Re: [PATCH] mm/numa_balancing: allow migrate on protnone reference with MPOL_WEIGHTED_INTERLEAVE policy

[Gregory Price <gourry@gourry.net>]

On Thu, Oct 01, 2026 at 12:54:22PM +0200, David Hildenbrand (Arm) wrote:
> > If this is a initial-fill problem, can userspace set weighted interleave
> > initially? The program or harness can observe memory usage of the program
> > or related NUMA nodes and switch the policy to numa balancing via
> > set_mempolicy() or mbind() without MPOL_MF_MOVE after certain threshold
> > is met?
> 
> You mean: use the weighted policy initially and then switch to a NUMA-balancing
> one which doesn't involve the weights anymore?
> 
> That makes more sense to me. Although I struggle to see why an effectively
> "let's put random memory on slow and others at hot" is a good starting point to
> later let if be fixed up by actual balancing/tiering.
> 
> It all sounds a bit hackish. :)
>

It is a bit of a non-combo (Nonbo).  You're using weighted interleave
with the intent of spreading out the bandwidth utilization (and maybe to
offset some reclaim behavior? *shrug*) but then undo all the placement
with tiering.

But, in defense of the hackery - I have seen strategies like this work
to optimize startup times and then let tiering optimize runtime.  Phased
execution gets funky like that.

~Gregory