Re: [PATCH v1 05/18] mm: improve folio_likely_mapped_shared() using the mapcount of large folios

David Hildenbrand
2024-04-19T13:48:46Z

On 19.04.24 15:47, Yin, Fengwei wrote:
>
>
> On 4/19/2024 5:19 PM, David Hildenbrand wrote:
>> On 19.04.24 04:29, Yin, Fengwei wrote:
>>>
>>>
>>> On 4/10/2024 3:22 AM, David Hildenbrand wrote:
>>>> @@ -2200,7 +2200,22 @@ static inline size_t folio_size(struct folio
>>>> *folio)
>>>>     */
>>>>    static inline bool folio_likely_mapped_shared(struct folio *folio)
>>>>    {
>>>> -    return page_mapcount(folio_page(folio, 0)) > 1;
>>>> +    int mapcount = folio_mapcount(folio);
>>>> +
>>>> +    /* Only partially-mappable folios require more care. */
>>>> +    if (!folio_test_large(folio) ||
>>>> unlikely(folio_test_hugetlb(folio)))
>>>> +        return mapcount > 1;
>>> My understanding is that mapcount > folio_nr_pages(folio) can cover
>>> order 0 folio. And also folio_entire_mapcount() can cover hugetlb (I am
>>> not 100% sure for this one).  I am wondering whether we can drop above
>>> two lines? Thanks.
>>
>> folio_entire_mapcount() does not apply to small folios, so we must not
>> call that for small folios.
> Right. I missed this part. Thanks for clarification.

Thanks for the review!

--
Cheers,

David / dhildenb