Re: MOL-MMU (WAS: Power Management)

[Michael Schmitz <schmitz@zirkon.biophys.uni-duesseldorf.de>]

> >
> >Thanks; I still see a potential problem with MMU context allocation here:
> >Paul's new code uses a bitmap to keep track of contexts in use
> >(context_map). MOL ignores this bit and just keeps allocating contexts by
> >relying on next_mmu_context to be unused (which it should be, most
> >of the time), plus the next one also being unused. Is that always
> >guaranteed? 
> 
> The MOL developer tree contains the necessary fixes:

That's the one I lookes at ...
> 
> Basically, MOL uses a different range of context than the
> kernel (due to the context bitmap, only 32.000 contexts are
> used by the kernel so a lot of the contexts are free for MOL).

OK, I wasn't sure that was what the mol vs. Linux contexts meant. Cleaner
and simpler than atomically checking for two unused contexts at once. I'll
give it a shot as soon as mozilla-cvs has finished building. 
 
> >And what's the penalty on using a context ID that's already in use?
> That would be very bad. From experience, the symptom is a lot
> of segfaults (but the kernel could go down too).

Mine just locked hard (both with and without checking for two consecutive
free context numbers), bad enough.

	Michael