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SubjectRe: mm and DMA devices


On Thu, 21 Oct 1999, Dan Hollis wrote:

> On Thu, 21 Oct 1999 kernel@kvack.org wrote:
> > memory lists (say 1 per bit of significance above 24 bits). Practically,
> > I have to ask what the value in this is. Do you really need to allocate >
> > 16 MB in the normal use of a bloody sound card?
>
> No, but you have to make sure memory below 16mb is available :}
>
> Or even for many PCI cards, below 1gb or 2gb.
>
> Itd be *very* embarassing to have 4gb of ram, 2gb used, and not be able to
> use your PCI soundcard because it cant allocate ram below 1gb.

Do the math. Right now, GFP_DMA memory is the last part of system memory
to be allocated from. Unless GFP_ATOMIC allocations consume all of the
freepages.min memory reserve (which, for starters, is unlikely -- plus
GFP_ATOMIC allocations are typically short term allocations for network
buffers), you will be able to get GFP_DMA memory. That's the entire
point of the changes made to the allocator. They may have been subtle,
but their impact should be enourmously positive.

-ben


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