, i686.
  • Multiple TX and RX queues.
  • Shared Rx queue.
  • Rx queue delay drop.
  • Rx queue available descriptor threshold event.
  • Host shaper support.
  • Support steering for external Rx queue created outside the PMD.
  • Support for scattered TX frames.
  • Advanced support for scattered Rx frames with tunable buffer attributes.
  • IPv4, IPv6, TCPv4, TCPv6, UDPv4 and UDPv6 RSS on any number of queues.
  • RSS using different combinations of fields: L3 only, L4 only or both, and source only, destination only or both.
  • Several RSS hash keys, one for each flow type.
  • Default RSS operation with no hash key specification.
  • Symmetric RSS function.
  • Configurable RETA table.
  • Link flow control (pause frame).
  • Support for multiple MAC addresses.
  • VLAN filtering.
  • RX VLAN stripping.
  • TX VLAN insertion.
  • RX CRC stripping configuration.
  • TX mbuf fast free offload.
  • Promiscuous mode on PF and VF.
  • Multicast promiscuous mode on PF and VF.
  • Hardware checksum offloads.
  • Flow director (RTE_FDIR_MODE_PERFECT, RTE_FDIR_MODE_PERFECT_MAC_VLAN and RTE_ETH_FDIR_REJECT).
  • Flow API, including Flow isolated mode.
  • Multiple process.
  • KVM and VMware ESX SR-IOV modes are supported.
  • RSS hash result is supported.
  • Hardware TSO for generic IP or UDP tunnel, including VXLAN and GRE.
  • Hardware checksum Tx offload for generic IP or UDP tunnel, including VXLAN and GRE.
  • RX interrupts.
  • Statistics query including Basic, Extended and per queue.
  • Rx HW timestamp.
  • Tunnel types: VXLAN, L3 VXLAN, VXLAN-GPE, GRE, MPLSoGRE, MPLSoUDP, IP-in-IP, Geneve, GTP.
  • Tunnel HW offloads: packet type, inner/outer RSS, IP and UDP checksum verification.
  • NIC HW offloads: encapsulation (vxlan, gre, mplsoudp, mplsogre), NAT, routing, TTL increment/decrement, count, drop, mark. For details please see Supported hardware offloads.
  • Flow insertion rate of more then million flows per second, when using Direct Rules.
  • Support for multiple rte_flow groups.
  • Per packet no-inline hint flag to disable packet data copying into Tx descriptors.
  • Hardware LRO.
  • Hairpin.
  • Multiple-thread flow insertion.
  • Matching on IPv4 Internet Header Length (IHL).
  • Matching on IPv6 routing extension header.
  • Matching on GTP extension header with raw encap/decap action.
  • Matching on Geneve TLV option header with raw encap/decap action.
  • Matching on ESP header SPI field.
  • Matching on InfiniBand BTH.
  • Modify IPv4/IPv6 ECN field.
  • RSS support in sample action.
  • E-Switch mirroring and jump.
  • E-Switch mirroring and modify.
  • 21844 flow priorities for ingress or egress flow groups greater than 0 and for any transfer flow group.
  • Flow quota.
  • Flow metering, including meter policy API.
  • Flow meter hierarchy.
  • Flow meter mark.
  • Flow integrity offload API.
  • Connection tracking.
  • Sub-Function representors.
  • Sub-Function.
  • Matching on represented port.
  • Matching on aggregated affinity.

40.4. Limitations

  • Windows support:

    On Windows, the features are limited:

    • Promiscuous mode is not supported
    • The following rules are supported:
      • IPv4/UDP with CVLAN filtering
      • Unicast MAC filtering
    • Additional rules are supported from WinOF2 version 2.70:
      • IPv4/TCP with CVLAN filtering
      • L4 steering rules for port RSS of UDP, TCP and IP

  • For secondary process:

    • Forked secondary process not supported.
    • MPRQ is not supported. Callback to free externally attached MPRQ buffer is set in a primary process, but has a different virtual address in a secondary process. Calling a function at the wrong address leads to a segmentation fault.
    • External memory unregistered in EAL memseg list cannot be used for DMA unless such memory has been registered by mlx5_mr_update_ext_mp() in primary process and remapped to the same virtual address in secondary process. If the external memory is registered by primary process but has different virtual address in secondary process, unexpected error may happen.

  • Shared Rx queue:

    • Counters of received packets and bytes number of devices in same share group are same.
    • Counters of received packets and bytes number of queues in same group and queue ID are same.

  • Available descriptor threshold event:

    • Does not support shared Rx queue and hairpin Rx queue.

  • The symmetric RSS function is supported by swapping source and destination addresses and ports.

  • Host shaper:

    • Support BlueField series NIC from BlueField-2.
    • When configuring host shaper with MLX5_HOST_SHAPER_FLAG_AVAIL_THRESH_TRIGGERED flag set, only rates 0 and 100Mbps are supported.

  • HW steering:

    • WQE based high scaling and safer flow insertion/destruction.

    • Set dv_flow_en to 2 in order to enable HW steering.

    • Async queue-based rte_flow_async APIs supported only.

    • NIC ConnectX-5 and before are not supported.

    • Reconfiguring flow API engine is not supported. Any subsequent call to rte_flow_configure() with different configuration than initially provided will be rejected with -ENOTSUP error code.

    • Partial match with item template is not supported.

    • IPv6 5-tuple matching is not supported.

    • With E-Switch enabled, ports which share the E-Switch domain should be started and stopped in a specific order:

      • When starting ports, the transfer proxy port should be started first and port representors should follow.
      • When stopping ports, all of the port representors should be stopped before stopping the transfer proxy port.

      If ports are started/stopped in an incorrect order, rte_eth_dev_start()/rte_eth_dev_stop() will return an appropriate error code:

      • -EAGAIN for rte_eth_dev_start().
      • -EBUSY for rte_eth_dev_stop().

    • Matching on ICMP6 following IPv6 routing extension header, should match ipv6_routing_ext_next_hdr instead of ICMP6.

  • When using Verbs flow engine (dv_flow_en = 0), flow pattern without any specific VLAN will match for VLAN packets as well:

    When VLAN spec is not specified in the pattern, the matching rule will be created with VLAN as a wild card. Meaning, the flow rule:

    flow create 0 ingress pattern eth / vlan vid is 3 / ipv4 / end ...

    Will only match vlan packets with vid=3. and the flow rule:

    flow create 0 ingress pattern eth / ipv4 / end ...

    Will match any ipv4 packet (VLAN included).

  • When using Verbs flow engine (dv_flow_en = 0), multi-tagged(QinQ) match is not supported.

  • When using DV flow engine (dv_flow_en = 1), flow pattern with any VLAN specification will match only single-tagged packets unless the ETH item type field is 0x88A8 or the VLAN item has_more_vlan field is 1. The flow rule:

    flow create 0 ingress pattern eth / ipv4 / end ...

    Will match any ipv4 packet. The flow rules:

    flow create 0 ingress pattern eth / vlan / end ...
flow create 0 ingress pattern eth has_vlan is 1 / end ...
flow create 0 ingress pattern eth type is 0x8100 / end ...

    Will match single-tagged packets only, with any VLAN ID value. The flow rules:

    flow create 0 ingress pattern eth type is 0x88A8 / end ...
flow create 0 ingress pattern eth / vlan has_more_vlan is 1 / end ...

    Will match multi-tagged packets only, with any VLAN ID value.

  • A flow pattern with 2 sequential VLAN items is not supported.

  • VLAN pop offload command:

    • Flow rules having a VLAN pop offload command as one of their actions and are lacking a match on VLAN as one of their items are not supported.
    • The command is not supported on egress traffic in NIC mode.

  • VLAN push offload is not supported on ingress traffic in NIC mode.

  • VLAN set PCP offload is not supported on existing headers.

  • A multi segment packet must have not more segments than reported by dev_infos_get() in tx_desc_lim.nb_seg_max field. This value depends on maximal supported Tx descriptor size and txq_inline_min settings and may be from 2 (worst case forced by maximal inline settings) to 58.

  • Match on VXLAN supports the following fields only:

    • VNI
    • Last reserved 8-bits

    Last reserved 8-bits matching is only supported When using DV flow engine (dv_flow_en = 1). For ConnectX-5, the UDP destination port must be the standard one (4789). Group zero’s behavior may differ which depends on FW. Matching value equals 0 (value & mask) is not supported.

  • L3 VXLAN and VXLAN-GPE tunnels cannot be supported together with MPLSoGRE and MPLSoUDP.

  • MPLSoGRE is not supported in HW steering (dv_flow_en = 2).

  • MPLSoUDP with multiple MPLS headers is only supported in HW steering (dv_flow_en = 2).

  • Match on Geneve header supports the following fields only:

    • VNI
    • OAM
    • protocol type
    • options length

  • Match on Geneve TLV option is supported on the following fields:

    • Class
    • Type
    • Length
    • Data

    Only one Class/Type/Length Geneve TLV option is supported per shared device. Class/Type/Length fields must be specified as well as masks. Class/Type/Length specified masks must be full. Matching Geneve TLV option without specifying data is not supported. Matching Geneve TLV option with data & mask == 0 is not supported.

  • VF: flow rules created on VF devices can only match traffic targeted at the configured MAC addresses (see rte_eth_dev_mac_addr_add()).

  • Match on GTP tunnel header item supports the following fields only:

    • v_pt_rsv_flags: E flag, S flag, PN flag
    • msg_type
    • teid

  • Match on GTP extension header only for GTP PDU session container (next extension header type = 0x85).

  • Match on GTP extension header is not supported in group 0.

  • When using DV/Verbs flow engine (dv_flow_en = 1/0 respectively), match on SPI field in ESP header for group 0 is supported from ConnectX-7.

  • Matching on SPI field in ESP header is supported over the PF only.

  • Flex item:

    • Hardware support: NVIDIA BlueField-2 and NVIDIA BlueField-3.
    • Flex item is supported on PF only.
    • Hardware limits header_length_mask_width up to 6 bits.
    • Firmware supports 8 global sample fields. Each flex item allocates non-shared sample fields from that pool.
    • Supported flex item can have 1 input link - eth or udp and up to 3 output links - ipv4 or ipv6.
    • Flex item fields (next_header, next_protocol, samples) do not participate in RSS hash functions.
    • In flex item configuration, next_header.field_base value must be byte aligned (multiple of 8).
    • Modify field with flex item, the offset must be byte aligned (multiple of 8).

  • No Tx metadata go to the E-Switch steering domain for the Flow group 0. The flows within group 0 and set metadata action are rejected by hardware.

Note

MAC addresses not already present in the bridge table of the associated kernel network device will be added and cleaned up by the PMD when closing the device. In case of ungraceful program termination, some entries may remain present and should be removed manually by other means.

  • Buffer split offload is supported with regular Rx burst routine only, no MPRQ feature or vectorized code can be engaged.

  • When Multi-Packet Rx queue is configured (mprq_en), a Rx packet can be externally attached to a user-provided mbuf with having RTE_MBUF_F_EXTERNAL in ol_flags. As the mempool for the external buffer is managed by PMD, all the Rx mbufs must be freed before the device is closed. Otherwise, the mempool of the external buffers will be freed by PMD and the application which still holds the external buffers may be corrupted. User-managed mempools with external pinned data buffers cannot be used in conjunction with MPRQ since packets may be already attached to PMD-managed external buffers.

  • If Multi-Packet Rx queue is configured (mprq_en) and Rx CQE compression is enabled (rxq_cqe_comp_en) at the same time, RSS hash result is not fully supported. Some Rx packets may not have RTE_MBUF_F_RX_RSS_HASH.

  • IPv6 Multicast messages are not supported on VM, while promiscuous mode and allmulticast mode are both set to off. To receive IPv6 Multicast messages on VM, explicitly set the relevant MAC address using rte_eth_dev_mac_addr_add() API.

  • To support a mixed traffic pattern (some buffers from local host memory, some buffers from other devices) with high bandwidth, a mbuf flag is used.

    An application hints the PMD whether or not it should try to inline the given mbuf data buffer. PMD should do the best effort to act upon this request.

    The hint flag RTE_PMD_MLX5_FINE_GRANULARITY_INLINE is dynamic, registered by application with rte_mbuf_dynflag_register(). This flag is purely driver-specific and declared in PMD specific header rte_pmd_mlx5.h, which is intended to be used by the application.

    To query the supported specific flags in runtime, the function rte_pmd_mlx5_get_dyn_flag_names returns the array of currently (over present hardware and configuration) supported specific flags. The “not inline hint” feature operating flow is the following one:

    • application starts
    • probe the devices, ports are created
    • query the port capabilities
    • if port supporting the feature is found
    • register dynamic flag RTE_PMD_MLX5_FINE_GRANULARITY_INLINE
    • application starts the ports
    • on dev_start() PMD checks whether the feature flag is registered and enables the feature support in datapath
    • application might set the registered flag bit in ol_flags field of mbuf being sent and PMD will handle ones appropriately.

  • The amount of descriptors in Tx queue may be limited by data inline settings. Inline data require the more descriptor building blocks and overall block amount may exceed the hardware supported limits. The application should reduce the requested Tx size or adjust data inline settings with txq_inline_max and txq_inline_mpw devargs keys.

  • To provide the packet send scheduling on mbuf timestamps the tx_pp parameter should be specified. When PMD sees the RTE_MBUF_DYNFLAG_TX_TIMESTAMP_NAME set on the packet being sent it tries to synchronize the time of packet appearing on the wire with the specified packet timestamp. It the specified one is in the past it should be ignored, if one is in the distant future it should be capped with some reasonable value (in range of seconds). These specific cases (“too late” and “distant future”) can be optionally reported via device xstats to assist applications to detect the time-related problems.

    The timestamp upper “too-distant-future” limit at the moment of invoking the Tx burst routine can be estimated as tx_pp option (in nanoseconds) multiplied by 2^23. Please note, for the testpmd txonly mode, the limit is deduced from the expression:

    (n_tx_descriptors / burst_size + 1) * inter_burst_gap

    There is no any packet reordering according timestamps is supposed, neither within packet burst, nor between packets, it is an entirely application responsibility to generate packets and its timestamps in desired order. The timestamps can be put only in the first packet in the burst providing the entire burst scheduling.

  • E-Switch decapsulation Flow:

    • can be applied to PF port only.
    • must specify VF port action (packet redirection from PF to VF).
    • optionally may specify tunnel inner source and destination MAC addresses.

  • E-Switch encapsulation Flow:

    • can be applied to VF ports only.
    • must specify PF port action (packet redirection from VF to PF).

  • E-Switch Manager matching:

    • For BlueField with old FW which doesn’t expose the E-Switch Manager vport ID in the capability, matching E-Switch Manager should be used only in BlueField embedded CPU mode.

  • Raw encapsulation:

    • The input buffer, used as outer header, is not validated.

  • Raw decapsulation:

    • The decapsulation is always done up to the outermost tunnel detected by the HW.
    • The input buffer, providing the removal size, is not validated.
    • The buffer size must match the length of the headers to be removed.

  • Outer UDP checksum calculation for encapsulation flow actions:

    • Currently available NVIDIA NICs and DPUs do not have a capability to calculate the UDP checksum in the header added using encapsulation flow actions.

      Applications are required to use 0 in UDP checksum field in such flow actions. Resulting packet will have outer UDP checksum equal to 0.

  • ICMP(code/type/identifier/sequence number) / ICMP6(code/type/identifier/sequence number) matching, IP-in-IP and MPLS flow matching are all mutually exclusive features which cannot be supported together (see Firmware Configuration).

  • LRO:

    • Requires DevX and DV flow to be enabled.

    • KEEP_CRC offload cannot be supported with LRO.

    • The first mbuf length, without head-room, must be big enough to include the TCP header (122B).

    • Rx queue with LRO offload enabled, receiving a non-LRO packet, can forward it with size limited to max LRO size, not to max RX packet length.

    • The driver rounds down the port configuration value max_lro_pkt_size (from rte_eth_rxmode) to a multiple of 256 due to hardware limitation.

    • LRO can be used with outer header of TCP packets of the standard format:

      eth (with or without vlan) / ipv4 or ipv6 / tcp / payload

      Other TCP packets (e.g. with MPLS label) received on Rx queue with LRO enabled, will be received with bad checksum.

    • LRO packet aggregation is performed by HW only for packet size larger than lro_min_mss_size. This value is reported on device start, when debug mode is enabled.

  • CRC:

    • RTE_ETH_RX_OFFLOAD_KEEP_CRC cannot be supported with decapsulation for some NICs (such as ConnectX-6 Dx, ConnectX-6 Lx, ConnectX-7, BlueField-2, and BlueField-3). The capability bit scatter_fcs_w_decap_disable shows NIC support.

  • TX mbuf fast free:

    • fast free offload assumes the all mbufs being sent are originated from the same memory pool and there is no any extra references to the mbufs (the reference counter for each mbuf is equal 1 on tx_burst call). The latter means there should be no any externally attached buffers in mbufs. It is an application responsibility to provide the correct mbufs if the fast free offload is engaged. The mlx5 PMD implicitly produces the mbufs with externally attached buffers if MPRQ option is enabled, hence, the fast free offload is neither supported nor advertised if there is MPRQ enabled.

  • Sample flow:

    • Supports RTE_FLOW_ACTION_TYPE_SAMPLE action only within NIC Rx and E-Switch steering domain.
    • For E-Switch Sampling flow with sample ratio > 1, additional actions are not supported in the sample actions list.
    • For ConnectX-5, the RTE_FLOW_ACTION_TYPE_SAMPLE is typically used as first action in the E-Switch egress flow if with header modify or encapsulation actions.
    • For NIC Rx flow, supports MARK, COUNT, QUEUE, RSS in the sample actions list.
    • For E-Switch mirroring flow, supports RAW ENCAP, Port ID, VXLAN ENCAP, NVGRE ENCAP in the sample actions list.
    • For ConnectX-5 trusted device, the application metadata with SET_TAG index 0 is not supported before RTE_FLOW_ACTION_TYPE_SAMPLE action.

  • Modify Field flow:

    • Supports the ‘set’ and ‘add’ operations for RTE_FLOW_ACTION_TYPE_MODIFY_FIELD action.
    • Modification of an arbitrary place in a packet via the special RTE_FLOW_FIELD_START Field ID is not supported.
    • Modification of the MPLS header is supported only in HWS and only to copy from, the encapsulation level is always 0.
    • Modification of the 802.1Q Tag, VXLAN Network or GENEVE Network ID’s is not supported.
    • Encapsulation levels are not supported, can modify outermost header fields only.
    • Offsets cannot skip past the boundary of a field.
    • If the field type is RTE_FLOW_FIELD_MAC_TYPE and packet contains one or more VLAN headers, the meaningful type field following the last VLAN header is used as modify field operation argument. The modify field action is not intended to modify VLAN headers type field, dedicated VLAN push and pop actions should be used instead.
    • For packet fields (e.g. MAC addresses, IPv4 addresses or L4 ports) offset specifies the number of bits to skip from field’s start, starting from MSB in the first byte, in the network order.
    • For flow metadata fields (e.g. META or TAG) offset specifies the number of bits to skip from field’s start, starting from LSB in the least significant byte, in the host order.

  • Age action:

    • with HW steering (dv_flow_en=2)
      • Using the same indirect count action combined with multiple age actions in different flows may cause a wrong age state for the age actions.
      • Creating/destroying flow rules with indirect age action when it is active (timeout != 0) may cause a wrong age state for the indirect age action.
      • The driver reuses counters for aging action, so for optimization the values in rte_flow_port_attr structure should describe:
        • nb_counters is the number of flow rules using counter (with/without age) in addition to flow rules using only age (without count action).
        • nb_aging_objects is the number of flow rules containing age action.

  • IPv6 header item ‘proto’ field, indicating the next header protocol, should not be set as extension header. In case the next header is an extension header, it should not be specified in IPv6 header item ‘proto’ field. The last extension header item ‘next header’ field can specify the following header protocol type.

  • Match on IPv6 routing extension header supports the following fields only:

    • type
    • next_hdr
    • segments_left

    Only supports HW steering (dv_flow_en=2).

  • Hairpin:

    • Hairpin between two ports could only manual binding and explicit Tx flow mode. For single port hairpin, all the combinations of auto/manual binding and explicit/implicit Tx flow mode could be supported.
    • Hairpin in switchdev SR-IOV mode is not supported till now.

  • Quota:

    • Quota implemented for HWS / template API.
    • Maximal value for quota SET and ADD operations in INT32_MAX (2GB).
    • Application cannot use 2 consecutive ADD updates. Next tokens update after ADD must always be SET.
    • Quota flow action cannot be used with Meter or CT flow actions in the same rule.
    • Quota flow action and item supported in non-root HWS tables.
    • Maximal number of HW quota and HW meter objects <= 16e6.

  • Meter:

    • All the meter colors with drop action will be counted only by the global drop statistics.
    • Yellow detection is only supported with ASO metering.
    • Red color must be with drop action.
    • Meter statistics are supported only for drop case.
    • A meter action created with pre-defined policy must be the last action in the flow except single case where the policy actions are:
      • green: NULL or END.
      • yellow: NULL or END.
      • RED: DROP / END.
    • The only supported meter policy actions:
      • green: QUEUE, RSS, PORT_ID, REPRESENTED_PORT, JUMP, DROP, MODIFY_FIELD, MARK, METER and SET_TAG.
      • yellow: QUEUE, RSS, PORT_ID, REPRESENTED_PORT, JUMP, DROP, MODIFY_FIELD, MARK, METER and SET_TAG.
      • RED: must be DROP.
    • Policy actions of RSS for green and yellow should have the same configuration except queues.
    • Policy with RSS/queue action is not supported when dv_xmeta_en enabled.
    • If green action is METER, yellow action must be the same METER action or NULL.
    • meter profile packet mode is supported.
    • meter profiles of RFC2697, RFC2698 and RFC4115 are supported.
    • RFC4115 implementation is following MEF, meaning yellow traffic may reclaim unused green bandwidth when green token bucket is full.
    • When using DV flow engine (dv_flow_en = 1), if meter has drop count or meter hierarchy contains any meter that uses drop count, it cannot be used by flow rule matching all ports.
    • When using DV flow engine (dv_flow_en = 1), if meter hierarchy contains any meter that has MODIFY_FIELD/SET_TAG, it cannot be used by flow matching all ports.
    • When using HWS flow engine (dv_flow_en = 2), only meter mark action is supported.

  • Integrity:

    • Integrity offload is enabled starting from ConnectX-6 Dx.

    • Verification bits provided by the hardware are l3_ok, ipv4_csum_ok, l4_ok, l4_csum_ok.

    • level value 0 references outer headers.

    • Negative integrity item verification is not supported.

    • Multiple integrity items not supported in a single flow rule.

    • Flow rule items supplied by application must explicitly specify network headers referred by integrity item. For example, if integrity item mask sets l4_ok or l4_csum_ok bits, reference to L4 network header, TCP or UDP, must be in the rule pattern as well:

      flow create 0 ingress pattern integrity level is 0 value mask l3_ok value spec l3_ok / eth / ipv6 / end …

flow create 0 ingress pattern integrity level is 0 value mask l4_ok value spec l4_ok / eth / ipv4 proto is udp / end …

  • Connection tracking:

    • Cannot co-exist with ASO meter, ASO age action in a single flow rule.
    • Flow rules insertion rate and memory consumption need more optimization.
    • 256 ports maximum.
    • 4M connections maximum with dv_flow_en 1 mode. 16M with dv_flow_en 2.

  • Multi-thread flow insertion:

    • In order to achieve best insertion rate, application should manage the flows per lcore.
    • Better to disable memory reclaim by setting reclaim_mem_mode to 0 to accelerate the flow object allocation and release with cache.

  • HW hashed bonding

    • TXQ affinity subjects to HW hash once enabled.

  • Bonding under socket direct mode

    • Needs MLNX_OFED 5.4+.

  • Match on aggregated affinity:

    • Supports NIC ingress flow in group 0.
    • Supports E-Switch flow in group 0 and depends on device-managed flow steering (DMFS) mode.

  • Timestamps:

    • CQE timestamp field width is limited by hardware to 63 bits, MSB is zero.
    • In the free-running mode the timestamp counter is reset on power on and 63-bit value provides over 1800 years of uptime till overflow.
    • In the real-time mode (configurable with REAL_TIME_CLOCK_ENABLE firmware settings), the timestamp presents the nanoseconds elapsed since 01-Jan-1970, hardware timestamp overflow will happen on 19-Jan-2038 (0x80000000 seconds since 01-Jan-1970).
    • The send scheduling is based on timestamps from the reference “Clock Queue” completions, the scheduled send timestamps should not be specified with non-zero MSB.

  • Match on GRE header supports the following fields:

    • c_rsvd0_v: C bit, K bit, S bit
    • protocol type
    • checksum
    • key
    • sequence

    Matching on checksum and sequence needs MLNX_OFED 5.6+.

  • The NIC egress flow rules on representor port are not supported.

  • During live migration to a new process set its flow engine as standby mode, the user should only program flow rules in group 0 (fdb_def_rule_en=0). Live migration is only supported under SWS (dv_flow_en=1). The flow group 0 is shared between DPDK processes while the other flow groups are limited to the current process. The flow engine of a process cannot move from active to standby mode if preceding active application rules are still present and vice versa.

40.5. Statistics

MLX5 supports various methods to report statistics:

Port statistics can be queried using rte_eth_stats_get(). The received and sent statistics are through SW only and counts the number of packets received or sent successfully by the PMD. The imissed counter is the amount of packets that could not be delivered to SW because a queue was full. Packets not received due to congestion in the bus or on the NIC can be queried via the rx_discards_phy xstats counter.

Extended statistics can be queried using rte_eth_xstats_get(). The extended statistics expose a wider set of counters counted by the device. The extended port statistics counts the number of packets received or sent successfully by the port. As NVIDIA NICs are using the Bifurcated Linux Driver those counters counts also packet received or sent by the Linux kernel. The counters with _phy suffix counts the total events on the physical port, therefore not valid for VF.

Finally per-flow statistics can by queried using rte_flow_query when attaching a count action for specific flow. The flow counter counts the number of packets received successfully by the port and match the specific flow.

40.6. Compilation

See mlx5 common compilation.

40.7. Configuration

40.7.1. Environment Configuration

See mlx5 common configuration.

40.7.2. Firmware configuration

See Firmware Configuration guide.

40.7.3. Runtime Configuration

Please refer to mlx5 common options for an additional list of options shared with other mlx5 drivers.

  • rxq_cqe_comp_en parameter [int]

    A nonzero value enables the compression of CQE on RX side. This feature allows to save PCI bandwidth and improve performance. Enabled by default. Different compression formats are supported in order to achieve the best performance for different traffic patterns. Default format depends on Multi-Packet Rx queue configuration: Hash RSS format is used in case MPRQ is disabled, Checksum format is used in case MPRQ is enabled.

    The lower 3 bits define the CQE compression format: Specifying 2 in these bits of the rxq_cqe_comp_en parameter selects the flow tag format for better compression rate in case of flow mark traffic. Specifying 3 in these bits selects checksum format. Specifying 4 in these bits selects L3/L4 header format for better compression rate in case of mixed TCP/UDP and IPv4/IPv6 traffic. CQE compression format selection requires DevX to be enabled. If there is no DevX enabled/supported the value is reset to 1 by default.

    8th bit defines the CQE compression layout. Setting this bit to 1 turns enhanced CQE compression layout on. Enhanced CQE compression is designed for better latency and SW utilization. This bit is ignored if only the basic CQE compression layout is supported.

    Supported on:

    • x86_64 with ConnectX-4, ConnectX-4 Lx, ConnectX-5, ConnectX-6, ConnectX-6 Dx, ConnectX-6 Lx, ConnectX-7, BlueField, BlueField-2, and BlueField-3.
    • POWER9 and ARMv8 with ConnectX-4 Lx, ConnectX-5, ConnectX-6, ConnectX-6 Dx, ConnectX-6 Lx, ConnectX-7 BlueField, BlueField-2, and BlueField-3.

  • rxq_pkt_pad_en parameter [int]

    A nonzero value enables padding Rx packet to the size of cacheline on PCI transaction. This feature would waste PCI bandwidth but could improve performance by avoiding partial cacheline write which may cause costly read-modify-copy in memory transaction on some architectures. Disabled by default.

    Supported on:

    • x86_64 with ConnectX-4, ConnectX-4 Lx, ConnectX-5, ConnectX-6, ConnectX-6 Dx, ConnectX-6 Lx, ConnectX-7, BlueField, BlueField-2, and BlueField-3.
    • POWER8 and ARMv8 with ConnectX-4 Lx, ConnectX-5, ConnectX-6, ConnectX-6 Dx, ConnectX-6 Lx, ConnectX-7, BlueField, BlueField-2, and BlueField-3.

  • delay_drop parameter [int]

    Bitmask value for the Rx queue delay drop attribute. Bit 0 is used for the standard Rx queue and bit 1 is used for the hairpin Rx queue. By default, the delay drop is disabled for all Rx queues. It will be ignored if the port does not support the attribute even if it is enabled explicitly.

    The packets being received will not be dropped immediately when the WQEs are exhausted in a Rx queue with delay drop enabled.

    A timeout value is set in the driver to control the waiting time before dropping a packet. Once the timer is expired, the delay drop will be deactivated for all the Rx queues with this feature enable. To re-activate it, a rearming is needed and it is part of the kernel driver starting from MLNX_OFED 5.5.

    To enable / disable the delay drop rearming, the private flag dropless_rq can be set and queried via ethtool:

    • ethtool –set-priv-flags <netdev> dropless_rq on (/ off)
    • ethtool –show-priv-flags <netdev>

    The configuration flag is global per PF and can only be set on the PF, once it is on, all the VFs’, SFs’ and representors’ Rx queues will share the timer and rearming.

  • mprq_en parameter [int]

    A nonzero value enables configuring Multi-Packet Rx queues. Rx queue is configured as Multi-Packet RQ if the total number of Rx queues is rxqs_min_mprq or more. Disabled by default.

    Multi-Packet Rx Queue (MPRQ a.k.a Striding RQ) can further save PCIe bandwidth by posting a single large buffer for multiple packets. Instead of posting a buffers per a packet, one large buffer is posted in order to receive multiple packets on the buffer. A MPRQ buffer consists of multiple fixed-size strides and each stride receives one packet. MPRQ can improve throughput for small-packet traffic.

    When MPRQ is enabled, MTU can be larger than the size of user-provided mbuf even if RTE_ETH_RX_OFFLOAD_SCATTER isn’t enabled. PMD will configure large stride size enough to accommodate MTU as long as device allows. Note that this can waste system memory compared to enabling Rx scatter and multi-segment packet.

  • mprq_log_stride_num parameter [int]

    Log 2 of the number of strides for Multi-Packet Rx queue. Configuring more strides can reduce PCIe traffic further. If configured value is not in the range of device capability, the default value will be set with a warning message. The default value is 4 which is 16 strides per a buffer, valid only if mprq_en is set.

    The size of Rx queue should be bigger than the number of strides.

  • mprq_log_stride_size parameter [int]

    Log 2 of the size of a stride for Multi-Packet Rx queue. Configuring a smaller stride size can save some memory and reduce probability of a depletion of all available strides due to unreleased packets by an application. If configured value is not in the range of device capability, the default value will be set with a warning message. The default value is 11 which is 2048 bytes per a stride, valid only if mprq_en is set. With mprq_log_stride_size set it is possible for a packet to span across multiple strides. This mode allows support of jumbo frames (9K) with MPRQ. The memcopy of some packets (or part of a packet if Rx scatter is configured) may be required in case there is no space left for a head room at the end of a stride which incurs some performance penalty.

  • mprq_max_memcpy_len parameter [int]

    The maximum length of packet to memcpy in case of Multi-Packet Rx queue. Rx packet is mem-copied to a user-provided mbuf if the size of Rx packet is less than or equal to this parameter. Otherwise, PMD will attach the Rx packet to the mbuf by external buffer attachment - rte_pktmbuf_attach_extbuf(). A mempool for external buffers will be allocated and managed by PMD. If Rx packet is externally attached, ol_flags field of the mbuf will have RTE_MBUF_F_EXTERNAL and this flag must be preserved. RTE_MBUF_HAS_EXTBUF() checks the flag. The default value is 128, valid only if mprq_en is set.

  • rxqs_min_mprq parameter [int]

    Configure Rx queues as Multi-Packet RQ if the total number of Rx queues is greater or equal to this value. The default value is 12, valid only if mprq_en is set.

  • txq_inline parameter [int]

    Amount of data to be inlined during TX operations. This parameter is deprecated and converted to the new parameter txq_inline_max providing partial compatibility.

  • txqs_min_inline parameter [int]

    Enable inline data send only when the number of TX queues is greater or equal to this value.

    This option should be used in combination with txq_inline_max and txq_inline_mpw below and does not affect txq_inline_min settings above.

    If this option is not specified the default value 16 is used for BlueField and 8 for other platforms

    The data inlining consumes the CPU cycles, so this option is intended to auto enable inline data if we have enough Tx queues, which means we have enough CPU cores and PCI bandwidth is getting more critical and CPU is not supposed to be bottleneck anymore.

    The copying data into WQE improves latency and can improve PPS performance when PCI back pressure is detected and may be useful for scenarios involving heavy traffic on many queues.

    Because additional software logic is necessary to handle this mode, this option should be used with care, as it may lower performance when back pressure is not expected.

    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-4 Lx, 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-4 Lx NIC, it is allowed to specify values below 18, but it is not recommended and may prevent NIC from sending packets over some configurations.

    For ConnectX-4 and ConnectX-4 Lx NICs, automatically configured value is insufficient for some traffic, because they require at least all L2 headers to be inlined. For example, Q-in-Q adds 4 bytes to default 18 bytes of Ethernet and VLAN, thus txq_inline_min must be set to 22. MPLS would add 4 bytes per label. Final value must account for all possible L2 encapsulation headers used in particular environment.

    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.

  • txq_mpw_hdr_dseg_en parameter [int]

    A nonzero value enables including two pointers in the first block of TX descriptor. The parameter is deprecated and ignored, kept for compatibility issue.

  • txq_max_inline_len parameter [int]

    Maximum size of packet to be inlined. This limits the size of packet to be inlined. If the size of a packet is larger than configured value, the packet isn’t inlined even though there’s enough space remained in the descriptor. Instead, the packet is included with pointer. This parameter is deprecated and converted directly to txq_inline_mpw providing full compatibility. Valid only if eMPW feature is engaged.

  • txq_mpw_en parameter [int]

    A nonzero value enables Enhanced Multi-Packet Write (eMPW) for ConnectX-5, ConnectX-6, ConnectX-6 Dx, ConnectX-6 Lx, ConnectX-7, BlueField, BlueField-2 BlueField-3. eMPW 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_mpw is set along with txq_mpw_en, Tx burst function copies entire packet data on to Tx descriptor instead of including pointer of packet.

    The Enhanced Multi-Packet Write feature is enabled by default if NIC supports it, can be disabled by explicit specifying 0 value for txq_mpw_en option. Also, if minimal data inlining is requested by non-zero txq_inline_min option or reported by the NIC, the eMPW feature is disengaged.

  • tx_db_nc parameter [int]

    This parameter name is deprecated and ignored. The new name for this parameter is sq_db_nc. See common driver options.

  • tx_pp parameter [int]

    If a nonzero value is specified the driver creates all necessary internal objects to provide accurate packet send scheduling on mbuf timestamps. The positive value specifies the scheduling granularity in nanoseconds, the packet send will be accurate up to specified digits. The allowed range is from 500 to 1 million of nanoseconds. The negative value specifies the module of granularity and engages the special test mode the check the schedule rate. By default (if the tx_pp is not specified) send scheduling on timestamps feature is disabled.

    Starting with ConnectX-7 the capability to schedule traffic directly on timestamp specified in descriptor is provided, no extra objects are needed anymore and scheduling capability is advertised and handled regardless tx_pp parameter presence.

  • tx_skew parameter [int]

    The parameter adjusts the send packet scheduling on timestamps and represents the average delay between beginning of the transmitting descriptor processing by the hardware and appearance of actual packet data on the wire. The value should be provided in nanoseconds and is valid only if tx_pp parameter is specified. The default value is zero.

  • tx_vec_en parameter [int]

    A nonzero value enables Tx vector on ConnectX-5, ConnectX-6, ConnectX-6 Dx, ConnectX-6 Lx, ConnectX-7, BlueField, BlueField-2, and BlueField-3 NICs if the number of global Tx queues on the port is less than txqs_max_vec. The parameter is deprecated and ignored.

  • rx_vec_en parameter [int]

    A nonzero value enables Rx vector if the port is not configured in multi-segment otherwise this parameter is ignored.

    Enabled by default.

  • vf_nl_en parameter [int]

    A nonzero value enables Netlink requests from the VF to add/remove MAC addresses or/and enable/disable promiscuous/all multicast on the Netdevice. Otherwise the relevant configuration must be run with Linux iproute2 tools. This is a prerequisite to receive this kind of traffic.

    Enabled by default, valid only on VF devices ignored otherwise.

  • l3_vxlan_en parameter [int]

    A nonzero value allows L3 VXLAN and VXLAN-GPE flow creation. To enable L3 VXLAN or VXLAN-GPE, users has to configure firmware and enable this parameter. This is a prerequisite to receive this kind of traffic.

    Disabled by default.

  • dv_xmeta_en parameter [int]

    A nonzero value enables extensive flow metadata support if device is capable and driver supports it. This can enable extensive support of MARK and META item of rte_flow. The newly introduced SET_TAG and SET_META actions do not depend on dv_xmeta_en.

    There are some possible configurations, depending on parameter value:

    • 0, this is default value, defines the legacy mode, the MARK and META related actions and items operate only within NIC Tx and NIC Rx steering domains, no MARK and META information crosses the domain boundaries. The MARK item is 24 bits wide, the META item is 32 bits wide and match supported on egress only.
    • 1, this engages extensive metadata mode, the MARK and META related actions and items operate within all supported steering domains, including FDB, MARK and META information may cross the domain boundaries. The MARK item is 24 bits wide, the META item width depends on kernel and firmware configurations and might be 0, 16 or 32 bits. Within NIC Tx domain META data width is 32 bits for compatibility, the actual width of data transferred to the FDB domain depends on kernel configuration and may be vary. The actual supported width can be retrieved in runtime by series of rte_flow_validate() trials.
    • 2, this engages extensive metadata mode, the MARK and META related actions and items operate within all supported steering domains, including FDB, MARK and META information may cross the domain boundaries. The META item is 32 bits wide, the MARK item width depends on kernel and firmware configurations and might be 0, 16 or 24 bits. The actual supported width can be retrieved in runtime by series of rte_flow_validate() trials.
    • 3, this engages tunnel offload mode. In E-Switch configuration, that mode implicitly activates dv_xmeta_en=1.
    • 4, this mode is only supported in HWS (dv_flow_en=2). The Rx/Tx metadata with 32b width copy between FDB and NIC is supported. The mark is only supported in NIC and there is no copy supported.
    Mode MARK META META Tx FDB/Through
    0 24 bits 32 bits 32 bits no
    1 24 bits vary 0-32 32 bits yes
    2 vary 0-24 32 bits 32 bits yes

    If there is no E-Switch configuration the dv_xmeta_en parameter is ignored and the device is configured to operate in legacy mode (0).

    Disabled by default (set to 0).

    The Direct Verbs/Rules (engaged with dv_flow_en = 1) supports all of the extensive metadata features. The legacy Verbs supports FLAG and MARK metadata actions over NIC Rx steering domain only.

    Setting META value to zero in flow action means there is no item provided and receiving datapath will not report in mbufs the metadata are present. Setting MARK value to zero in flow action means the zero FDIR ID value will be reported on packet receiving.

    For the MARK action the last 16 values in the full range are reserved for internal PMD purposes (to emulate FLAG action). The valid range for the MARK action values is 0-0xFFEF for the 16-bit mode and 0-0xFFFFEF for the 24-bit mode, the flows with the MARK action value outside the specified range will be rejected.

  • dv_flow_en parameter [int]

    Value 0 means legacy Verbs flow offloading.

    Value 1 enables the DV flow steering assuming it is supported by the driver (requires rdma-core 24 or higher).

    Value 2 enables the WQE based hardware steering. In this mode, only queue-based flow management is supported.

    It is configured by default to 1 (DV flow steering) if supported. Otherwise, the value is 0 which indicates legacy Verbs flow offloading.

  • dv_esw_en parameter [int]

    A nonzero value enables E-Switch using Direct Rules.

    Enabled by default if supported.

  • fdb_def_rule_en parameter [int]

    A non-zero value enables to create a dedicated rule on E-Switch root table. This dedicated rule forwards all incoming packets into table 1. Other rules will be created in E-Switch table original table level plus one, to improve the flow insertion rate due to skipping root table managed by firmware. If set to 0, all rules will be created on the original E-Switch table level.

    By default, the PMD will set this value to 1.

  • lacp_by_user parameter [int]

    A nonzero value enables the control of LACP traffic by the user application. When a bond exists in the driver, by default it should be managed by the kernel and therefore LACP traffic should be steered to the kernel. If this devarg is set to 1 it will allow the user to manage the bond by itself and not steer LACP traffic to the kernel.

    Disabled by default (set to 0).

  • representor parameter [list]

    This parameter can be used to instantiate DPDK Ethernet devices from existing port (PF, VF or SF) representors configured on the device.

    It is a standard parameter whose format is described in Ethernet Device Standard Device Arguments.

    For instance, to probe VF port representors 0 through 2:

    <PCI_BDF>,representor=vf[0-2]

    To probe SF port representors 0 through 2:

    <PCI_BDF>,representor=sf[0-2]

    To probe VF port representors 0 through 2 on both PFs of bonding device:

    <Primary_PCI_BDF>,representor=pf[0,1]vf[0-2]

  • repr_matching_en parameter [int]

    • 0. If representor matching is disabled, then there will be no implicit item added. As a result, ingress flow rules will match traffic coming to any port, not only the port on which flow rule is created. Because of that, default flow rules for ingress traffic cannot be created and port starts in isolated mode by default. Port cannot be switched back to non-isolated mode.
    • 1. If representor matching is enabled (default setting), then each ingress pattern template has an implicit REPRESENTED_PORT item added. Flow rules based on this pattern template will match the vport associated with port on which rule is created.

  • max_dump_files_num parameter [int]

    The maximum number of files per PMD entity that may be created for debug information. The files will be created in /var/log directory or in current directory.

    set to 128 by default.

  • lro_timeout_usec parameter [int]

    The maximum allowed duration of an LRO session, in micro-seconds. PMD will set the nearest value supported by HW, which is not bigger than the input lro_timeout_usec value. If this parameter is not specified, by default PMD will set the smallest value supported by HW.

  • hp_buf_log_sz parameter [int]

    The total data buffer size of a hairpin queue (logarithmic form), in bytes. PMD will set the data buffer size to 2 ** hp_buf_log_sz, both for RX & TX. The capacity of the value is specified by the firmware and the initialization will get a failure if it is out of scope. The range of the value is from 11 to 19 right now, and the supported frame size of a single packet for hairpin is from 512B to 128KB. It might change if different firmware release is being used. By using a small value, it could reduce memory consumption but not work with a large frame. If the value is too large, the memory consumption will be high and some potential performance degradation will be introduced. By default, the PMD will set this value to 16, which means that 9KB jumbo frames will be supported.

  • reclaim_mem_mode parameter [int]

    Cache some resources in flow destroy will help flow recreation more efficient. While some systems may require the all the resources can be reclaimed after flow destroyed. The parameter reclaim_mem_mode provides the option for user to configure if the resource cache is needed or not.

    There are three options to choose:

    • 0. It means the flow resources will be cached as usual. The resources will be cached, helpful with flow insertion rate.
      1. It will only enable the DPDK PMD level resources reclaim.
    • 2. Both DPDK PMD level and rdma-core low level will be configured as reclaimed mode.

    By default, the PMD will set this value to 0.

  • decap_en parameter [int]

    Some devices do not support FCS (frame checksum) scattering for tunnel-decapsulated packets. If set to 0, this option forces the FCS feature and rejects tunnel decapsulation in the flow engine for such devices.

    By default, the PMD will set this value to 1.

  • allow_duplicate_pattern parameter [int]

    There are two options to choose:

    • 0. Prevent insertion of rules with the same pattern items on non-root table. In this case, only the first rule is inserted and the following rules are rejected and error code EEXIST is returned.
    • 1. Allow insertion of rules with the same pattern items. In this case, all rules are inserted but only the first rule takes effect, the next rule takes effect only if the previous rules are deleted.

    By default, the PMD will set this value to 1.

40.8. Sub-Function

See Sub-Function with MLNX_OFED/EN.

40.8.1. Sub-Function representor support

A SF netdev supports E-Switch representation offload similar to PF and VF representors. Use <sfnum> to probe SF representor:

testpmd> port attach <PCI_BDF>,representor=sf<sfnum>,dv_flow_en=1

40.9. Performance tuning

  1. Configure aggressive CQE Zipping for maximum performance:

    mlxconfig -d <mst device> s CQE_COMPRESSION=1

To set it back to the default CQE Zipping mode use:

mlxconfig -d <mst device> s CQE_COMPRESSION=0

  1. In case of virtualization:

    • Make sure that hypervisor kernel is 3.16 or newer.
    • Configure boot with iommu=pt.
    • Use 1G huge pages.
    • Make sure to allocate a VM on huge pages.
    • Make sure to set CPU pinning.

  2. Use the CPU near local NUMA node to which the PCIe adapter is connected, for better performance. For VMs, verify that the right CPU and NUMA node are pinned according to the above. Run:

    lstopo-no-graphics --merge

    to identify the NUMA node to which the PCIe adapter is connected.

  3. If more than one adapter is used, and root complex capabilities allow to put both adapters on the same NUMA node without PCI bandwidth degradation, it is recommended to locate both adapters on the same NUMA node. This in order to forward packets from one to the other without NUMA performance penalty.

  4. Disable pause frames:

    ethtool -A <netdev> rx off tx off

  5. Verify IO non-posted prefetch is disabled by default. This can be checked via the BIOS configuration. Please contact you server provider for more information about the settings.

Note

On some machines, depends on the machine integrator, it is beneficial to set the PCI max read request parameter to 1K. This can be done in the following way:

To query the read request size use:

setpci -s <NIC PCI address> 68.w

If the output is different than 3XXX, set it by:

setpci -s <NIC PCI address> 68.w=3XXX

The XXX can be different on different systems. Make sure to configure according to the setpci output.

  1. To minimize overhead of searching Memory Regions:
    • ‘–socket-mem’ is recommended to pin memory by predictable amount.
    • Configure per-lcore cache when creating Mempools for packet buffer.
    • Refrain from dynamically allocating/freeing memory in run-time.

40.10. Rx burst functions

There are multiple Rx burst functions with different advantages and limitations.

Table 40.1 Rx burst functions
Function Name
Enabler
Scatter
Error Recovery
CQE
comp
Large
MTU
rx_burst rx_vec_en=0 Yes Yes Yes Yes
rx_burst_vec rx_vec_en=1 (default) No if CQE comp off Yes No
rx_burst_mprq
mprq_en=1
RxQs >= rxqs_min_mprq
 No Yes Yes Yes
rx_burst_mprq_vec
rx_vec_en=1 (default)
mprq_en=1
RxQs >= rxqs_min_mprq
 No if CQE comp off Yes Yes

40.11. Supported hardware offloads

Below tables show offload support depending on hardware, firmware, and Linux software support.

The Linux prerequisites are Linux kernel and rdma-core libraries. These dependencies are also packaged in MLNX_OFED or MLNX_EN, shortened below as “OFED”.

Table 40.2 Minimal SW/HW versions for queue offloads
Offload DPDK Linux rdma-core OFED firmware hardware
common base 17.11 4.14 16 4.2-1 12.21.1000 ConnectX-4
checksums 17.11 4.14 16 4.2-1 12.21.1000 ConnectX-4
Rx timestamp 17.11 4.14 16 4.2-1 12.21.1000 ConnectX-4
TSO 17.11 4.14 16 4.2-1 12.21.1000 ConnectX-4
LRO 19.08 N/A N/A 4.6-4 16.25.6406 ConnectX-5
Tx scheduling 20.08 N/A N/A 5.1-2 22.28.2006 ConnectX-6 Dx
Buffer Split 20.11 N/A N/A 5.1-2 16.28.2006 ConnectX-5
Table 40.3 Minimal SW/HW versions for rte_flow offloads
Offload with E-Switch with NIC
Count
DPDK 19.05
OFED 4.6
rdma-core 24
ConnectX-5
DPDK 19.02
OFED 4.6
rdma-core 23
ConnectX-5
Drop
DPDK 19.05
OFED 4.6
rdma-core 24
ConnectX-5
DPDK 18.11
OFED 4.5
rdma-core 23
ConnectX-4
Queue / RSS

N/A
DPDK 18.11
OFED 4.5
rdma-core 23
ConnectX-4
Shared action

Table 40.4

Table 40.4
VLAN
(of_pop_vlan /
of_push_vlan /
of_set_vlan_pcp /
of_set_vlan_vid)
DPDK 19.11
OFED 4.7-1
ConnectX-5
DPDK 19.11
OFED 4.7-1
ConnectX-5
VLAN
ingress and /
of_push_vlan /
DPDK 21.05
OFED 5.3
ConnectX-6 Dx

N/A
VLAN
egress and /
of_pop_vlan /
DPDK 21.05
OFED 5.3
ConnectX-6 Dx

N/A
Encapsulation (VXLAN / NVGRE / RAW)
DPDK 19.05
OFED 4.7-1
rdma-core 24
ConnectX-5
DPDK 19.02
OFED 4.6
rdma-core 23
ConnectX-5
Encapsulation GENEVE
DPDK 19.11
OFED 4.7-3
rdma-core 27
ConnectX-5
DPDK 19.11
OFED 4.7-3
rdma-core 27
ConnectX-5
Tunnel Offload
DPDK 20.11
OFED 5.1-2
rdma-core 32
ConnectX-5
DPDK 20.11
OFED 5.1-2
N/A
ConnectX-5
Header rewrite
(set_ipv4_src /
set_ipv4_dst /
set_ipv6_src /
set_ipv6_dst /
set_tp_src /
set_tp_dst /
dec_ttl /
set_ttl /
set_mac_src /
set_mac_dst)
DPDK 19.05
OFED 4.7-1
rdma-core 24
ConnectX-5
DPDK 19.02
OFED 4.7-1
rdma-core 24
ConnectX-5
Header rewrite
(set_dscp)
DPDK 20.02
OFED 5.0
rdma-core 24
ConnectX-5
DPDK 20.02
OFED 5.0
rdma-core 24
ConnectX-5
Header rewrite
(ipv4_ecn /
ipv6_ecn)
DPDK 22.07
OFED 5.6-2
rdma-core 41
ConnectX-5
DPDK 22.07
OFED 5.6-2
rdma-core 41
ConnectX-5
Jump
DPDK 19.05
OFED 4.7-1
rdma-core 24
ConnectX-5
DPDK 19.02
OFED 4.7-1
N/A
ConnectX-5
Mark / Flag
DPDK 19.05
OFED 4.6
rdma-core 24
ConnectX-5
DPDK 18.11
OFED 4.5
rdma-core 23
ConnectX-4
Meta data
DPDK 19.11
OFED 4.7-3
rdma-core 26
ConnectX-5
DPDK 19.11
OFED 4.7-3
rdma-core 26
ConnectX-5
Port ID
DPDK 19.05
OFED 4.7-1
rdma-core 24
ConnectX-5
N/A
N/A
N/A
N/A
Hairpin

N/A
DPDK 19.11
OFED 4.7-3
rdma-core 26
ConnectX-5
2-port Hairpin

N/A
DPDK 20.11
OFED 5.1-2
N/A
ConnectX-5
Metering
DPDK 19.11
OFED 4.7-3
rdma-core 26
ConnectX-5
DPDK 19.11
OFED 4.7-3
rdma-core 26
ConnectX-5
ASO Metering
DPDK 21.05
OFED 5.3
rdma-core 33
ConnectX-6 Dx
DPDK 21.05
OFED 5.3
rdma-core 33
ConnectX-6 Dx
Metering Hierarchy
DPDK 21.08
OFED 5.3
N/A
ConnectX-6 Dx
DPDK 21.08
OFED 5.3
N/A
ConnectX-6 Dx
Sampling
DPDK 20.11
OFED 5.1-2
rdma-core 32
ConnectX-5
DPDK 20.11
OFED 5.1-2
N/A
ConnectX-5
Encapsulation GTP PSC
DPDK 21.02
OFED 5.2
rdma-core 35
ConnectX-6 Dx
DPDK 21.02
OFED 5.2
rdma-core 35
ConnectX-6 Dx
Encapsulation GENEVE TLV option
DPDK 21.02
OFED 5.2
rdma-core 34
ConnectX-6 Dx
DPDK 21.02
OFED 5.2
rdma-core 34
ConnectX-6 Dx
Modify Field
DPDK 21.02
OFED 5.2
rdma-core 35
ConnectX-5
DPDK 21.02
OFED 5.2
rdma-core 35
ConnectX-5
Connection tracking

N/A
DPDK 21.05
OFED 5.3
rdma-core 35
ConnectX-6 Dx
Table 40.4 Minimal SW/HW versions for shared action offload
Shared Action with E-Switch with NIC
RSS

N/A
DPDK 20.11
OFED 5.2
rdma-core 33
ConnectX-5
Age
DPDK 20.11
OFED 5.2
rdma-core 32
ConnectX-6 Dx
DPDK 20.11
OFED 5.2
rdma-core 32
ConnectX-6 Dx
Count
DPDK 21.05
OFED 4.6
rdma-core 24
ConnectX-5
DPDK 21.05
OFED 4.6
rdma-core 23
ConnectX-5
Table 40.5 Minimal SW/HW versions for flow template API
DPDK NIC Firmware
22.11 ConnectX-6 Dx xx.35.1012

40.12. Notes for metadata

MARK and META items are interrelated with datapath - they might move from/to the applications in mbuf fields. Hence, zero value for these items has the special meaning - it means “no metadata are provided”, not zero values are treated by applications and PMD as valid ones.

Moreover in the flow engine domain the value zero is acceptable to match and set, and we should allow to specify zero values as rte_flow parameters for the META and MARK items and actions. In the same time zero mask has no meaning and should be rejected on validation stage.

40.13. Notes for rte_flow

Flows are not cached in the driver. When stopping a device port, all the flows created on this port from the application will be flushed automatically in the background. After stopping the device port, all flows on this port become invalid and not represented in the system. All references to these flows held by the application should be discarded directly but neither destroyed nor flushed.

The application should re-create the flows as required after the port restart.

40.14. Notes for hairpin

NVIDIA ConnectX and BlueField devices support specifying memory placement for hairpin Rx and Tx queues. This feature requires NVIDIA MLNX_OFED 5.8.

By default, data buffers and packet descriptors for hairpin queues are placed in device memory which is shared with other resources (e.g. flow rules).

Starting with DPDK 22.11 and NVIDIA MLNX_OFED 5.8, applications are allowed to:

  1. Place data buffers and Rx packet descriptors in dedicated device memory. Application can request that configuration through use_locked_device_memory configuration option.

    Placing data buffers and Rx packet descriptors in dedicated device memory can decrease latency on hairpinned traffic, since traffic processing for the hairpin queue will not be memory starved.

    However, reserving device memory for hairpin Rx queues may decrease throughput under heavy load, since less resources will be available on device.

    This option is supported only for Rx hairpin queues.

  2. Place Tx packet descriptors in host memory. Application can request that configuration through use_rte_memory configuration option.

    Placing Tx packet descritors in host memory can increase traffic throughput. This results in more resources available on the device for other purposes, which reduces memory contention on device. Side effect of this option is visible increase in latency, since each packet incurs additional PCI transactions.

    This option is supported only for Tx hairpin queues.

40.15. Notes for testpmd

Compared to librte_net_mlx4 that implements a single RSS configuration per port, librte_net_mlx5 supports per-protocol RSS configuration.

Since testpmd defaults to IP RSS mode and there is currently no command-line parameter to enable additional protocols (UDP and TCP as well as IP), the following commands must be entered from its CLI to get the same behavior as librte_net_mlx4:

> port stop all
> port config all rss all
> port start all

40.16. Usage example

This section demonstrates how to launch testpmd with NVIDIA ConnectX-4/ConnectX-5/ConnectX-6/BlueField devices managed by librte_net_mlx5.

  1. Load the kernel modules:

    modprobe -a ib_uverbs mlx5_core mlx5_ib

    Alternatively if MLNX_OFED/MLNX_EN is fully installed, the following script can be run:

    /etc/init.d/openibd restart

    Note

    User space I/O kernel modules (uio and igb_uio) are not used and do not have to be loaded.

  2. Make sure Ethernet interfaces are in working order and linked to kernel verbs. Related sysfs entries should be present:

    ls -d /sys/class/net/*/device/infiniband_verbs/uverbs* | cut -d / -f 5

    Example output:

    eth30
eth31
eth32
eth33

  3. Optionally, retrieve their PCI bus addresses for to be used with the allow list:

    {
    for intf in eth2 eth3 eth4 eth5;
    do
        (cd "/sys/class/net/${intf}/device/" && pwd -P);
    done;
} |
sed -n 's,.*/\(.*\),-a \1,p'

    Example output:

    -a 0000:05:00.1
-a 0000:06:00.0
-a 0000:06:00.1
-a 0000:05:00.0

  4. Request huge pages:

    dpdk-hugepages.py --setup 2G

  5. Start testpmd with basic parameters:

    dpdk-testpmd -l 8-15 -n 4 -a 05:00.0 -a 05:00.1 -a 06:00.0 -a 06:00.1 -- --rxq=2 --txq=2 -i

    Example output:

    [...]
EAL: PCI device 0000:05:00.0 on NUMA socket 0
EAL:   probe driver: 15b3:1013 librte_net_mlx5
PMD: librte_net_mlx5: PCI information matches, using device "mlx5_0" (VF: false)
PMD: librte_net_mlx5: 1 port(s) detected
PMD: librte_net_mlx5: port 1 MAC address is e4:1d:2d:e7:0c:fe
EAL: PCI device 0000:05:00.1 on NUMA socket 0
EAL:   probe driver: 15b3:1013 librte_net_mlx5
PMD: librte_net_mlx5: PCI information matches, using device "mlx5_1" (VF: false)
PMD: librte_net_mlx5: 1 port(s) detected
PMD: librte_net_mlx5: port 1 MAC address is e4:1d:2d:e7:0c:ff
EAL: PCI device 0000:06:00.0 on NUMA socket 0
EAL:   probe driver: 15b3:1013 librte_net_mlx5
PMD: librte_net_mlx5: PCI information matches, using device "mlx5_2" (VF: false)
PMD: librte_net_mlx5: 1 port(s) detected
PMD: librte_net_mlx5: port 1 MAC address is e4:1d:2d:e7:0c:fa
EAL: PCI device 0000:06:00.1 on NUMA socket 0
EAL:   probe driver: 15b3:1013 librte_net_mlx5
PMD: librte_net_mlx5: PCI information matches, using device "mlx5_3" (VF: false)
PMD: librte_net_mlx5: 1 port(s) detected
PMD: librte_net_mlx5: port 1 MAC address is e4:1d:2d:e7:0c:fb
Interactive-mode selected
Configuring Port 0 (socket 0)
PMD: librte_net_mlx5: 0x8cba80: TX queues number update: 0 -> 2
PMD: librte_net_mlx5: 0x8cba80: RX queues number update: 0 -> 2
Port 0: E4:1D:2D:E7:0C:FE
Configuring Port 1 (socket 0)
PMD: librte_net_mlx5: 0x8ccac8: TX queues number update: 0 -> 2
PMD: librte_net_mlx5: 0x8ccac8: RX queues number update: 0 -> 2
Port 1: E4:1D:2D:E7:0C:FF
Configuring Port 2 (socket 0)
PMD: librte_net_mlx5: 0x8cdb10: TX queues number update: 0 -> 2
PMD: librte_net_mlx5: 0x8cdb10: RX queues number update: 0 -> 2
Port 2: E4:1D:2D:E7:0C:FA
Configuring Port 3 (socket 0)
PMD: librte_net_mlx5: 0x8ceb58: TX queues number update: 0 -> 2
PMD: librte_net_mlx5: 0x8ceb58: RX queues number update: 0 -> 2
Port 3: E4:1D:2D:E7:0C:FB
Checking link statuses...
Port 0 Link Up - speed 40000 Mbps - full-duplex
Port 1 Link Up - speed 40000 Mbps - full-duplex
Port 2 Link Up - speed 10000 Mbps - full-duplex
Port 3 Link Up - speed 10000 Mbps - full-duplex
Done
testpmd>

40.17. How to dump flows

This section demonstrates how to dump flows. Currently, it’s possible to dump all flows with assistance of external tools.

  1. 2 ways to get flow raw file:

    • Using testpmd CLI:
    To dump all flows:
testpmd> flow dump <port> all <output_file>
and dump one flow:
testpmd> flow dump <port> rule <rule_id> <output_file>
    • call rte_flow_dev_dump api:
    rte_flow_dev_dump(port, flow, file, NULL);

  2. Dump human-readable flows from raw file:

    Get flow parsing tool from: https://github.com/Mellanox/mlx_steering_dump

    mlx_steering_dump.py -f <output_file> -flowptr <flow_ptr>

40.18. How to share a meter between ports in the same switch domain

This section demonstrates how to use the shared meter. A meter M can be created on port X and to be shared with a port Y on the same switch domain by the next way:

flow create X ingress transfer pattern eth / port_id id is Y / end actions meter mtr_id M / end

40.19. How to use meter hierarchy

This section demonstrates how to create and use a meter hierarchy. A termination meter M can be the policy green action of another termination meter N. The two meters are chained together as a chain. Using meter N in a flow will apply both the meters in hierarchy on that flow.

add port meter policy 0 1 g_actions queue index 0 / end y_actions end r_actions drop / end
create port meter 0 M 1 1 yes 0xffff 1 0
add port meter policy 0 2 g_actions meter mtr_id M / end y_actions end r_actions drop / end
create port meter 0 N 2 2 yes 0xffff 1 0
flow create 0 ingress group 1 pattern eth / end actions meter mtr_id N / end

40.20. How to configure a VF as trusted

This section demonstrates how to configure a virtual function (VF) interface as trusted. Trusted VF is needed to offload rules with rte_flow to a group that is bigger than 0. The configuration is done in two parts: driver and FW.

The procedure below is an example of using a ConnectX-5 adapter card (pf0) with 2 VFs:

  1. Create 2 VFs on the PF pf0 when in Legacy SR-IOV mode:

    $ echo 2 > /sys/class/net/pf0/device/mlx5_num_vfs

  2. Verify the VFs are created:

    $ lspci | grep Mellanox
82:00.0 Ethernet controller: Mellanox Technologies MT27800 Family [ConnectX-5]
82:00.1 Ethernet controller: Mellanox Technologies MT27800 Family [ConnectX-5]
82:00.2 Ethernet controller: Mellanox Technologies MT27800 Family [ConnectX-5 Virtual Function]
82:00.3 Ethernet controller: Mellanox Technologies MT27800 Family [ConnectX-5 Virtual Function]

  3. Unbind all VFs. For each VF PCIe, using the following command to unbind the driver:

    $ echo "0000:82:00.2" >> /sys/bus/pci/drivers/mlx5_core/unbind

  4. Set the VFs to be trusted for the kernel by using one of the methods below:

    • Using sysfs file:

      $ echo ON | tee /sys/class/net/pf0/device/sriov/0/trust
$ echo ON | tee /sys/class/net/pf0/device/sriov/1/trust

    • Using “ip link” command:

      $ ip link set p0 vf 0 trust on
$ ip link set p0 vf 1 trust on

  5. Configure all VFs using mlxreg:

    • For MFT >= 4.21:

      $ mlxreg -d /dev/mst/mt4121_pciconf0 --reg_name VHCA_TRUST_LEVEL --yes --indexes 'all_vhca=0x1,vhca_id=0x0' --set 'trust_level=0x1'

    • For MFT < 4.21:

      $ mlxreg -d /dev/mst/mt4121_pciconf0 --reg_name VHCA_TRUST_LEVEL --yes --set "all_vhca=0x1,trust_level=0x1"

    Note

    Firmware version used must be >= xx.29.1016 and MFT >= 4.18

  6. For each VF PCIe, using the following command to bind the driver:

    $ echo "0000:82:00.2" >> /sys/bus/pci/drivers/mlx5_core/bind

40.21. How to trace Tx datapath

The mlx5 PMD provides Tx datapath tracing capability with extra debug information: when and how packets were scheduled, and when the actual sending was completed by the NIC hardware.

Steps to enable Tx datapath tracing:

  1. Build DPDK application with enabled datapath tracing

    The Meson option --enable_trace_fp=true and the C flag ALLOW_EXPERIMENTAL_API should be specified.

    meson configure --buildtype=debug -Denable_trace_fp=true
   -Dc_args='-DRTE_LIBRTE_MLX5_DEBUG -DRTE_ENABLE_ASSERT -DALLOW_EXPERIMENTAL_API' build

  2. Configure the NIC

    If the sending completion timings are important, the NIC should be configured to provide realtime timestamps. The non-volatile settings parameter REAL_TIME_CLOCK_ENABLE should be configured as 1.

    mlxconfig -d /dev/mst/mt4125_pciconf0 s REAL_TIME_CLOCK_ENABLE=1

    The mlxconfig utility is part of the MFT package.

  3. Run application with EAL parameter enabling tracing in mlx5 Tx datapath

    By default all tracepoints are disabled. To analyze Tx datapath and its timings: --trace=pmd.net.mlx5.tx.

  4. Commit the tracing data to the storage (with rte_trace_save() API call).

  5. Install or build the babeltrace2 package

    The Python script analyzing gathered trace data uses the babeltrace2 library. The package should be either installed or built from source as shown below.

    git clone https://github.com/efficios/babeltrace.git
cd babeltrace
./bootstrap
./configure -help
./configure --disable-api-doc --disable-man-pages
            --disable-python-bindings-doc --enable-python-plugins
            --enable-python-binding

  6. Run analyzing script

    mlx5_trace.py is used to combine related events (packet firing and completion) and to show the results in human-readable view.

    The analyzing script is located in the DPDK source tree: drivers/net/mlx5/tools.

    It requires Python 3.6 and babeltrace2 package.

    The parameter of the script is the trace data folder.

    mlx5_trace.py /var/log/rte-2023-01-23-AM-11-52-39

  7. Interpreting the script output data

    All the timings are given in nanoseconds. The list of Tx bursts per port/queue is presented in the output. Each list element contains the list of built WQEs with specific opcodes. Each WQE contains the list of the encompassed packets to send.

40.22. Host shaper

Host shaper register is per host port register which sets a shaper on the host port. All VF/host PF representors belonging to one host port share one host shaper. For example, if representor 0 and representor 1 belong to the same host port, and a host shaper rate of 1Gbps is configured, the shaper throttles both representors traffic from the host.

Host shaper has two modes for setting the shaper, immediate and deferred to available descriptor threshold event trigger.

In immediate mode, the rate limit is configured immediately to host shaper.

When deferring to the available descriptor threshold trigger, the shaper is not set until an available descriptor threshold event is received by any Rx queue in a VF representor belonging to the host port. The only rate supported for deferred mode is 100Mbps (there is no limit on the supported rates for immediate mode). In deferred mode, the shaper is set on the host port by the firmware upon receiving the available descriptor threshold event, which allows throttling host traffic on available descriptor threshold events at minimum latency, preventing excess drops in the Rx queue.

40.22.1. Dependency on mstflint package

In order to configure host shaper register, librte_net_mlx5 depends on libmtcr_ul which can be installed from MLNX_OFED mstflint package. Meson detects libmtcr_ul existence at configure stage. If the library is detected, the application must link with -lmtcr_ul, as done by the pkg-config file libdpdk.pc.

40.22.2. Available descriptor threshold and host shaper

There is a command to configure the available descriptor threshold in testpmd. Testpmd also contains sample logic to handle available descriptor threshold events. The typical workflow is: testpmd configures available descriptor threshold for Rx queues, enables avail_thresh_triggered in host shaper and registers a callback. When traffic from the host is too high and Rx queue emptiness is below the available descriptor threshold, the PMD receives an event and the firmware configures a 100Mbps shaper on the host port automatically. Then the PMD call the callback registered previously, which will delay a while to let Rx queue empty, then disable host shaper.

Let’s assume we have a simple BlueField-2 setup: port 0 is uplink, port 1 is VF representor. Each port has 2 Rx queues. To control traffic from the host to the Arm device, we can enable the available descriptor threshold in testpmd by:

testpmd> mlx5 set port 1 host_shaper avail_thresh_triggered 1 rate 0
testpmd> set port 1 rxq 0 avail_thresh 70
testpmd> set port 1 rxq 1 avail_thresh 70

The first command disables the current host shaper and enables the available descriptor threshold triggered mode. The other commands configure the available descriptor threshold to 70% of Rx queue size for both Rx queues.

When traffic from the host is too high, testpmd console prints log about available descriptor threshold event, then host shaper is disabled. The traffic rate from the host is controlled and less drop happens in Rx queues.

The threshold event and shaper can be disabled like this:

testpmd> mlx5 set port 1 host_shaper avail_thresh_triggered 0 rate 0
testpmd> set port 1 rxq 0 avail_thresh 0
testpmd> set port 1 rxq 1 avail_thresh 0

It is recommended an application disables the available descriptor threshold and avail_thresh_triggered before exit, if it enables them before.

The shaper can also be configured with a value, the rate unit is 100Mbps. Below, the command sets the current shaper to 5Gbps and disables avail_thresh_triggered.

testpmd> mlx5 set port 1 host_shaper avail_thresh_triggered 0 rate 50

40.23. Testpmd driver specific commands

40.23.1. port attach with socket path

It is possible to allocate a port with libibverbs from external application. For importing the external port with extra device arguments, there is a specific testpmd command similar to port attach command:

testpmd> mlx5 port attach (identifier) socket=(path)

where:

  • identifier: device identifier with optional parameters as same as port attach command.
  • path: path to IPC server socket created by the external application.

This command performs:

  1. Open IPC client socket using the given path, and connect it.
  2. Import ibverbs context and ibverbs protection domain.
  3. Add two device arguments for context (cmd_fd) and protection domain (pd_handle) to the device identifier. See mlx5 driver options for more information about these device arguments.
  4. Call the regular port attach function with updated identifier.

For example, to attach a port whose PCI address is 0000:0a:00.0 and its socket path is /var/run/import_ipc_socket:

testpmd> mlx5 port attach 0000:0a:00.0 socket=/var/run/import_ipc_socket
testpmd: MLX5 socket path is /var/run/import_ipc_socket
testpmd: Attach port with extra devargs 0000:0a:00.0,cmd_fd=40,pd_handle=1
Attaching a new port...
EAL: Probe PCI driver: mlx5_pci (15b3:101d) device: 0000:0a:00.0 (socket 0)
Port 0 is attached. Now total ports is 1
Done

40.23.2. port map external Rx queue

External Rx queue indexes mapping management.

Map HW queue index (32-bit) to ethdev queue index (16-bit) for external Rx queue:

testpmd> mlx5 port (port_id) ext_rxq map (sw_queue_id) (hw_queue_id)

Unmap external Rx queue:

testpmd> mlx5 port (port_id) ext_rxq unmap (sw_queue_id)

where:

  • sw_queue_id: queue index in range [64536, 65535]. This range is the highest 1000 numbers.
  • hw_queue_id: queue index given by HW in queue creation.