Multicore networking in Linux user space with no performance overhead

Dronamraju Subramanyam, John Rekesh and Srini Addepalli, Freescale Semiconductor

February 26, 2012

Dronamraju Subramanyam, John Rekesh and Srini Addepalli, Freescale Semiconductor

A zero-overhead user space network software framework
Multi-core SoCs software developers have been challenged with writing applications that suit specific SoC families and their derivatives. This means writing specialized code that is suitable and specific to a given SoC.

For example queuing, buffer management, statistics, accelerators and other technologies would have very specific modus operandi that applications must follow. There would also be specific methods of interfacing with the hardware to receive and send packets, and for distributing work.

These also result in application software architecture being dictated to some extent by the SoC. Migrating software across SoCs, even within the family of the same SoC product line can be a large and expensive development effort, and a burden on maintenance and support.

There is a need for a software framework that is able to leverage features provided by a multicore SoC, without the need for in-depth expertise in the hardware operational understanding.

Applications need to be portable, and be able to leverage different SoCs and families without software application changes, essentially through configuration of features and an abstracted execution environment.

Much like a traditional (i.e. non-embedded) operating system that hides many hardware details from applications, a network software framework that hides SoC specific details and offers a consistent programming model to applications is the need of the hour.

Limits of Linux in the dataplane
Direct use of Linux kernel for data plane implementations has limitations. Linux kernels provide abstraction for disk I/O, USB, processor features and other hardware elements. However, scaling to millions of flows/sessions in datapath is not easy in the Linux kernel space. Kernel resident applications suffer from limited memory, an environment that is hard to develop and debug in. Vendors also have GPL concerns with Linux kernel modules.

In order to overcome the limitations of Linux, it is required to execute applications in user-space with virtually zero-overhead and with direct access to the SoC hardware, and provide a software framework, which caters to various needs of networking applications without requiring knowledge of hardware specific details.

Such a framework needs to support layer 2, layer 3 and higher layer processing, orchestrate packet flow, manage packet buffers, provide access to hardware accelerators, timers, and statistics.

It also needs to support inter-application communication, and provide multiple execution models for applications. A network software framework in user-space that leverages the advantages of Linux OS and overcomes its limitation for networking and embedded application is essential for next generation of networking and embedded applications.