Re: unmap() sometimes unmaps more pages than specified

[Frank Mehnert]
> Hi,
> in a complex scenario I observed that the unmap() syscall sometimes
> flushes more pages than specified. So far I could not find a small
> testcase and therefore have to provide tracelogs of my current
> scenario:

[...]

> Please tell me if you need more information.

What happened in this scenario was that you had a 4MB mapping that had
two 4KB mappings mapped into the destination space.  You tried to
unmap a 4KB mapping in the source space, but there was only a 4MB
mapping there.  The whole 4MB mapping was as such unmapped instead.

The policy used to be different for early implementations; i.e.,
instead of unmapping the 4MB page the whole unmap operation was
ignored.  Completely ignoring the operation is not a good idea,
though.

	eSk