Re: swiotlb detection should be memory hotplug aware ?

[FUJITA Tomonori]

On Wed, 28 Jul 2010 13:09:57 +0200
Andi Kleen <andi@xxxxxxxxxxxxxx> wrote:

> FUJITA Tomonori <fujita.tomonori@xxxxxxxxxxxxx> writes:
> >
> >> The other problem is that using only  two bits for the needed address 
> >> space is also extremly
> >> inefficient (4GB and 16MB on x86). Really want masks everywhere and 
> >> optimize for the
> >> actual requirements.
> >
> > swiotlb doesn't allocate GFP_DMA memory. It handles only GFP_DMA32.
> 
> I was lumping GFP_DMA and swiotlb together here. The
> pci_alloc_consistent() function uses both interchangedly.
> They really effectively are the same thing these days
> and just separated by historical accident.

Sorry, I meant to ZONE_DMA.

You are talking about your dma mask allocation patchset, right?

I meant that swiotlb doesn't need to handle ZONE_DMA. It handles only
devices that can handle ZONE_DMA32.


> > I have a half-baked patch for it. I'll send it later.
> 
> The problem are still the *_map users which usually cannot sleep,
> and then it's difficult to grow.

Why we can't use GFP_NOWAIT?

My approach is starting with small (like 4MB) and increasing io_tbl by
chunk such as 4MB.
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