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SubjectRe: Macintosh kernel out

On Tue, 28 May 1996, Mike Castle wrote:
> Amazingly enough Linus Torvalds said:
> > it). It results in good context switch numbers, though, because you don't have
> > to switch the page tables or invalidate the TLB. It also means that you can
> Can this be/ is this accomplished with linux and cloned
> processes?

Yes. Cloned processes do not get the TLB switch overhead, so expect to
see good context switch times if you want to try it out. However, there
are obviously other issues here too, and if you disregard inter-process
memory protection issues like QNX does then you can make _other_ things
faster too - it's not just the TLB invalidation that costs you.

(For example, the kernel entry can be much cheaper if you know there are
no protection issues to worry about etc etc)

So expect switches between cloned processes to be faster, but don't
expect them to be no cost at all. The fastest way to context switch is
always to do it from user mode directly.


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