Re: [PATCH 2/2] mm/memcg: migrate per-node hugetlb lruvec stat together with hugetlb folio

[Joshua Hahn <joshua.hahnjy@gmail.com>]

On Mon, 21 Sep 2026 17:12:35 +0800 Hongfu Li <hongfu.li@linux.dev> wrote:

> From: Hongfu Li <lihongfu@kylinos.cn>
> 
> memory.numa_stat exposes per-node hugetlb counters from per-node lruvec
> stats. These stats are accounted against folio_nid(): incremented on
> the folio's node when handed to a user, decremented when the folio is
> returned to the pool.
> 
> During hugetlb folio migration, mem_cgroup_migrate() moves the charge
> to the new folio and drops the memcg data of the old one, so the free
> of the old folio right after the migration skips the memcg per-node
> lruvec decrement. The hugetlb count stays attributed to the old node
> for the rest of the life of the charge, while the target folio gets no
> increment on the new node; its later free decrements a counter that
> was never incremented.
> 
> Migrate the per-node lruvec accounting alongside migration. Global
> memcg totals remain balanced because they track resource consumption,
> not node placement.

Hi Hongfu,

This is another great catch, thank you for working on the fix!
I was able to confirm that the issue exists and was fixed by this patch.

Tested-by: Joshua Hahn <joshua.hahnjy@gmail.com>
Reviewed-by: Joshua Hahn <joshua.hahnjy@gmail.com>

> Fixes: 05d4532b60e3 ("memcg/hugetlb: add hugeTLB counters to memcg")
> Cc: stable@vger.kernel.org
> Signed-off-by: Hongfu Li <lihongfu@kylinos.cn>