Re: Page allocator: Single Zone optimizations

Andi Kleen
2006-10-28T16:12:01Z

> It's all pretty simple. But it'd be hacky to implement it in terms of
> "highmem". It would be better if we could just tell the core MM "here's a
> 4G zone" and "here's a 60G zone". The 60G zone is only used for
> GFP_HIGHUSER allocations and is hence unpluggable.
>
> I don't think there's any other (practical) way of implementing hot-unplug.

If it's implemented this way it would be important that the boundaries
between nodes are not fixed, but tunable. Otherwise kernel memory
intensive loads might be suddenly impossible.

>
> But hot-unplug is just an example. My main point here is that it is
> desirable that we get away from the up-to-four magical hard-wired zones in
> core MM.

I mostly agree. At least GFP_DMA needs to go and replaced
with some API that gives memory masks and lets an underlying
allocator figure it out. GFP_DMA32 might still have a better case
though because those are pretty common, but ultimatively
a mask based interface is here much better too.

-Andi