>> - if (pageout_anon_only_filter && !folio_test_anon(folio))
>> + /* Do not interfere with other mappings of this folio */
>> + if (folio_mapcount(folio) != 1)
>> continue;
>>
>> - VM_BUG_ON_FOLIO(folio_test_large(folio), folio);
>> -
>> - if (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);
>> - }
>> -
>> - /*
>> - * We are deactivating a folio for accelerating reclaiming.
>> - * VM couldn't reclaim the folio unless we clear PG_young.
>> - * As a side effect, it makes confuse idle-page tracking
>> - * because they will miss recent referenced history.
>> - */
>> - folio_clear_referenced(folio);
>> - folio_test_clear_young(folio);
>> - if (folio_test_active(folio))
>> - folio_set_workingset(folio);
>> +pageout_cold_folio:
>> if (pageout) {
>> if (folio_isolate_lru(folio)) {
>> if (folio_test_unevictable(folio))
>> @@ -529,8 +542,30 @@ static int madvise_cold_or_pageout_pte_range(pmd_t *pmd,
>> arch_leave_lazy_mmu_mode();
>> pte_unmap_unlock(start_pte, ptl);
>> }
>> - if (pageout)
>> - reclaim_pages(&folio_list);
>> +
>> + if (pageout) {
>> + LIST_HEAD(reclaim_list);
>> +
>> + while (!list_empty(&folio_list)) {
>> + int refs;
>> + unsigned long flags;
>> + struct mem_cgroup *memcg = folio_memcg(folio);
>> +
>> + folio = lru_to_folio(&folio_list);
>> + list_del(&folio->lru);
>> +
>> + refs = folio_referenced(folio, 0, memcg, &flags);
>> +
>> + if ((flags & VM_LOCKED) || (refs == -1)) {
>> + folio_putback_lru(folio);
>> + continue;
>> + }
>> +
>> + folio_test_clear_referenced(folio);
>> + list_add(&folio->lru, &reclaim_list);
>> + }
>> + reclaim_pages(&reclaim_list);
>> + }
>
> i overlooked the chunk above -- it's unnecessary: after we split the
> large folio (and splice the base folios onto the same LRU list), we
> continue at the position of the first base folio because of:
>
> pte--;
> addr -= PAGE_SIZE;
> continue;
>
> And then we do pte_mkold(), which takes care of the A-bit.
This patch moves the A-bit clear out of the folio isolation loop. So
even the folio is split and loop restarts from the first base folio,
the A-bit is not cleared. A-bit is only cleared in reclaim loop.
There is one option for A-bit clearing:
- clear A-bit of base 4K page in isolation loop and leave large folio
A-bit clearing to reclaim loop.
This patch didn't use it because don't want to introduce A-bit clearing
in two places. But I am open about clearing base 4K page A-bit cleared in
isolation loop. Thanks.
Regards
Yin, Fengwei
