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
