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SubjectRe: Kernel virtual memory?
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On Thu, 7 Aug 1997, Rauli Ruohonen wrote:

> Could kernel use virtual memory hardware to make non-linear chunks of
> memory to look linear? It seems to me that it could solve the problems
> with memory fragmentation and DMA memory allocation.
>
> DMA memory could be allocated by moving allocated blocks away from the
> lower 16MB, and other parts of kernel could be made happy by changing the
> page tables accordingly.
>
> So, is this possible/feasible/too ugly to implement?
>

Erm DMA stands for direct memory access, the CPU doesn't get a look-in
(past seting it all up), and so can't mess about (that's the advantage,
the CPU isn't tied up). The DMAing is actually done by whatever card is
transferring the data, and so it's talking to physical memory using
physical addresses.

Bryn
PS Some hardware may be overseeing, but I don't think so.
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