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Perhaps you think DPDK (Data Plane Development Kit) is a high-speed data-movement standard that’s strictly for networking applications. Perhaps you think DPDK is an Intel-specific specification. Perhaps you think DPDK is restricted to the world of host CPUs and ASICs. Perhaps you’ve never heard of DPDK—given its history, that’s certainly possible. If any of those statements is correct, keep reading this post.
Originally, DPDK was a set of data-plane libraries and NIC (network interface controller) drivers developed by Intel for fast packet processing on Intel x86 microprocessors. That is the DPDK origin story. Last April, DPDK became a Linux Foundation Project. It lives at DPDK.org and is now processor agnostic.
DPDK consists of several main libraries that you can use to:
- Send and receive packets while minimizing the number of CPU cycles needed (usually less than 80)
- Develop fast packet-capture algorithms
- Run 3rd-party fast-path stacks
So far, DPDK certainly sounds like a networking-specific development kit but, as Atomic Rules’ CTO Shep Siegel says, “If you can make your data-movement problem look like a packet-movement problem,” then DPDK might be a helpful shortcut in your development process.
Siegel knows more than a bit about DPDK because his company has just released Arkville, a DPDK-aware FPGA/GPP data-mover IP block and DPDK PMD (Poll Mode Driver) that allow Linux DPDK applications to offload server cycles to FPGA gates in tandem with the Linux Foundation’s 17.05 release of the open-source DPDK libraries. Atomic Rules’ Arkville release is compatible with Xilinx Vivado 2017.1 (the latest version of the Vivado Design Suite), which was released in April. Currently, Atomic rules provides two sample designs:
- Four-Port, Four-Queue 10 GbE example (Arkville + 4×10 GbE MAC)
- Single-Port, Single-Queue 100 GbE example (Arkville + 1×100 GbE MAC)
(Atomic Rules’ example designs for Arkville were compiled with Vivado 2017.1 as well.)
These examples are data movers; Arkville is a packet conduit. This conduit presents a DPDK interface on the CPU side and AXI interfaces on the FPGA side. There’s a convenient spot in the Arkville conduit where you can add your own hardware for processing those packets. That’s where the CPU offloading magic happens.
Atomic Rules’ Arkville IP works well with all Xilinx UltraScale devices but it works especially well with Xilinx UltraScale+ All Programmable devices that provide two integrated PCIe Gen3 x16 controllers. (That includes devices in the Kintex UltraScale+ and Virtex UltraScale+ FPGA families and the Zynq UltraScale+ MPSoC device families.)
Why?
Because, as BittWare’s VP of Network Products Craig Lund says, “100G Ethernet is hard. It’s not clear that you can use PCIe to get [that bit rate] into a server [using one PCIe Gen3 x16 interface]. From the PCIe specs, it looks like it should be easy, but it isn’t.” If you are handling minimum-size packets, says Lund, there are lots of them—more than 14 million per second. If you’re handling big packets, then you need a lot of bandwidth. Either use case presents a throughput challenge to a single PCIe Root Complex. In practice, you really need two.
BittWare has implemented products using the Atomic Rules Arkville IP, based on its XUPP3R PCIe card, which incorporates a Xilinx Virtex UltraScale+ VU13P FPGA. One of the many unique features of this BittWare board is that it has two PCIe Gen3 x16 ports: one available on an edge connector and the other available on an optional serial expansion port. This second PCIe Gen3 x16 port can be connected to a second PCIe slot for added bandwidth.
However, even that’s not enough says Lund. You don’t just need two PCIe Gen3 x16 slots; you need two PCIe Gen2 Root Complexes and that means you need a 2-socket motherboard with two physical CPUs to handle the traffic. Here’s a simplified block diagram that illustrates Lund’s point:
BittWare’s XUPP3R PCIe Card has two PCIe Gen3 x16 ports: one on an edge connector and the other on an optional serial expansion port for added bandwidth
BittWare has used its XUPP3R PCIe card and the Arkville IP to develop two additional products:
- StreamSleuth, a 100GbE network packet-processing appliance (see “Danger: 100GbE! BittWare’s StreamSleuth safely processes packets at 100Gbps using FPGA hardware acceleration from [guess who]”)
- StreamSurge, a 1U box with a liquid-cooled Intel E5 v4 single-socket server and the company’s XUPP3R PCIe card configured as a NIC using BittWare’s StreamSurge IP.
Note: For more information about Atomic Rules’ IP and BittWare’s XUPP3R PCIe card, see “BittWare’s UltraScale+ XUPP3R board and Atomic Rules IP run Intel’s DPDK over PCIe Gen3 x16 @ 150Gbps.”
Arkville is a product offered by Atomic Rules. The XUPP3R PCIe card is a product offered by BittWare. Please contact these vendors directly for more information about these products.
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June 6, 2017 at 04:32PM