Re: [PATCH 00/22] Don't use kmalloc() with GFP_DMA

Christoph Hellwig
2022-02-24T06:33:37Z

On Wed, Feb 23, 2022 at 08:18:08PM +0100, Heiko Carstens wrote:
> > The long term goal is to remove ZONE_DMA entirely at least for
> > architectures that only use the small 16MB ISA-style one. It can
> > then be replaced with for example a CMA area and fall into a movable
> > zone. I'd have to prototype this first and see how it applies to the
> > s390 case. It might not be worth it and maybe we should replace
> > ZONE_DMA and ZONE_DMA32 with a ZONE_LIMITED for those use cases as
> > the amount covered tends to not be totally out of line for what we
> > built the zone infrastructure.
>
> So probably I'm missing something; but for small systems where we
> would only have ZONE_DMA, how would a CMA area within this zone
> improve things?

It would not, but more importantly we would not need it at all. The
thinking here is really about the nasty 16MB ISA-style zone DMA.
a 31-bit something rather different.