Re: more Re: Low memory problems in 8xx Linux

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"Peter" == Peter Allworth [off-list ref] writes:

Peter> Jesper Skov wrote: <snip>

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An alternative and slighly faster implementation might be to skip
the _PAGE_PRESENT check. Any reason something like this wouldn't
work?

Peter> <snip>

Peter> I had another look at the code and I now remember my rationale
Peter> for the _PAGE_PRESENT test. It wasn't to do with level 1 table
Peter> entries, Dan's code already takes care of that. It was so that
Peter> a zeroed pte couldn't get changed to a non-zero value, since
Peter> that would make the pte_none() function return the wrong
Peter> result. (Moreover, it just seemed wrong to mess with something
Peter> that's marked "invalid".)

Peter> Admittedly I'm being a bit paranoid since the next thing the
Peter> exception handler is likely to do is set the page table entry
Peter> to something valid.  But, can you be sure? What about a
Peter> segmentation fault? ;)

No, sounds sensible.

Jesper

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