Re: [PATCH 3/4] Embed zone_id information within the zonelist->zones pointer

Andy Isaacson
2007-08-14T19:43:56Z

On Tue, Aug 14, 2007 at 10:23:51PM +0200, Andi Kleen wrote:
> > bcm43xx hardware does show up on low-end MIPS boxes (wrt54g anybody?)
> > that would be sorely hurt by excess copies.
>
> Lowend boxes don't have more than 1GB of RAM. With <= 1GB you don't
> need to copy on bcm43xx.

OK, that makes sense and is reassuring, but note that some MIPS boxes
have only part of their physical memory below 1GB; IIRC the
BCM4704/BCM5836 supports up to 512MB of physical memory, with 256MB in
the first GB and the second 256MB located above the 1GB line. (But it's
been a while since I've run such a machine, so I could be misremembering
the sizes and offsets.)

Yeah, if you stick a PCI chip with a 30-bit PCI DMA mask into a machine
with memory above 1GB, then copying has to happen. Unless the memory
allocator can avoid returning memory in the un-dma-able region...

-andy