> Correct, you waste PAGE_SIZE - USPACE bytes. Not a big deal, but
> I added the NOREDZONE option for small-memory systems to avoid this.

I guess it is pageable memory - unlike some other items allocated
per process...
Gets a bit more expensive with 8k pages.

> > Do we stack switch for ISRs anyway? I could grep for it...
> 
> i386 does not switch stacks for ISRs. The only way to switch
> stacks on a trap or interrupt is to use a TSS gate, and they
> are more expensive than normal trap gates. I only set up
> the double fault handler with a TSS gate, since it's fatal
> anyway, enabling it to switch stacks and have DDB make sense
> of it all.

Yes - I've often wondered if anyone ever used the x86 task stuff.
I half thought about using it for segment bounds on a 286,
but it was all to complex and costly.

I did notice (in the PIII boook?) some fast method of switching
from user to system mode.  Looked almost, but not quite, useful :-)

	David

-- 
David Laight: david@l8s.co.uk