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SubjectRe: [uPATCH] SMP scheduling fix (?)
Hi!

> I'd _really_ like to have a nice value that says "don't run unless you
> are twiddling your thumbs". Ie a nice 20 perhaps, that says I don't
> want

I'd like that, too.

But it is currently impossible with linux: it opens DoS attack.

make your nice 20 task hold some lock, and then run 'normal' task so
that nice 20 task will never ever get cpu again. BOom, you are holding
lock and are not going to release it.

Is there solution to this? Maybe processes running in kernel get
automagical priority boost? Or at least every nice 20 process
entering kernel gets promoted to nice 19 level which does not have
that "run only iff idle" property. Unfortunately, this would slow
syscall path...

...thinking about it, scheduler knows if task is in kernel or not, can
easily test that and dishonor 'nice 20', if task runs in kernel mode.

Pavel
--
I'm really pavel@atrey.karlin.mff.cuni.cz. Pavel
Look at http://atrey.karlin.mff.cuni.cz/~pavel/ ;-).

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