Re: [PATCH v4 6/6] mm: madvise: Avoid split during MADV_PAGEOUT and MADV_COLD

David Hildenbrand
2024-03-20T14:09:20Z

On 20.03.24 14:57, Ryan Roberts wrote:
> On 15/03/2024 10:35, David Hildenbrand wrote:
>>> -        if (!pageout && pte_young(ptent)) {
>>> -            ptent = ptep_get_and_clear_full(mm, addr, pte,
>>> -                            tlb->fullmm);
>>> -            ptent = pte_mkold(ptent);
>>> -            set_pte_at(mm, addr, pte, ptent);
>>> -            tlb_remove_tlb_entry(tlb, pte, addr);
>>> +        if (!pageout) {
>>> +            for (; nr != 0; nr--, pte++, addr += PAGE_SIZE) {
>>> +                if (ptep_test_and_clear_young(vma, addr, pte))
>>> +                    tlb_remove_tlb_entry(tlb, pte, addr);
>>> +            }
>>>           }
>>
>>
>> The following might turn out a bit nicer: Make folio_pte_batch() collect
>> "any_young", then doing something like we do with "any_writable" in the fork()
>> case:
>>
>> ...
>>     nr = folio_pte_batch(folio, addr, pte, ptent, max_nr,
>>                  fpb_flags, NULL, any_young);
>>     if (any_young)
>>         pte_mkyoung(ptent)
>> ...
>>
>> if (!pageout && pte_young(ptent)) {
>>     mkold_full_ptes(mm, addr, pte, nr, tlb->fullmm);
>
> I don't think tlb->fullmm makes sense here because we are not clearing the pte,
> so there is no chance of optimization? So planning to call this mkold_ptes() and
> remove that param. Have I missed something?

Agreed.

--
Cheers,

David / dhildenb