From 4a34c584d8cd13d2b721d21cf629f77c60bfb4a4 Mon Sep 17 00:00:00 2001 From: Dev Jain Date: Wed, 16 Apr 2025 11:00:48 +0530 Subject: [PATCH] mempolicy: optimize queue_folios_pte_range by PTE batching After the check for queue_folio_required(), the code only cares about the folio in the for loop, i.e the PTEs are redundant. Therefore, optimize this loop by skipping over a PTE batch mapping the same folio. With a test program migrating pages of the calling process, which includes a mapped VMA of size 4GB with pte-mapped large folios of order-9, and migrating once back and forth node-0 and node-1, the average execution time reduces from 7.5 to 4 seconds, giving an approx 47% speedup. Link: https://lkml.kernel.org/r/20250416053048.96479-1-dev.jain@arm.com Signed-off-by: Dev Jain Acked-by: David Hildenbrand Cc: Baolin Wang Cc: Hugh Dickins Cc: Matthew Wilcox (Oracle) Cc: Ryan Roberts Cc: Vishal Moola (Oracle) Cc: Yang Shi Cc: Zi Yan Signed-off-by: Andrew Morton --- mm/mempolicy.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/mm/mempolicy.c b/mm/mempolicy.c index b28a1e6ae0964..4d2dc8b639659 100644 --- a/mm/mempolicy.c +++ b/mm/mempolicy.c @@ -566,6 +566,7 @@ static void queue_folios_pmd(pmd_t *pmd, struct mm_walk *walk) static int queue_folios_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, struct mm_walk *walk) { + const fpb_t fpb_flags = FPB_IGNORE_DIRTY | FPB_IGNORE_SOFT_DIRTY; struct vm_area_struct *vma = walk->vma; struct folio *folio; struct queue_pages *qp = walk->private; @@ -573,6 +574,7 @@ static int queue_folios_pte_range(pmd_t *pmd, unsigned long addr, pte_t *pte, *mapped_pte; pte_t ptent; spinlock_t *ptl; + int max_nr, nr; ptl = pmd_trans_huge_lock(pmd, vma); if (ptl) { @@ -586,7 +588,9 @@ static int queue_folios_pte_range(pmd_t *pmd, unsigned long addr, walk->action = ACTION_AGAIN; return 0; } - for (; addr != end; pte++, addr += PAGE_SIZE) { + for (; addr != end; pte += nr, addr += nr * PAGE_SIZE) { + max_nr = (end - addr) >> PAGE_SHIFT; + nr = 1; ptent = ptep_get(pte); if (pte_none(ptent)) continue; @@ -598,6 +602,10 @@ static int queue_folios_pte_range(pmd_t *pmd, unsigned long addr, folio = vm_normal_folio(vma, addr, ptent); if (!folio || folio_is_zone_device(folio)) continue; + if (folio_test_large(folio) && max_nr != 1) + nr = folio_pte_batch(folio, addr, pte, ptent, + max_nr, fpb_flags, + NULL, NULL, NULL); /* * vm_normal_folio() filters out zero pages, but there might * still be reserved folios to skip, perhaps in a VDSO. @@ -630,7 +638,7 @@ static int queue_folios_pte_range(pmd_t *pmd, unsigned long addr, if (!(flags & (MPOL_MF_MOVE | MPOL_MF_MOVE_ALL)) || !vma_migratable(vma) || !migrate_folio_add(folio, qp->pagelist, flags)) { - qp->nr_failed++; + qp->nr_failed += nr; if (strictly_unmovable(flags)) break; } -- 2.39.5