mm-support-batched-checking-of-the-young-flag-for-mglru.patch removed from -mm tree
The quilt patch titled
Subject: mm: support batched checking of the young flag for MGLRU
has been removed from the -mm tree. Its filename was
mm-support-batched-checking-of-the-young-flag-for-mglru.patch
This patch was dropped because it was merged into the mm-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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From: Baolin Wang <[email protected]>
Subject: mm: support batched checking of the young flag for MGLRU
Date: Fri, 6 Mar 2026 14:43:41 +0800
Use the batched helper test_and_clear_young_ptes_notify() to check and clear the young flag to improve the performance during large folio reclamation when MGLRU is enabled.
Meanwhile, we can also support batched checking the young and dirty flag when MGLRU walks the mm's pagetable to update the folios' generation counter. Since MGLRU also checks the PTE dirty bit, use folio_pte_batch_flags() with FPB_MERGE_YOUNG_DIRTY set to detect batches of PTEs for a large folio.
Then we can remove the ptep_test_and_clear_young_notify() since it has no users now.
Note that we also update the 'young' counter and 'mm_stats[MM_LEAF_YOUNG]' counter with the batched count in the lru_gen_look_around() and walk_pte_range(). However, the batched operations may inflate these two counters, because in a large folio not all PTEs may have been accessed. (Additionally, tracking how many PTEs have been accessed within a large folio is not very meaningful, since the mm core actually tracks access/dirty on a per-folio basis, not per page). The impact analysis is as follows:
1. The 'mm_stats[MM_LEAF_YOUNG]' counter has no functional impact and is mainly for debugging.
2. The 'young' counter is used to decide whether to place the current PMD entry into the bloom filters by suitable_to_scan() (so that next time we can check whether it has been accessed again), which may set the hash bit in the bloom filters for a PMD entry that hasn't seen much access. However, bloom filters inherently allow some error, so this effect appears negligible.
---
include/linux/mmzone.h | 5 ++-- mm/internal.h | 6 ----- mm/rmap.c | 28 ++++++++++++------------- mm/vmscan.c | 43 +++++++++++++++++++++++++++++---------- 4 files changed, 49 insertions(+), 33 deletions(-)
include/linux/mmzone.h renamed from include/linux/mmzone.h~mm-support-batched-checking-of-the-young-flag-for-mglru +3 -2
@@ -684,7 +684,7 @@ struct lru_gen_memcg {void lru_gen_init_pgdat (struct pglist_data *pgdat);void lru_gen_init_lruvec (struct lruvec *lruvec); -bool lru_gen_look_around (struct page_vma_mapped_walk *pvmw); +bool lru_gen_look_around (struct page_vma_mapped_walk *pvmw,unsigned int nr);void lru_gen_init_memcg (struct mem_cgroup *memcg);void lru_gen_exit_memcg (struct mem_cgroup *memcg);
@@ -703,7 +703,8 @@ static inline void lru_gen_init_lruvec(s { } -static inline bool lru_gen_look_around (struct page_vma_mapped_walk *pvmw) +static inline bool lru_gen_look_around (struct page_vma_mapped_walk *pvmw, +unsigned int nr) {return false; }
mm/internal.h renamed from mm/internal.h~mm-support-batched-checking-of-the-young-flag-for-mglru +0 -6
@@ -1848,10 +1848,4 @@ static inline int pmdp_test_and_clear_yo#endif /* CONFIG_MMU_NOTIFIER */ -static inline int ptep_test_and_clear_young_notify (struct vm_area_struct *vma, -unsigned long addr,pte_t *ptep) -{ -return test_and_clear_young_ptes_notify (vma, addr, ptep,1 ); -} -#endif /* __MM_INTERNAL_H */
mm/rmap.c renamed from mm/rmap.c~mm-support-batched-checking-of-the-young-flag-for-mglru +14 -14
@@ -965,25 +965,20 @@ static bool folio_referenced_one(structreturn false; } +if (pvmw.pte &&folio_test_large (folio)) { +const unsigned long end_addr =pmd_addr_end (address, vma->vm_end); +const unsigned int max_nr = (end_addr - address) >>PAGE_SHIFT ; +pte_t pteval =ptep_get (pvmw.pte); + + nr =folio_pte_batch (folio, pvmw.pte, pteval, max_nr); + } +if (lru_gen_enabled () && pvmw.pte) { -if (lru_gen_look_around (&pvmw)) +if (lru_gen_look_around (&pvmw, nr)) referenced++; }else if (pvmw.pte) { -if (folio_test_large (folio)) { -unsigned long end_addr =pmd_addr_end (address, vma->vm_end); -unsigned int max_nr = (end_addr - address) >>PAGE_SHIFT ; -pte_t pteval =ptep_get (pvmw.pte); - - nr =folio_pte_batch (folio, pvmw.pte, - pteval, max_nr); - } - - ptes += nr;if (clear_flush_young_ptes_notify (vma, address, pvmw.pte, nr)) referenced++; -/* Skip the batched PTEs */ - pvmw.pte += nr -1 ; - pvmw.address += (nr -1 ) *PAGE_SIZE ; }else if (IS_ENABLED (CONFIG_TRANSPARENT_HUGEPAGE )) {if (pmdp_clear_flush_young_notify (vma, address, pvmw.pmd))
@@ -993,6 +988,7 @@ static bool folio_referenced_one(structWARN_ON_ONCE (1 ); } + ptes += nr; pra->mapcount -= nr;/* * If we are sure that we batched the entire folio,
@@ -1002,6 +998,10 @@ static bool folio_referenced_one(structpage_vma_mapped_walk_done (&pvmw);break ; } + +/* Skip the batched PTEs */ + pvmw.pte += nr -1 ; + pvmw.address += (nr -1 ) *PAGE_SIZE ; }if (referenced)
mm/vmscan.c renamed from mm/vmscan.c~mm-support-batched-checking-of-the-young-flag-for-mglru +32 -11
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Patches currently in -mm which might be from [email protected] are
mm-filemap-fix-nr_pages-calculation-overflow-in-filemap_map_pages.patch mm-vmscan-fix-dirty-folios-throttling-on-cgroup-v1-for-mglru.patch