Kernel Bypass & Offload Introduction

System network optimization can be done in two ways: 1 bypass the kernel (bypass), 2 with hardware replacement software (offload).

Details include:

1. Bypass the kernel:

• does not use kernel kernel subsystem functions, using the same functionality as the code of their own implementation of the processing.
• Direct access to and control of device memory from user space-avoids copying data from the device to the kernel and then copying it from the kernel to the user space.

2. Replace with hardware:

• Replace some of the functionality of the software with a dedicated hardware device.
• Typical examples of hardware replacement software are: DMA engines, GPUs, Rendering screens, cryptography, TOE (TCP offload engines).

Why do you have to work on two fronts? The main reasons can be attributed to:

1. UNIX is designed and optimized, and its main task now is to support multiple processes running concurrently, and to avoid any process being suspended for a long time because of lack of resources. But in the field of high-frequency trading, we want certain processes to handle each message with fast response times, low latency fluctuations, and no need for the average performance of all processes on the machine.

2. The TCP/IP protocol stack is optimized to prevent link loss and effective bandwidth utilization.

There are already a lot of mature solutions available, and they are:

• Ntop.org DNA
• Netmap
• Intel DPDK
• myricom sniffer10g and DBL
• 6WINDGate
• Solarflare Openonload
  
• Napatech
  

Each of these solutions has their own solution.

• Custom device drivers: Netmap and DNA Add the I/O memory to user-space mappings based on standard Intel drivers.
• Custom hardware. Myricom and Napatech have their own custom-made hardware and the corresponding driver (myricom with ASIC, Napatech with FPGA).
• A library of user space. Each of these solutions provides a library for accessing their extended functionality. These features vary enormously: Ethernet I/O, libpcap compatibility, hardware-assisted message packet distribution for multi-process processing, cache management, and the entire TCP/IP layer functionality.
• Licensing. Netmap is open source, and the DNA user base needs a modest license. Napatech requires an NDA and relies on expensive hardware.

Reference article:

Http://ttthebear.blogspot.com/2008/07/linux-kernel-bypass-and-performance.html

<kernel in the Bypass and offload technologies>--Christoph Lameter

http://lukego.github.io/blog/2013/01/04/kernel-bypass-networking/

Kernel Bypass & Offload Introduction