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

From: David S. Miller (davem@redhat.com)
Date: Wed Jul 11 2001 - 18:07:01 EST


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
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