Con Kolivas [interview] posted a set of patches to the lkml offering a pluggable cpu scheduler framework. He began, "with the recent interest in varying the cpu schedulers in linux, this set of patches provides a modular framework for adding multiple boot-time selectable cpu schedulers. William Lee Irwin III [interview] came up with the original design and I based my patchset on that." The architecture independent framework is designed to allow new schedulers to be added by only touching three files, without adding overhead, and allowing you to compile in only the CPU scheduler(s) you need. Con explained, "this allows, for example, embedded hardware to have a tiny new scheduler that takes up minimal code space."
Designer of the 2.6 kernel's O(1) scheduler, Ingo Molnar [interview], had some reservations. He said, "my main worry with this approach is not really overhead but the impact on scheduler development. Right now there is a Linux scheduler that every developer (small-workload and large-workload people) tries to make as good as possible." This includes all corner cases, from the smallest embedded hardware to the largest NUMA hardware, with all their improvements benefiting the core CPU scheduler. Ingo added, "we want to make it _harder_ for specialized workloads to be handled in some 'specialized' way, because those precise workloads do show up in other workloads too, in a different manner. A fix made for NUMA or real-time purposes can easily make a difference for desktop workloads. Often 'specialized' is an excluse for a 'fundamentally broken, limited hack', especially in the scheduler world."