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

[David S. Miller]

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
[e-mail]