Sidestep Kernel with RDMA

Remote Direct Memory Access - or RDMA for short - allows machines to access memory of other machines without going through the operating system kernel.  

This is a traditional computer science trick - if you have an abstraction in the way of your objective, bypass the abstraction.

The idea is to get performance improvement - low latency and high throughput. Sometimes these tricks come under the label of "ultra-low-latency software development" or "ultra low latency techniques".

The goal is zero-copy (or near-zero-copy) data transfer - data moves between memory buffers directly. 

Key benefits include:

• Skipping kernel involvement
• Avoid creation of multiple intermediate copies
• Avoid switching between kernel space and user space

Protocols to support this include:

• InfiniBand
• RoCE (RDMA over Converged Ethernet)
• iWARP (RDMA over TCP/IP).

Protocols need to be supported at the OS level. Microsoft Windows Server 2012 onwards for example support iWARP.

Kernel Bypass Networking

Kernel bypass networking is a technique to improve network performance by enabling applications to interact with network hardware directly, instead of going via an abstraction layer (the OS kernel's network stack).  

All intermediate abstractions are bypassed. 

There are various specialized libraries such as DPDK, RDMA and OpenOnload to access Network Interface Cards (NICs) directly.