Messages in this thread | | | Date | Fri, 27 Aug 1999 16:41:37 +0200 | From | Benjamin Herrenschmidt <> | Subject | Re: Cache incoherencies |
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On Fri, Aug 27, 1999, Rogier Wolff <R.E.Wolff@BitWizard.nl> wrote:
>I think we should take a step back, abstract the GFP mechansism to the >point where it can satisfy a "gimmy any page" request, which >technically turns into "preferably a page from non-DMA memory, but if >you're out of those, give me a DMA-able page". > >A driver wanting to do DMA will request "a DMA-ABLE page" (with either >the 16M ISA limit, the 1M XT limit, or the 4G PCI limit!), with "if >you're out of those, give up". > >I think that GFP may need to be redesigned one time or another. >However, once that is done, taking along things as "uncached" pages, >should become a breeze. Yes, the current implementation makes it a >quick hack to vmalloc.
I beleive we should not confuse DMA-able and unached. DMA can be perfectly fine on cachable memory on a non-coherent architecture if you do the appropriate flush when needed. Making all DMA memory non-cachable would have a huge performance hit on some platform.
>I think that generalizing gfp is a good idea in the end.
I'll let more competent people handle this and keep my vmalloc stuff for now ;-)
-- Perso. e-mail: <mailto:bh40@calva.net> Work e-mail: <mailto:benh@mipsys.com> BenH. Web : <http://calvaweb.calvacom.fr/bh40/>
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