Re: [RFC PATCH] mm: hugetlb: remove __GFP_THISNODE flag when dissolving the old hugetlb

[Baolin Wang]

On 2024/2/5 22:23, Michal Hocko wrote:
> On Mon 05-02-24 21:06:17, Baolin Wang wrote:
> [...]
> > > It is quite possible that traditional users (like large DBs) do not use
> > > CMA heavily so such a problem was not observed so far. That doesn't mean
> > > those problems do not really matter.
> >
> > CMA is just one case, as I mentioned before, other situations can also break
> > the per-node hugetlb pool now.
>
> Is there any other case than memory hotplug which is arguably different
> as it is a disruptive operation already.

Yes, like I said before the longterm pinning, memory failure and the 
users of alloc_contig_pages() may also break the per-node hugetlb pool.

> > Let's focus on the main point, why we should still keep inconsistency
> > behavior to handle free and in-use hugetlb for alloc_contig_range()? That's
> > really confused.
>
> yes, this should behave consistently. And the least surprising way to
> handle that from the user configuration POV is to not move outside of
> the original NUMA node.

So you mean we should also add __GFP_THISNODE flag in 
alloc_migration_target() when allocating a new hugetlb as the target for 
migration, that can unify the behavior and avoid breaking the per-node pool?