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SubjectRe: Cache incoherencies
On Fri, 27 Aug 1999, Rogier Wolff wrote:
> gfp returns a page from a pool of pages.
>
> If we would start out with an uncacheable region flagged as such, gfp
> can return uncacheable pages just like it can return DMA-able pages.
>
> The number of different "classes" of memory is growing rapidly. I am
> suggesting to take a look at GFP, to see if it can be generalized to
> the point where it can be useful for multiple DMA-capable ranged. Alan
> says that there is a 27-bit limit for a certain sound-card. Sure.
> There is a 32bit limit for many PCI cards. etc.
>
> Alan suggests that we wait until we really hit the wall. I'm saying
> I'd prefer to start looking for (general) solutions now (*).
>
> Once gfp handles multiple, overlapping types of memory, it can easily
> handle the pre-allocated uncacheable pages.

you may consider this to be "scope creep," but page coloring is often
implemented by adding new classes of pages to the system page allocator,
and would be nice to consider in a new implementation of gfp.

- Chuck Lever
--
corporate: <chuckl@netscape.com>
personal: <chucklever@netscape.net> or <cel@monkey.org>

The Linux Scalability project:
http://www.citi.umich.edu/projects/linux-scalability/


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