Skip to contentSkip to conversation

mm-damon-vaddr-attempt-per-vma-lock-during-page-table-walk.patch removed from -mm tree

merged mm-stable Andrew Morton 1 participant 1 message Jun 2

lore
Share & tools
lore

Andrew Morton

author tree notice Applied
#0 lore raw

The quilt patch titled
Subject: mm/damon/vaddr: attempt per-vma lock during page table walk
has been removed from the -mm tree. Its filename was
mm-damon-vaddr-attempt-per-vma-lock-during-page-table-walk.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

------------------------------------------------------
From: Kefeng Wang <[email protected]>
Subject: mm/damon/vaddr: attempt per-vma lock during page table walk
Date: Tue, 12 May 2026 23:15:23 +0800

Currently, DAMON virtual address operations use mmap_read_lock during page table walks, which can cause unnecessary contention under high concurrency.

Introduce damon_va_walk_page_range() to first attempt acquiring a per-vma lock. If the VMA is found and the range is fully contained within it, the page table walk proceeds with the per-vma lock instead of mmap_read_lock.

This optimization is expected to be particularly effective for damon_va_young() and damon_va_mkold(), which are frequently called and typically operate within a single VMA.

Link https://lore.kernel.org/[email protected] open here
Signed-off-by Kefeng Wang <[email protected]>
Reviewed-by SeongJae Park <[email protected]>
Cc Nanyong Sun <[email protected]>
Signed-off-by Andrew Morton <[email protected]>

---

 mm/damon/vaddr.c |   69 ++++++++++++++++++++++++++++-----------------
 1 file changed, 43 insertions(+), 26 deletions(-)
mm/damon/vaddr.c renamed from mm/damon/vaddr.c~mm-damon-vaddr-attempt-per-vma-lock-during-page-table-walk +43 -26
@@ -237,6 +237,35 @@ static void damon_va_update(struct damon
 	}
 }
 
+static void damon_va_walk_page_range(struct mm_struct *mm, unsigned long start,
+		unsigned long end, struct mm_walk_ops *ops, void *private)
+{
+	struct vm_area_struct *vma;
+
+	vma = lock_vma_under_rcu(mm, start);
+	if (!vma)
+		goto lock_mmap;
+
+	if (end > vma->vm_end) {
+		vma_end_read(vma);
+		goto lock_mmap;
+	}
+
+	if (!(vma->vm_flags & VM_PFNMAP)) {
+		ops->walk_lock = PGWALK_VMA_RDLOCK_VERIFY;
+		walk_page_range_vma(vma, start, end, ops, private);
+	}
+
+	vma_end_read(vma);
+	return;
+
+lock_mmap:
+	mmap_read_lock(mm);
+	ops->walk_lock = PGWALK_RDLOCK;
+	walk_page_range(mm, start, end, ops, private);
+	mmap_read_unlock(mm);
+}
+
 static int damon_mkold_pmd_entry(pmd_t *pmd, unsigned long addr,
 		unsigned long next, struct mm_walk *walk)
 {

@@ -315,17 +344,14 @@ out:
 #define damon_mkold_hugetlb_entry NULL
 #endif /* CONFIG_HUGETLB_PAGE */
 
-static const struct mm_walk_ops damon_mkold_ops = {
-	.pmd_entry = damon_mkold_pmd_entry,
-	.hugetlb_entry = damon_mkold_hugetlb_entry,
-	.walk_lock = PGWALK_RDLOCK,
-};
-
 static void damon_va_mkold(struct mm_struct *mm, unsigned long addr)
 {
-	mmap_read_lock(mm);
-	walk_page_range(mm, addr, addr + 1, &damon_mkold_ops, NULL);
-	mmap_read_unlock(mm);
+	struct mm_walk_ops damon_mkold_ops = {
+		.pmd_entry = damon_mkold_pmd_entry,
+		.hugetlb_entry = damon_mkold_hugetlb_entry,
+	};
+
+	damon_va_walk_page_range(mm, addr, addr + 1, &damon_mkold_ops, NULL);
 }
 
 /*

@@ -445,12 +471,6 @@ out:
 #define damon_young_hugetlb_entry NULL
 #endif /* CONFIG_HUGETLB_PAGE */
 
-static const struct mm_walk_ops damon_young_ops = {
-	.pmd_entry = damon_young_pmd_entry,
-	.hugetlb_entry = damon_young_hugetlb_entry,
-	.walk_lock = PGWALK_RDLOCK,
-};
-
 static bool damon_va_young(struct mm_struct *mm, unsigned long addr,
 		unsigned long *folio_sz)
 {

@@ -459,9 +479,12 @@ static bool damon_va_young(struct mm_str
 		.young = false,
 	};
 
-	mmap_read_lock(mm);
-	walk_page_range(mm, addr, addr + 1, &damon_young_ops, &arg);
-	mmap_read_unlock(mm);
+	struct mm_walk_ops damon_young_ops = {
+		.pmd_entry = damon_young_pmd_entry,
+		.hugetlb_entry = damon_young_hugetlb_entry,
+	};
+
+	damon_va_walk_page_range(mm, addr, addr + 1, &damon_young_ops, &arg);
 	return arg.young;
 }
 

@@ -750,7 +773,6 @@ static unsigned long damos_va_migrate(st
 	struct mm_walk_ops walk_ops = {
 		.pmd_entry = damos_va_migrate_pmd_entry,
 		.pte_entry = NULL,
-		.walk_lock = PGWALK_RDLOCK,
 	};
 
 	use_target_nid = dests->nr_dests == 0;

@@ -768,9 +790,7 @@ static unsigned long damos_va_migrate(st
 	if (!mm)
 		goto free_lists;
 
-	mmap_read_lock(mm);
-	walk_page_range(mm, r->ar.start, r->ar.end, &walk_ops, &priv);
-	mmap_read_unlock(mm);
+	damon_va_walk_page_range(mm, r->ar.start, r->ar.end, &walk_ops, &priv);
 	mmput(mm);
 
 	for (int i = 0; i < nr_dests; i++) {

@@ -862,7 +882,6 @@ static unsigned long damos_va_stat(struc
 	struct mm_struct *mm;
 	struct mm_walk_ops walk_ops = {
 		.pmd_entry = damos_va_stat_pmd_entry,
-		.walk_lock = PGWALK_RDLOCK,
 	};
 
 	priv.scheme = s;

@@ -875,9 +894,7 @@ static unsigned long damos_va_stat(struc
 	if (!mm)
 		return 0;
 
-	mmap_read_lock(mm);
-	walk_page_range(mm, r->ar.start, r->ar.end, &walk_ops, &priv);
-	mmap_read_unlock(mm);
+	damon_va_walk_page_range(mm, r->ar.start, r->ar.end, &walk_ops, &priv);
 	mmput(mm);
 	return 0;
 }

_

Patches currently in -mm which might be from [email protected] are