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SubjectRe: low priority soft RT?
On Tue, Jul 27, 1999 at 06:00:11AM +0100, 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.

I still don't understand the purpose of SCHED_IDLE. It seems as if the only purpose
is to slow down general execution by a couple of percent in order to make it appear
as if the lowest priority tasks are not using any cpu time -- that is to shift the cost
of lowest priority tasks from running those tasks to general kernel lock management code.

Someone, maybe it was Linus, pointed out that the current range of "nice" levels is totally
arbitrary and simply increasing the range would do good.


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