Re: unmap() sometimes unmaps more pages than specified

On Thursday 22 June 2006 14:11, Espen Skoglund wrote:
> Uh... some confusion here.  Does f=0 here mean unmap and f=1 mean
> flush?  Let's try to clear it up:

I denoted the f bit of the control word in the unmap() syscall.

> You have two spaces A and B.  A has a 4MB page mapping.  B has
> received a 4KB page mapping from A.  Currently we have:
>
>   (1)  A.Flush(4K) == A.Flush(4M) since A has a 4MB mapping.
>   (2)  Likewise A.Unmap(4K) == A.Unmap(4M) since A has a 4MB mapping.
>   (3)  B.Flush(4K) is fine since B has a 4KB mapping.
>   (4)  Consequently A.Unmap(4K) != B.Flush(4K).
>
> I guess (4) is what you find difficult to handle, right?  This would
> work fine if (2) was not the case.  Currently the implementation does

Exactly!

> (obviously) not behave this way.  I'll give some thought to how this
> could most easily be handled.  The behaviour also raises some
> questions about the semantics of resetting/reading reference bits, but
> I think this could possibly be sorted out.

Would greatly appreciate if that issue could be handled. I will prevent
4M mappings in my scenario so far.

Thanks in advance,

Frank
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