Re: Kernel virtual memory?

Rauli Ruohonen (
Thu, 7 Aug 1997 22:37:37 +0300

>> 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 memory management is done in the CPU, so only the CPU sees
>this virtual address. PCI-BUS- and ISA-Address is on intel architecture
>the same address like the physical address.

Yes, but I didn't mean that kernel should try to use physically fragmented /
above 16MB block for DMA; I meant that the kernel should move non-DMA blocks
away from the "DMA-buffer space"..

>> 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?

Duct tape is like the force.  It has a light side, and a dark side, and
it holds the universe together ...
                -- Carl Zwanzig