Re: [PATCH v3 3/3] mm/vmscan: don't demote if there is not enough free memory in the lower memory tier

[Gregory Price]

> +	for_each_node_mask(nid, allowed_mask) {
> +		int z;
> +		struct zone *zone;
> +		struct pglist_data *pgdat = NODE_DATA(nid);
> +
> +		for_each_managed_zone_pgdat(zone, pgdat, z, MAX_NR_ZONES - 1) {
> +			if (zone_watermark_ok(zone, 0, min_wmark_pages(zone),
> +						ZONE_MOVABLE, 0))

Why does this only check zone movable?  

Also, would this also limit pressure-signal to invoke reclaim when
there is still swap space available?  Should demotion not be a pressure
source for triggering harder reclaim?

~Gregory