Re: [PATCH v3 4/5] powerpc/mm: restore top-down allocation when using movable_node

From: Reza Arbab
Date: Tue Oct 04 2016 - 16:23:50 EST

On Tue, Oct 04, 2016 at 11:48:30AM +1100, Balbir Singh wrote:
On 27/09/16 10:14, Reza Arbab wrote:
Right. To be clear, the background info I put in the commit log refers to x86, where the SRAT can describe movable nodes which exist at boot. They're trying to avoid allocations from those nodes before they've been identified.

On power, movable nodes can only exist via hotplug, so that scenario can't happen. We can immediately go back to top-down allocation. That is the missing call being added in the patch.

Can we fix cmdline_parse_movable_node() to do the right thing? I suspect that code is heavily x86 only in the sense that no other arch needs it.

Good idea. We could change it so things only go bottom-up on x86 in the first place.

A nice consequence is that CONFIG_MOVABLE_NODE would then basically be usable on any platform with memory hotplug, not just PPC64 and X86_64.

I'll see if I can move the relevant code into an arch_*() call or otherwise factor it out.

Reza Arbab