32. SZEDATA2 poll mode driver library

32.1. Prerequisites

This PMD requires kernel modules which are responsible for initialization and allocation of resources needed for sze2 layer function. Communication between PMD and kernel modules is mediated by libsze2 library. These kernel modules and library are not part of DPDK and must be installed separately:

• libsze2 library

  The library provides API for initialization of sze2 transfers, receiving and transmitting data segments.

• Kernel modules

  • combo6core
  • combov3
  • szedata2
  • szedata2_cv3 or szedata2_cv3_fdt

  Kernel modules manage initialization of hardware, allocation and sharing of resources for user space applications.

Information about getting the dependencies can be found here.

32.2. Configuration

These configuration options can be modified before compilation in the .config file:

• CONFIG_RTE_LIBRTE_PMD_SZEDATA2 default value: n

  Value y enables compilation of szedata2 PMD.

32.3. Using the SZEDATA2 PMD

From DPDK version 16.04 the type of SZEDATA2 PMD is changed to PMD_PDEV. SZEDATA2 device is automatically recognized during EAL initialization. No special command line options are needed.

Kernel modules have to be loaded before running the DPDK application.

32.4. NFB card architecture

The NFB cards are multi-port multi-queue cards, where (generally) data from any Ethernet port may be sent to any queue. They were historically represented in DPDK as a single port.

However, the new NFB-200G2QL card employs an addon cable which allows to connect it to two physical PCI-E slots at the same time (see the diagram below). This is done to allow 200 Gbps of traffic to be transferred through the PCI-E bus (note that a single PCI-E 3.0 x16 slot provides only 125 Gbps theoretical throughput).

Since each slot may be connected to a different CPU and therefore to a different NUMA node, the card is represented as two ports in DPDK (each with half of the queues), which allows DPDK to work with data from the individual queues on the right NUMA node.

Fig. 32.2 NFB-200G2QL high-level diagram

32.5. Limitations

The SZEDATA2 PMD does not support operations related to Ethernet ports (link_up, link_down, set_mac_address, etc.).

NFB cards employ multiple Ethernet ports. Until now, Ethernet port-related operations were performed on all of them (since the whole card was represented as a single port). With NFB-200G2QL card, this is no longer viable (see above).

Since there is no fixed mapping between the queues and Ethernet ports, and since a single card can be represented as two ports in DPDK, there is no way of telling which (if any) physical ports should be associated with individual ports in DPDK.

32.6. Example of usage

Read packets from 0. and 1. receive channel and write them to 0. and 1. transmit channel:

$RTE_TARGET/app/testpmd -l 0-3 -n 2 \
-- --port-topology=chained --rxq=2 --txq=2 --nb-cores=2 -i -a

Example output:

[...]
EAL: PCI device 0000:06:00.0 on NUMA socket -1
EAL:   probe driver: 1b26:c1c1 rte_szedata2_pmd
PMD: Initializing szedata2 device (0000:06:00.0)
PMD: SZEDATA2 path: /dev/szedataII0
PMD: Available DMA channels RX: 8 TX: 8
PMD: resource0 phys_addr = 0xe8000000 len = 134217728 virt addr = 7f48f8000000
PMD: szedata2 device (0000:06:00.0) successfully initialized
Interactive-mode selected
Auto-start selected
Configuring Port 0 (socket 0)
Port 0: 00:11:17:00:00:00
Checking link statuses...
Port 0 Link Up - speed 10000 Mbps - full-duplex
Done
Start automatic packet forwarding
  io packet forwarding - CRC stripping disabled - packets/burst=32
  nb forwarding cores=2 - nb forwarding ports=1
  RX queues=2 - RX desc=128 - RX free threshold=0
  RX threshold registers: pthresh=0 hthresh=0 wthresh=0
  TX queues=2 - TX desc=512 - TX free threshold=0
  TX threshold registers: pthresh=0 hthresh=0 wthresh=0
  TX RS bit threshold=0 - TXQ flags=0x0
testpmd>