Re: [PATCH 0/2] mm: don't apply task mempolicy to unmovable kernel allocations

[Huang, Ying]

Gregory Price <gourry@xxxxxxxxxx> writes:

> On Thu, Jul 09, 2026 at 07:09:29PM +0800, Huang, Ying wrote:
>> Gregory Price <gourry@xxxxxxxxxx> writes:
>> 
>> > The unmovable unaccounted kernel allocations stop following the
>> > task policy and place node-local. With no policy set, both place
>> > node-local as before.
>> 
>> Personally, I think this should be the right thing to do theoretically.
>> However, you may need to find some practical issues that this resolves.
>> 
>
> I don't entirely disagree, but there is at least one scenario where this
> is an obvious improvement:
>
>   BIOS-configured CXL memory brought up in ZONE_NORMAL. 

Per my understanding, kernel configured CXL memory can be in ZONE_NORMAL
and BIOS-configured one can be in ZONE_MOVABLE.  Right?

> An task interleave policy on such a system will end up with unaccounted
> kernel allocations landing on the remote node, which is just not
> preferable at all (and uncorrectable).

Anyway, some number will be good IMHO.

> It's not a complete fix (fallbacks can still occur under pressure), but
> it's one piece of the puzzle.
>
> Forward looking:  This patch makes private-node's with ZONE_NORMAL
> reliably hot-un-pluggable.  But that improvement is obviously predicated
> on work that isn't upstream (yet :] ).
>
> I need to send a v2 of this with SLAB_ACCOUNT fixed up, and some numbers
> to justify dropping the pagecache fix.  But I will probably sandbag this
> a bit until i finally send out v5 of private nodes.

---
Best Regards,
Huang, Ying