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

[Gregory Price <gourry@gourry.net>]

On Thu, Jul 09, 2026 at 07:09:29PM +0800, Huang, Ying wrote:
> Gregory Price <gourry@gourry.net> 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. 

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).

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.

~Gregory