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Re: Rep:Re: [f-cpu] virtually or physically-addressed cache ?

From: "Michael Riepe" <michael@stud.uni-hannover.de>

> The main drawback is that you'll have to know the number of processes and
> the maximum total memory size in advance. You can do that in an embedded
> system (works pretty well there), but not in a general-purpose OS.

There is a difference between what you can do and what you can efficiently
do. In such a scheme if you have say a 48 bit global address space and you
are using 32 bit addresses with byte addressing you can efficiently run 65K
processes with 2 GB address spaces each, that is not to say you cant run
more you will just have to make changes in the global address space and
either flush the cache or walk it to invalidate affected cachelines each
time a process not on the list is "swapped" in. Would even a hard limit of
65K 4GB address spaces really present any issue for a general purpose OS
though? :)


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