Re: [PATCH v3 2/3] mm/numa: no task_numa_fault() call if PMD is changed

[David Hildenbrand <david@redhat.com>]

On 09.08.24 16:59, Zi Yan wrote:
> When handling a numa page fault, task_numa_fault() should be called by a
> process that restores the page table of the faulted folio to avoid
> duplicated stats counting. Commit c5b5a3dd2c1f ("mm: thp: refactor NUMA
> fault handling") restructured do_huge_pmd_numa_page() and did not avoid
> task_numa_fault() call in the second page table check after a numa
> migration failure. Fix it by making all !pmd_same() return immediately.
> 
> This issue can cause task_numa_fault() being called more than necessary
> and lead to unexpected numa balancing results (It is hard to tell whether
> the issue will cause positive or negative performance impact due to
> duplicated numa fault counting).
> 
> Reported-by: "Huang, Ying" <ying.huang@intel.com>
> Closes: https://lore.kernel.org/linux-mm/87zfqfw0yw.fsf@yhuang6-desk2.ccr.corp.intel.com/
> Fixes: c5b5a3dd2c1f ("mm: thp: refactor NUMA fault handling")
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Zi Yan <ziy@nvidia.com>
> ---

Acked-by: David Hildenbrand <david@redhat.com>

-- 
Cheers,

David / dhildenb