[PATCH v4 3/4] mm: Support batched unmap for lazyfree large folios during reclamation
Lance Yang
lance.yang at linux.dev
Wed Jun 25 18:17:33 PDT 2025
On 2025/6/26 05:03, Barry Song wrote:
> On Thu, Jun 26, 2025 at 12:25 AM David Hildenbrand <david at redhat.com> wrote:
>>
>> On 25.06.25 14:20, Lance Yang wrote:
> [...]
>>> Hmm... I have a question about the reference counting here ...
>>>
>>> if (vma->vm_flags & VM_LOCKED)
>>> mlock_drain_local();
>>> folio_put(folio);
>>> /* We have already batched the entire folio */
>>>
>>> Does anyone else still hold a reference to this folio after folio_put()?
>>
>> The caller of the unmap operation should better hold a reference :)
>>
>> Also, I am not sure why we don't perform a
>>
>> folio_put_refs(folio, nr_pages);
>
> Because we've already called folio_ref_sub(folio, nr_pages - 1);
> Looking back, it’s kind of ugly, huh.
>
> discard:
> if (unlikely(folio_test_hugetlb(folio))) {
> hugetlb_remove_rmap(folio);
> } else {
> folio_remove_rmap_ptes(folio, subpage, nr_pages, vma);
> folio_ref_sub(folio, nr_pages - 1);
> }
>
> I assume Lance will send a patch? If so, remember to remove this
> when switching to folio_put_refs(folio, nr_pages);
Ah, got it. Thanks for pointing that out!
More information about the linux-riscv
mailing list