Linux Plumbers Conf 2009

Networking is the key plumbing component that connects users and services to the world. Even in the embedded world, connectivity is critically important. Therefore a new microconf has been added to Linux Plumbers Conference to cover hot topics in Networking.

Most people familiar with the Linux will recognize Stephen Hemminger as one of the key current developers of Linux networking. He has made many important contributions to many components of Linux’s networking stack for several years. We are fortunate that he has graciously agreed to run the Networking micro-conference.

The opening part of the session deals with the interfaces to some of the core components of the networking stack. Obviously, if everything was working perfectly, there would be no need for a conference; therefore the two API’s under discussion are both important but incomplete.

The first topic is the wireless networking API. Linux is now undergoing a renaissance in wireless development. After going through the dark ages with many hardware devices not supported, and competing 802.11 protocol stacks; developers and companies are now focusing on delivering a complete and compatible solution. The first speaker John Linville is the current wireless networking maintainer and his talk “Modern Configuration API for Wireless Networking” covers the maturing cfg80211 API that is replacing the classical, outdated and scorned wireless extensions interface. Fully adopting cfg80211 will require coordinated changes to both the kernel and user utilities, which we hope that Plumbers can help with.

The second API-related talk covers network namespaces, a developing technology which provides controlled views of the networking environment to containerized processes. Projects like OpenVZ have use network namespaces for some time, but getting this technology into the mainline kernel has been a multi-year process which is still ongoing. Like other virtual environments, network namespaces bring their own communications challenges. The talk, “Why Network Namespace Sucks and How to Make it Suck Faster”, by Pavel Emelyanov will deal with some of these issues. It turns out that the Linux kernel has no fewer than five network device types that can be used as packet sources, with a sixth residing in the OpenVZ project. Pavel will compare and contrast these devices with an eye to future directions.

The miniconf will feature two talks on the processing of incoming network packets; proper received-packet processing is critical to networking performance on modern multi-core/multi-thread/multi-interrupt hardware. By looking at this problem from two different points of view, we hope some synergy will happen in this area.

The first performance talk is “Receive Packet Steering: A Software Solution to Scaling the Network Receive Path” by Tom Herbert. Tom notes that networking receive scalability is often limited by the single receive queue provided by older network interface controllers (NICs). This situation motivates some way of introducing parallelism in the receive path in spite of the single receive queue. If additional parallelism could be introduced into the single-queue receive path, there would be a valuable opportunity to increase performance on these older controllers.

The second performance oriented talk is on the new threaded interrupts “Threaded Network Device Interrupts” by Steven Rostedt. Steven argues that the use of threaded interrupts will not only simplify the networking code, but also increase network throughput. Given that some prominent developers in the networking community have been expressed skepticism about the value of threaded interrupts, we can expect some spirited discussion, and perhaps some modifications to threaded interrupts, to networking, or both.