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SubjectRe: Kernel virtual memory?
In article <Pine.LNX.3.96.970808101142.607A-100000@gytha.demon.co.uk>,
Bryn Paul Arnold Jones wrote:

>1. Use the CPU VM hardware to make a virtual address physically be <16M
> (but there's no real point, except to make a bounce buffer that doesn't
> cost any coping).

Hmm? Sounds funny :)

>2. Use the CPU VM hardware to make several virtual ranges be the same
> physical one (Please no one talk about this).

Urgh, I can't think any use for that..

>3. Move a chunk of memory from <16M, and use the VM hardware to make it
> appear unmoved so you need not find/fix all references to it.
>
>I'm assuming 3 as 1 is only helpful in one case (I can think of), and 2
>is generally unhelpful IMHO.

Yep, the #3 is what I meant. And additionally you could make fragmented
memory look like linear, so kmalloc(big_amount) would always work if there's
"big_amount" of memory available, no matter how fragmented it is.

>You could then have something like this happening:
>
>buf=kmalloc(some_memory, GFP_BUFFER);
>make_dmaable(buf, some_memory);

I thought more of something like buf=kmalloc(some_memory,GFP_DMA);

--
Real Users are afraid they'll break the machine -- but they're never
afraid to break your face.

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