Re: [PATCH v4 4/5] mm: make processing of movable_node arch-specific

[Reza Arbab]

On Tue, Oct 25, 2016 at 11:15:40PM +1100, Balbir Singh wrote:
> After the ack, I realized there were some more checks needed, IOW
> questions for you :)

Hey! No takebacks!

The short answer is that neither of these is a concern.

Longer; if you use "movable_node", x86 can identify these nodes at boot. 
They call memblock_mark_hotplug() while parsing the SRAT. Then, when the 
zones are initialized, those markings are used to determine ZONE_MOVABLE.

We have no analog of this SRAT information, so our movable nodes can 
only be created post boot, by hotplugging and explicitly onlining with 
online_movable.

> 1. Have you checked to see if our memblock allocations spill
> over to probably hotpluggable nodes?

Since our nodes don't exist at boot, we don't have that short window 
before the zones are drawn where the node has normal memory, and a 
kernel allocation might occur within.

> 2. Shouldn't we be marking nodes discovered as movable via
> memblock_mark_hotplug()?

Again, this early boot marking mechanism only applies to movable_node.

--
Reza Arbab