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SubjectRe: the value of PROC_CHANGE_PENALTY


On Mon, 4 Jun 2001, Mark Hahn wrote:

> > am I correct ?
> > and if so, is this what the authors meant, or did they simply forget
> > to update PROC_CHANGE_PENALTY's value when moving from 2.2 to 2.4 ?
>
> I don't believe anyone has proposed a relation between nice
> and cpu-affinity; the latter has always been a fairly arbitrary
> constant.

I see, but even so, in linux-2.2 this arbitrary constant allows a non
realtime task to migrate, and totally prohibits it in linux-2.4 (unless
some other cpu is idle).
i.e. maybe there is no relation between the max value of the static
priority and PROC_CHANGE_PENALTY, but you get a scheduler that behaves
quite differently when you change one without the other.

I think that if it's indeed an arbitrary value, then it should have
been modified along with the modification of the quantum's length,
because this way the 2.2 behavior (which I assume somebody adopted for
a reason) would have remained the same.

However, if you say that PROC_CHANGE_PENALTY does somehow embody the
cpu-time wasted because of migration (due to cache etc.) regardless of
the quantum's length, then PROC_CHANGE_PENALTY should probably remain
the same and I got my answer.

Is this what you mean ?

thanks, Dan.


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