Re: 32-bit dma allocations on 64-bit platforms

David Mosberger
2004-06-26T05:02:54Z

Terence,

>>>>> On Wed, 23 Jun 2004 13:35:35 -0500, Terence Ripperda <tripperda@nvidia.com> said:

Terence> based on each architecture's paging_init routines, the
Terence> zones look like this:

Terence> x86: ia64: x86_64:
Terence> ZONE_DMA: < 16M < ~4G < 16M
Terence> ZONE_NORMAL: 16M - ~1G > ~4G > 16M
Terence> ZONE_HIMEM: 1G+

Not that it matters here, but for correctness let me note that the
ia64 column is correct only for machines which don't have an I/O MMU.
With I/O MMU, ZONE_DMA will have the same coverage as ZONE_NORMAL with
a recent enough kernel (older kernels had a bug which limited ZONE_DMA
to < 4GB, but that was unintentional).

--david