Subject: Re: Add a MAP_ALIGNED flag for mmap(2).
To: der Mouse <mouse@Rodents.Montreal.QC.CA>
From: Andrew Brown <firstname.lastname@example.org>
Date: 03/03/2003 16:34:45
>>> PMAP_PALIGN Request page alignment. The returned region will
>>> be page-aligned.
>> Regions returned by mmap are *always* page aligned.
>...at present. But is that part of mmap()'s interface contract, or is
>it an accident of the implementation?
>If it's part of the interface contact, it should be documented; if not,
>the above is not, IMO, an appropriate response to the proposed flag.
while you can request a mapping of something that spans only 123
bytes, it will use up a page. the page is the discrete unit with
which the vm system deals. if you could deal with smaller units,
those would be called pages.
you can also request a mapping of something 123 bytes into the object.
in that case, you'll get back an address from mmap(2) that's 123 bytes
off from the start of a page, but the entire page is mapped.
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