Re: [PATCH v2 0/4] sched/numa: stop VMA scan filters from gating promotion

[Gregory Price]

On Fri, Sep 18, 2026 at 04:56:34PM -0400, Zi Yan wrote:
> >
> > Tested on a host with 768GB/256GB DRAM/CXL.
> > Ran 2 ~430GB database workloads with large (>300GB) shmem VMAs.
> 
> Do you just launch them without any additional NUMA control or NUMA
> policy configuration, like using numactl? Just want to understand the
> scope of the issue and how well the fixes are tested. It might be good
> to have a list of expected behaviors for people/AI to check against.
>

We found these issues while testing fairness controls with Joshua's
tiered memcg limits patches [1].

We were seeing very lopsided bandwidth utilization between tiers.

When dropped all the memcg extensions and tested these patches by
themselves, we found that numa balancing was completely broken -
starting with Johannes' shmem fix [2].

Otherwise - No other numa controls are used on these workloads.
  - no numactl
  - no mbind()/set_mempolicy()
  - no cpuset.mems
  - etc

These fixes impact the fault-injecting side (spraying PROT_NONE),
not the fault-handling side. So mempolicy and cpuset doesn't really
come into the picture.

It's more of an internal-consistency issue for numab itself.

~Gregory

[1] https://lore.kernel.org/all/20260807202059.2620949-1-joshua.hahnjy@xxxxxxxxx/
[2] https://lore.kernel.org/all/20260629163337.1264881-1-hannes@xxxxxxxxxxx/