How to guarantee that kmalloc returns an address below 4GB

How to guarantee that kmalloc returns an address below 4GB

[Cestonaro, Thilo (external)]

Hey,

is there an option for kmalloc, which I can use to allocate a buffer which is in physical memory placed below 4GB?
Not in a remapped area.
The only way I found is to use GFP_DMA, but this says the first 16MB isn't it?

Ciao Thilo

Re: How to guarantee that kmalloc returns an address below 4GB

[Stefan Richter]

Cestonaro, Thilo (external) wrote:
> is there an option for kmalloc, which I can use to allocate
> a buffer which is in physical memory placed below 4GB?
> Not in a remapped area.

GFP_DMA32
http://lxr.linux.no/source/include/linux/gfp.h#L82
-- 
Stefan Richter
-=====-=-=== -=-= =----
http://arcgraph.de/sr/

Re: How to guarantee that kmalloc returns an address below 4GB

[Christoph Lameter]

On Wed, 16 May 2007, Stefan Richter wrote:

> Cestonaro, Thilo (external) wrote:
> > is there an option for kmalloc, which I can use to allocate
> > a buffer which is in physical memory placed below 4GB?
> > Not in a remapped area.
> 
> GFP_DMA32

Nope. There are no general slabs available for DMA32.

You could use a dma slab by specifying GFP_DMA. However, on i386 and 
x86_64 this will get you memory in the precious first 16MB. On IA64 and 
other platforms you will get memory < 4GB.

Another option is to use the page allocator and specify GFP_DMA32.