SCHED_ULE should not be the default

[C. P. Ghost]

On Thu, Dec 15, 2011 at 10:44 AM, Tom Evans <tevans.uk at googlemail.com> wrote:
> Real time scheduler changing would be insane! I was thinking that
> both/any/all schedulers could be compiled into the kernel, and the
> choice of which one to use becomes a boot time configuration. You
> don't have to recompile the kernel to change timecounter.

Right.

Switching the scheduler on the fly may be thinkable though.
I could imagine a syscall that would suspend all scheduling,
convert the bookkeeping data of one scheduler into the other
scheduler's, and transfer control to the other scheduler. Of
course, that would require some heavy hacking, as I would
imagine that "cross-scheduler surgery" would result in a pretty
hard to debug kernel (at least during development).

A more general solution could even be a separate userland
scheduler process a la L4 [*], but since we don't have lightweight
IPC in the kernel (yet, or never), it would require even heavier
black wizardry. But nice and flexible it would be. ;-)

[*] Refs:
- https://github.com/l4ka/pistachio
- http://www.systems.ethz.ch/education/past-courses/fall-2010/aos/lectures/wk13-scheduling-print.pdf

Regards,
-cpghost.

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