Re: (reposting) how to get DMA'able memory within 4GB on 64-bit m

David S. Miller
2001-07-11T23:07:26Z

Jes Sorensen writes:
> The overhead is going be negligeble, the overhead of highmem itself is
> much worse.

Once Jens's block layer stuff goes in, a lot of that overhead simply
disappears since the page cache need not bounce buffers. The
networking can already technically cope with this too.

> Not to mention that today some dma_addr_t's might not be
> packed properly in data structure hence they ending up taking 8 bytes
> anyway.

Not on x86 which is the current main benefactor of highmem.

Later,
David S. Miller
davem@redhat.com