Re: Short question about the mmap method

[Steffen Persvold <sp@scali.no>]

Steffen Persvold wrote:
> 
> Another thing, when allocating memory with vmalloc, how can I be sure that the pages I get is
> adressable within 4GB (i.e I wan't to call pci_map_sg on this buffer for my 32bit PCI device without
> having to use bounce buffers ) ? On systems with less that 4GB of physical memory there's no
> problem, but what happens if you have more (lets say an IA64 server with 16GB of RAM) and don't have
> an IOMMU (like alpha and sparc) ?
> 
> I noticed a vmalloc_32 in linux/vmalloc.h (the comment says "32bit PA addressable pages - eg for PCI
> 32bit devices"), but is that one platform independent (I see that it is only using GFP_KERNEL, while
> vmalloc is using GFP_KERNEL | __GFP_HIGHMEM) ? This issue goes for __get_free_pages too I guess.
> 

Hmm, it helps looking back at old threads (which I actually was involved in).

What ever happened to Jens Axboe's "zone_dma32" patch ? Why wasn't it included in the main 2.4.6
kernel tree (seemed like a good idea to me) ?

Regards,
-- 
  Steffen Persvold   | Scalable Linux Systems |   Try out the world's best   
 mailto:sp@scali.no  |  http://www.scali.com  | performing MPI implementation:
Tel: (+47) 2262 8950 |   Olaf Helsets vei 6   |      - ScaMPI 1.12.2 -         
Fax: (+47) 2262 8951 |   N0621 Oslo, NORWAY   | >300MBytes/s and <4uS latency