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

[Li Zhe]

On 9/30/26 4:43 PM, Gregory Price wrote:
> On Wed, Sep 30, 2026 at 03:26:17PM +0800, Li Zhe wrote:
>> Allow MPOL_F_NUMA_BALANCING for MPOL_WEIGHTED_INTERLEAVE.  As with
>> MPOL_BIND and MPOL_PREFERRED_MANY, keep migration constrained by the
>> policy nodemask: if the CPU's node is outside the nodemask, do not
>> migrate the folio there.
>>
> Why for WEIGHTED_INTERLEAVE and not INTERLEAVE as well?


Thanks for pointing this out.

I focused on MPOL_WEIGHTED_INTERLEAVE in v1 because the motivating use
case is to seed memory across tiers with a configurable ratio at
allocation time, and then let NUMA balancing/memory tiering adjust the
placement based on access patterns. With equal weights,
MPOL_WEIGHTED_INTERLEAVE can also cover the regular interleave
allocation pattern.

That said, I agree that MPOL_INTERLEAVE can be handled consistently as
well. Since this is still an explicit opt-in via MPOL_F_NUMA_BALANCING,
unless others see a reason to keep MPOL_INTERLEAVE out, I will extend
this in v2 to cover both MPOL_INTERLEAVE and MPOL_WEIGHTED_INTERLEAVE
with the same nodemask constraint.

Thanks,
Zhe

>
> Otherwise this seems reasonable.
>
> ~Gregory