Re: [PATCH v1 1/2] mm/vmscan: balance demotion allocation in alloc_demote_folio()

[Bing Jiao <bingjiao@google.com>]

On Thu, Jan 08, 2026 at 06:14:02PM +0530, Donet Tom wrote:
>
> On 1/7/26 12:58 PM, Bing Jiao wrote:
> > +	/* Randomly select a node from fallback nodes for balanced allocation */
> > +	if (allowed_mask) {
> > +		mtc->nid = node_random(allowed_mask);
>
>
> This random selection can cause allocations to fall back to distant memory
> even when the nearer demotion target has sufficient free memory, correct?
> Could this also lead to increased promotion latency?

Hi Donet,

Thanks for your questions.

Yes, the random selection could select a distant node and lead to
incresed promotion latency.

I just realized that the the fallback allocation should not weighted
by a single metric, such as node distance, capacity, free space.
We need a thoroughly study before changing alloc_demote_folio().

Best,
Bing