Messages in this thread | | | Subject | Re: Kernel virtual memory? | Date | Fri, 8 Aug 1997 00:01:41 +0200 (MET DST) | From | (Rogier Wolff) |
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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.
The problem is that the only thing you can't do (except for on a Sparc (#) ) is solve DMA problems.
> 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.
Yeah. Another part of the kernel might still be having a "physical" pointer to that memory because some other device is going to DMA into that memory.
> So, is this possible/feasible/too ugly to implement?
Yeah. Too ugly.
Roger.
(#) Many sparcs use the SBUS which has "DVMA", Direct Virtual Memory Access: They go through the MMU for DMA accesses.......
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