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SubjectRe: low priority soft RT?
(note new email address)

Stephen C. Tweedie wrote:
> There's a much, much easier way --- just revoke the SCHED_IDLE
> scheduling class when a process explicitly calls schedule(). That
> automatically takes care of every single case where a process gives up
> the CPU from inside the kernel. The only special case then becomes the
> schedule inside return_to_user, where we want to keep SCHED_IDLE
> intact.
>
> However, that adds code to two of the hottest paths in the whole
> kernel. Not nice.

Then perhaps the best compromise is to make SCHED_IDLE a compile
time option. If you want to support "true" SCHED_IDLE you must take
the performance hit in schedule() to be safe from lock starvation.
If you don't compile "true" SCHED_IDLE into the kernel it would
just get mapped to be the same as 'nice 19' or whatever.

-Mitch

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