35. MLX5 poll mode driver

The MLX5 poll mode driver library (librte_net_mlx5) provides support for Mellanox ConnectX-4, Mellanox ConnectX-4 Lx , Mellanox ConnectX-5, Mellanox ConnectX-6, Mellanox ConnectX-6 Dx, Mellanox ConnectX-6 Lx, Mellanox BlueField and Mellanox BlueField-2 families of 10/25/40/50/100/200 Gb/s adapters as well as their virtual functions (VF) in SR-IOV context.

Information and documentation about these adapters can be found on the Mellanox website. Help is also provided by the Mellanox community.

There is also a section dedicated to this poll mode driver.

35.1. 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.

For security reasons and robustness, this driver only deals with virtual memory addresses. The way resources allocations are handled by the kernel, combined with hardware specifications that allow to handle virtual memory addresses directly, ensure that DPDK applications cannot access random physical memory (or memory that does not belong to the current process).

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.

The PMD can use libibverbs and libmlx5 to access the device firmware or directly the hardware components. There are different levels of objects and bypassing abilities to get the best performances:

  • Verbs is a complete high-level generic API
  • Direct Verbs is a device-specific API
  • DevX allows to access firmware objects
  • Direct Rules manages flow steering at low-level hardware layer

Enabling librte_net_mlx5 causes DPDK applications to be linked against libibverbs.

35.2. Features

  • Multi arch support: x86_64, POWER8, ARMv8, i686.
  • Multiple TX and RX queues.
  • 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.
  • 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.
  • 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.

35.3. Limitations

  • For secondary process:

    • Forked secondary process not supported.
    • 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.

  • 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.

  • VLAN push offload is not supported on ingress traffic.

  • 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.

  • Flows with a VXLAN Network Identifier equal (or ends to be equal) to 0 are not supported.

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

  • Match on Geneve header supports the following fields only:

    • VNI
    • OAM
    • protocol type
    • options length Currently, the only supported options length value is 0.

  • 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

  • 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 EXT_ATTACHED_MBUF 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.

  • 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 PKT_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).

  • 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.

  • ICMP(code/type/identifier/sequence number) / ICMP6(code/type) 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:

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

  • Sample flow:

    • Supports RTE_FLOW_ACTION_TYPE_SAMPLE action only within NIC Rx and E-Switch steering domain.
    • The E-Switch Sample flow must have the eswitch_manager VPORT destination (PF or ECPF) and no additional actions.
    • 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 ConnectX-5 trusted device, the application metadata with SET_TAG index 0 is not supported before RTE_FLOW_ACTION_TYPE_SAMPLE 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.

  • 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.

  • 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.

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

35.4. 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 Mellanox 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.

35.5. Configuration

35.5.1. Compilation options

The ibverbs libraries can be linked with this PMD in a number of ways, configured by the ibverbs_link build option:

  • shared (default): the PMD depends on some .so files.
  • dlopen: Split the dependencies glue in a separate library loaded when needed by dlopen. It make dependencies on libibverbs and libmlx4 optional, and has no performance impact.
  • static: Embed static flavor of the dependencies libibverbs and libmlx4 in the PMD shared library or the executable static binary.

35.5.2. Environment variables

  • MLX5_GLUE_PATH

    A list of directories in which to search for the rdma-core “glue” plug-in, separated by colons or semi-colons.

  • MLX5_SHUT_UP_BF

    Configures HW Tx doorbell register as IO-mapped.

    By default, the HW Tx doorbell is configured as a write-combining register. The register would be flushed to HW usually when the write-combining buffer becomes full, but it depends on CPU design.

35.5.3. Run-time configuration

  • librte_net_mlx5 brings kernel network interfaces up during initialization because it is affected by their state. Forcing them down prevents packets reception.
  • ethtool operations on related kernel interfaces also affect the PMD.

35.5.3.1. Run as non-root

In order to run as a non-root user, some capabilities must be granted to the application:

setcap cap_sys_admin,cap_net_admin,cap_net_raw,cap_ipc_lock+ep <dpdk-app>

Below are the reasons of the need for each capability:

cap_sys_admin
When using physical addresses (PA mode), with Linux >= 4.0, for access to /proc/self/pagemap.
cap_net_admin
For device configuration.
cap_net_raw
For raw ethernet queue allocation through kernel driver.
cap_ipc_lock
For DMA memory pinning.

35.5.3.2. Driver options

  • 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.

    Specifying 2 as a rxq_cqe_comp_en value selects Flow Tag format for better compression rate in case of RTE Flow Mark traffic. Specifying 3 as a rxq_cqe_comp_en value selects Checksum format. Specifying 4 as a rxq_cqe_comp_en value 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.

    Supported on:

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

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

  • 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, max_rx_pkt_len can be larger than the size of user-provided mbuf even if DEV_RX_OFFLOAD_SCATTER isn’t enabled. PMD will configure large stride size enough to accommodate max_rx_pkt_len 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 EXT_ATTACHED_MBUF 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, BlueField, BlueField-2. 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]

    The rdma core library can map doorbell register in two ways, depending on the environment variable “MLX5_SHUT_UP_BF”:

    • As regular cached memory (usually with write combining attribute), if the variable is either missing or set to zero.
    • As non-cached memory, if the variable is present and set to not “0” value.

    The type of mapping may slightly affect the Tx performance, the optimal choice is strongly relied on the host architecture and should be deduced practically.

    If tx_db_nc is set to zero, the doorbell is forced to be mapped to regular memory (with write combining), the PMD will perform the extra write memory barrier after writing to doorbell, it might increase the needed CPU clocks per packet to send, but latency might be improved.

    If tx_db_nc is set to one, the doorbell is forced to be mapped to non cached memory, the PMD will not perform the extra write memory barrier after writing to doorbell, on some architectures it might improve the performance.

    If tx_db_nc is set to two, the doorbell is forced to be mapped to regular memory, the PMD will use heuristics to decide whether write memory barrier should be performed. For bursts with size multiple of recommended one (64 pkts) it is supposed the next burst is coming and no need to issue the extra memory barrier (it is supposed to be issued in the next coming burst, at least after descriptor writing). It might increase latency (on some hosts till next packets transmit) and should be used with care.

    If tx_db_nc is omitted or set to zero, the preset (if any) environment variable “MLX5_SHUT_UP_BF” value is used. If there is no “MLX5_SHUT_UP_BF”, the default tx_db_nc value is zero for ARM64 hosts and one for others.

  • 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.

  • 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, BlueField and BlueField-2 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.
    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]

    A nonzero value enables the DV flow steering assuming it is supported by the driver (RDMA Core library version is rdma-core-24.0 or higher).

    Enabled by default if supported.

  • dv_esw_en parameter [int]

    A nonzero value enables E-Switch using Direct Rules.

    Enabled by default if supported.

  • 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).

  • mr_ext_memseg_en parameter [int]

    A nonzero value enables extending memseg when registering DMA memory. If enabled, the number of entries in MR (Memory Region) lookup table on datapath is minimized and it benefits performance. On the other hand, it worsens memory utilization because registered memory is pinned by kernel driver. Even if a page in the extended chunk is freed, that doesn’t become reusable until the entire memory is freed.

    Enabled by default.

  • representor parameter [list]

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

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

    For instance, to probe port representors 0 through 2:

    representor=[0-2]

  • 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.

  • sys_mem_en parameter [int]

    A non-zero value enables the PMD memory management allocating memory from system by default, without explicit rte memory flag.

    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.

35.5.4. Firmware configuration

Firmware features can be configured as key/value pairs.

The command to set a value is:

mlxconfig -d <device> set <key>=<value>

The command to query a value is:

mlxconfig -d <device> query | grep <key>

The device name for the command mlxconfig can be either the PCI address, or the mst device name found with:

mst status

Below are some firmware configurations listed.

  • link type:

    LINK_TYPE_P1
LINK_TYPE_P2
value: 1=Infiniband 2=Ethernet 3=VPI(auto-sense)

  • enable SR-IOV:

    SRIOV_EN=1

  • maximum number of SR-IOV virtual functions:

    NUM_OF_VFS=<max>

  • enable DevX (required by Direct Rules and other features):

    UCTX_EN=1

  • aggressive CQE zipping:

    CQE_COMPRESSION=1

  • L3 VXLAN and VXLAN-GPE destination UDP port:

    IP_OVER_VXLAN_EN=1
IP_OVER_VXLAN_PORT=<udp dport>

  • enable VXLAN-GPE tunnel flow matching:

    FLEX_PARSER_PROFILE_ENABLE=0
or
FLEX_PARSER_PROFILE_ENABLE=2

  • enable IP-in-IP tunnel flow matching:

    FLEX_PARSER_PROFILE_ENABLE=0

  • enable MPLS flow matching:

    FLEX_PARSER_PROFILE_ENABLE=1

  • enable ICMP(code/type/identifier/sequence number) / ICMP6(code/type) fields matching:

    FLEX_PARSER_PROFILE_ENABLE=2

  • enable Geneve flow matching:

    FLEX_PARSER_PROFILE_ENABLE=0
or
FLEX_PARSER_PROFILE_ENABLE=1

  • enable GTP flow matching:

    FLEX_PARSER_PROFILE_ENABLE=3

  • enable eCPRI flow matching:

    FLEX_PARSER_PROFILE_ENABLE=4
PROG_PARSE_GRAPH=1

  • enable realtime timestamp format:

    REAL_TIME_CLOCK_ENABLE=1

35.6. Prerequisites

This driver relies on external libraries and kernel drivers for resources allocations and initialization. The following dependencies are not part of DPDK and must be installed separately:

  • libibverbs

    User space Verbs framework used by librte_net_mlx5. This library provides a generic interface between the kernel and low-level user space drivers such as libmlx5.

    It allows slow and privileged operations (context initialization, hardware resources allocations) to be managed by the kernel and fast operations to never leave user space.

  • libmlx5

    Low-level user space driver library for Mellanox ConnectX-4/ConnectX-5/ConnectX-6/BlueField devices, it is automatically loaded by libibverbs.

    This library basically implements send/receive calls to the hardware queues.

  • Kernel modules

    They provide the kernel-side Verbs API and low level device drivers that manage actual hardware initialization and resources sharing with user space processes.

    Unlike most other PMDs, these modules must remain loaded and bound to their devices:

    • mlx5_core: hardware driver managing Mellanox ConnectX-4/ConnectX-5/ConnectX-6/BlueField devices and related Ethernet kernel network devices.
    • mlx5_ib: InfiniBand device driver.
    • ib_uverbs: user space driver for Verbs (entry point for libibverbs).

  • Firmware update

    Mellanox OFED/EN releases include firmware updates for ConnectX-4/ConnectX-5/ConnectX-6/BlueField adapters.

    Because each release provides new features, these updates must be applied to match the kernel modules and libraries they come with.

Note

Both libraries are BSD and GPL licensed. Linux kernel modules are GPL licensed.

35.6.1. Installation

Either RDMA Core library with a recent enough Linux kernel release (recommended) or Mellanox OFED/EN, which provides compatibility with older releases.

35.6.1.1. RDMA Core with Linux Kernel

  • Minimal kernel version : v4.14 or the most recent 4.14-rc (see Linux installation documentation)

  • Minimal rdma-core version: v15+ commit 0c5f5765213a (“Merge pull request #227 from yishaih/tm”) (see RDMA Core installation documentation)

  • When building for i686 use:

    • rdma-core version 18.0 or above built with 32bit support.
    • Kernel version 4.14.41 or above.

  • Starting with rdma-core v21, static libraries can be built:

    cd build
CFLAGS=-fPIC cmake -DIN_PLACE=1 -DENABLE_STATIC=1 -GNinja ..
ninja

35.6.1.2. Mellanox OFED/EN

  • Mellanox OFED version: 4.5 and above / Mellanox EN version: 4.5 and above
  • firmware version:
    • ConnectX-4: 12.21.1000 and above.
    • ConnectX-4 Lx: 14.21.1000 and above.
    • ConnectX-5: 16.21.1000 and above.
    • ConnectX-5 Ex: 16.21.1000 and above.
    • ConnectX-6: 20.27.0090 and above.
    • ConnectX-6 Dx: 22.27.0090 and above.
    • BlueField: 18.25.1010 and above.

While these libraries and kernel modules are available on OpenFabrics Alliance’s website and provided by package managers on most distributions, this PMD requires Ethernet extensions that may not be supported at the moment (this is a work in progress).

Mellanox OFED and Mellanox EN include the necessary support and should be used in the meantime. For DPDK, only libibverbs, libmlx5, mlnx-ofed-kernel packages and firmware updates are required from that distribution.

Note

Several versions of Mellanox OFED/EN are available. Installing the version this DPDK release was developed and tested against is strongly recommended. Please check the prerequisites.

35.7. Supported NICs

The following Mellanox 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
  • BlueField
  • BlueField-2

Below are detailed device names:

  • Mellanox® ConnectX®-4 10G MCX4111A-XCAT (1x10G)
  • Mellanox® ConnectX®-4 10G MCX412A-XCAT (2x10G)
  • Mellanox® ConnectX®-4 25G MCX4111A-ACAT (1x25G)
  • Mellanox® ConnectX®-4 25G MCX412A-ACAT (2x25G)
  • Mellanox® ConnectX®-4 40G MCX413A-BCAT (1x40G)
  • Mellanox® ConnectX®-4 40G MCX4131A-BCAT (1x40G)
  • Mellanox® ConnectX®-4 40G MCX415A-BCAT (1x40G)
  • Mellanox® ConnectX®-4 50G MCX413A-GCAT (1x50G)
  • Mellanox® ConnectX®-4 50G MCX4131A-GCAT (1x50G)
  • Mellanox® ConnectX®-4 50G MCX414A-BCAT (2x50G)
  • Mellanox® ConnectX®-4 50G MCX415A-GCAT (1x50G)
  • Mellanox® ConnectX®-4 50G MCX416A-BCAT (2x50G)
  • Mellanox® ConnectX®-4 50G MCX416A-GCAT (2x50G)
  • Mellanox® ConnectX®-4 50G MCX415A-CCAT (1x100G)
  • Mellanox® ConnectX®-4 100G MCX416A-CCAT (2x100G)
  • Mellanox® ConnectX®-4 Lx 10G MCX4111A-XCAT (1x10G)
  • Mellanox® ConnectX®-4 Lx 10G MCX4121A-XCAT (2x10G)
  • Mellanox® ConnectX®-4 Lx 25G MCX4111A-ACAT (1x25G)
  • Mellanox® ConnectX®-4 Lx 25G MCX4121A-ACAT (2x25G)
  • Mellanox® ConnectX®-4 Lx 40G MCX4131A-BCAT (1x40G)
  • Mellanox® ConnectX®-5 100G MCX556A-ECAT (2x100G)
  • Mellanox® ConnectX®-5 Ex EN 100G MCX516A-CDAT (2x100G)
  • Mellanox® ConnectX®-6 200G MCX654106A-HCAT (2x200G)
  • Mellanox® ConnectX®-6 Dx EN 100G MCX623106AN-CDAT (2x100G)
  • Mellanox® ConnectX®-6 Dx EN 200G MCX623105AN-VDAT (1x200G)
  • Mellanox® ConnectX®-6 Lx EN 25G MCX631102AN-ADAT (2x25G)

35.8. Quick Start Guide on OFED/EN

  1. Download latest Mellanox OFED/EN. For more info check the prerequisites.

  2. Install the required libraries and kernel modules either by installing only the required set, or by installing the entire Mellanox OFED/EN:

    ./mlnxofedinstall --upstream-libs --dpdk

  3. Verify the firmware is the correct one:

    ibv_devinfo

  4. Verify all ports links are set to Ethernet:

    mlxconfig -d <mst device> query | grep LINK_TYPE
LINK_TYPE_P1                        ETH(2)
LINK_TYPE_P2                        ETH(2)

    Link types may have to be configured to Ethernet:

    mlxconfig -d <mst device> set LINK_TYPE_P1/2=1/2/3

* LINK_TYPE_P1=<1|2|3> , 1=Infiniband 2=Ethernet 3=VPI(auto-sense)

    For hypervisors, verify SR-IOV is enabled on the NIC:

    mlxconfig -d <mst device> query | grep SRIOV_EN
SRIOV_EN                            True(1)

    If needed, configure SR-IOV:

    mlxconfig -d <mst device> set SRIOV_EN=1 NUM_OF_VFS=16
mlxfwreset -d <mst device> reset

  5. Restart the driver:

    /etc/init.d/openibd restart

    or:

    service openibd restart

    If link type was changed, firmware must be reset as well:

    mlxfwreset -d <mst device> reset

    For hypervisors, after reset write the sysfs number of virtual functions needed for the PF.

    To dynamically instantiate a given number of virtual functions (VFs):

    echo [num_vfs] > /sys/class/infiniband/mlx5_0/device/sriov_numvfs

  6. Install DPDK and you are ready to go. See compilation instructions.

35.9. Enable switchdev mode

Switchdev mode is a mode in E-Switch, that binds between representor and VF. Representor is a port in DPDK that is connected to a VF in such a way that assuming there are no offload flows, each packet that is sent from the VF will be received by the corresponding representor. While each packet that is sent to a representor will be received by the VF. This is very useful in case of SRIOV mode, where the first packet that is sent by the VF will be received by the DPDK application which will decide if this flow should be offloaded to the E-Switch. After offloading the flow packet that the VF that are matching the flow will not be received any more by the DPDK application.

  1. Enable SRIOV mode:

    mlxconfig -d <mst device> set SRIOV_EN=true

  2. Configure the max number of VFs:

    mlxconfig -d <mst device> set NUM_OF_VFS=<num of vfs>

  3. Reset the FW:

    mlxfwreset -d <mst device> reset

  1. Configure the actual number of VFs:

    echo <num of vfs > /sys/class/net/<net device>/device/sriov_numvfs

  2. Unbind the device (can be rebind after the switchdev mode):

    echo -n "<device pci address" > /sys/bus/pci/drivers/mlx5_core/unbind

  3. Enable switchdev mode:

    echo switchdev > /sys/class/net/<net device>/compat/devlink/mode

35.10. 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

    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.

35.11. Rx burst functions

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

Table 35.1 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

35.12. Supported hardware offloads

Table 35.2 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 35.3 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
RSS shared action

N/A
DPDK 20.11
OFED 5.2
rdma-core 33
ConnectX-5
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
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
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
Sampling
DPDK 20.11
OFED 5.1-2
rdma-core 32
ConnectX-5
DPDK 20.11
OFED 5.1-2
N/A
ConnectX-5
Age shared action
DPDK 20.11
OFED 5.2
rdma-core 32
ConnectX-6 Dx
DPDK 20.11
OFED 5.2
rdma-core 32
ConnectX-6 Dx

35.13. 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.

35.14. 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.

35.15. 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

35.16. Usage example

This section demonstrates how to launch testpmd with Mellanox 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:

    echo 1024 > /sys/kernel/mm/hugepages/hugepages-2048kB/nr_hugepages/nr_hugepages

  5. Start testpmd with basic parameters:

    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>

35.17. 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:
    testpmd> flow dump <port> <output_file>
    • call rte_flow_dev_dump api:
    rte_flow_dev_dump(port, 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>