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Preemptible Linux Kernel: Interviews and Info
An anonymous submitter sends: "MontaVista and Robert Love are developing a patch for the Linux kernel to make it fully preemptible. Lots of users are involved, and tests show huge reductions in latency. Robert's kernel patches are here. Finally, an interview with Robert, on preemption and more."
Really? That's the first time I hear about that.
;-)
There is a difference between pre-emptive multitasking and pre-emptible kernel.
Pre-emptive multitasking means that the kernel can interrupt any thread and give control to another thread, so that a thread cannot hog the CPU resources. This is what all modern operating systems do, except Windows 3.1/9x/Me and MacOS (pre- X), though it could be argued that Windows 3.1/9x/Me is not an operating system much less a modern one
Pre-emptible kernel is a different beast. It means that the kernel can interrupt itself (i.e. a thread running in the kernel mode) and give control to another thread running in the kernel mode. This is used in real-time operating systems where you need to have a guaranteed maximum response time (i.e. a thread must not wait longer than a certain amount of time before it gets control). However, this is not all that useful for general-purpose OSes and may even be detrimental to servers, where throughput matter more than response time. So it's good to know that this will be a compile-time option.
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If you think big enough, you'll never have to do it.
Linus himself said, that they should rather fix the CAUSE of those latencies instead of the symptoms.
Isn't that like saying that you'd rather fix all buggy applications instead of providing a protected memory environment?