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SubjectRe: 4MB pages and framebuffer access, x11perf results, 2.1.125

On Wed, 28 Oct 1998, Linus Torvalds wrote:

> On Thu, 29 Oct 1998, MOLNAR Ingo wrote:
> >
> > the 4m issue is i think conceptually a granularity thing. Theres nothing
> > wrong with unmapping the middle 4M of a 12M framebuffer mapping, no matter
> > how rare it would be.
>
> There _is_ something wrong with it - namely that the VM layer has to know
> how. [...]

theres one more reason why it's a granularity type of thing: the vma's
virtual address has to be 4M aligned too. Basically mmap() picks a generic
4M-size vma, and only the driver-specific function knows that this is
'incorrect'. We could hack this around by dropping the vma and
reallocating it, but this is not quite robust.

-- mingo



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