>The problem was (and has always been) the hefty context loading operation
>in ctx_alloc() on sun4c MMUs (which was carefully placed outside the
>splpmap/splx scope, so changing just the definition splpmap() did not
>have any effect. splpmap can probably be omitted entirely from ctxalloc()
>anyway).

I'm new here. Could you explain what you mean by "hefty context loading
operation?" My understanding is that the two things a multitasking machine
MUST do well are context switches and job scheduling. To some extent
context switches are products of the register file structure of the
processor which is why some chips can perform context switches with less
performance cost than others.

I understood that the SPARC, having been designed from the very beginning
to run a multitasking OS, actually has a fairly efficient context switch?
Is the problem above a 
Sun or a NetBSD problem? Shouldn't the context switch code be highly
optimised because
of the number of times it gets called?

Just curious.

Fletch




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>-pk
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