RE: Alloc and lock down large amounts of memory

Roland Kuhn
2002-08-21T13:26:11Z

On Wed, 21 Aug 2002, Mike Galbraith wrote:

> At 03:08 PM 8/20/2002 -0500, Bhavana Nagendra wrote:
> > >
> > > Curiosity: why do you want to do device DMA buffer
> > > allocation from userland?
> >
> >I need 256M memory for a graphics operation. It's a requiremment,
> >can't change it. There will be other reasonably sized allocs in kernel
> >space, this is a special case that will be done from userland. As
> >discussed earlier in this thread, there's no good way of alloc()ing
> >and pinning that much in DMA memory space, is there?
>
> Not that I know of. It seems to me that any interface that tried
> to provide this would have to know what kind of device is going
> to DMA from/to that ram.
>
> Usually, when someone needs a large gob of contiguous ram,
> folks suggest doing the allocation in kernel, and early.
>
BTW: What is the limit for pci_alloc_consistent and friends? Can it really
provide 256MB?

Ciao,
Roland

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