linux-kernel - [PATCH v1 2/2] mm/damon: Add damos

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Message-ID: <44a30f700fdcf4470318ef5cd248ba98c59b77a2.1753794408.git.pyyjason@gmail.com>
Date: Tue, 29 Jul 2025 06:53:30 -0700
From: Yueyang Pan <pyyjason@...il.com>
To: SeongJae Park <sj@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Usama Arif <usamaarif642@...il.com>
Cc: damon@...ts.linux.dev,
	linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	PanJason <pyyjason@...il.com>
Subject: [PATCH v1 2/2] mm/damon: Add damos_stat support for vaddr

From: PanJason <pyyjason@...il.com>

This patch adds support for damos_stat in virtual address space.
It leverages the walk_page_range to walk the page table and gets
the folio from page table. The last folio scanned is stored in
damos->last_applied to prevent double counting.
---
 mm/damon/vaddr.c | 113 ++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 112 insertions(+), 1 deletion(-)

diff --git a/mm/damon/vaddr.c b/mm/damon/vaddr.c
index 87e825349bdf..3e319b51cfd4 100644
--- a/mm/damon/vaddr.c
+++ b/mm/damon/vaddr.c
@@ -890,6 +890,117 @@ static unsigned long damos_va_migrate(struct damon_target *target,
 	return applied * PAGE_SIZE;
 }
 
+struct damos_va_stat_private {
+	struct damos *scheme;
+	unsigned long *sz_filter_passed;
+};
+
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+static int damos_va_stat_pmd_entry(pmd_t *pmd, unsigned long addr,
+		unsigned long next, struct mm_walk *walk)
+{
+	struct damos_va_stat_private *priv = walk->private;
+	struct damos *s = priv->scheme;
+	unsigned long *sz_filter_passed = priv->sz_filter_passed;
+	struct folio *folio;
+	spinlock_t *ptl;
+	pmd_t pmde;
+
+	ptl = pmd_lock(walk->mm, pmd);
+	pmde = pmdp_get(pmd);
+
+	if (!pmd_present(pmde) || !pmd_trans_huge(pmde))
+		goto unlock;
+
+	/* Tell page walk code to not split the PMD */
+	walk->action = ACTION_CONTINUE;
+
+	folio = damon_get_folio(pmd_pfn(pmde));
+	if (!folio)
+		goto unlock;
+
+	if (damon_invalid_damos_folio(folio, s))
+		goto update_last_applied;
+
+	if (!damos_va_filter_out(s, folio, walk->vma, addr, NULL, pmd)){
+		*sz_filter_passed += folio_size(folio);
+	}
+
+	folio_put(folio);
+update_last_applied:
+	s->last_applied = folio;
+unlock:
+	spin_unlock(ptl);
+	return 0;
+}
+#else
+#define damon_va_stat_pmd_entry NULL
+#endif
+
+static int damos_va_stat_pte_entry(pte_t *pte, unsigned long addr,
+		unsigned long next, struct mm_walk *walk)
+{
+	struct damos_va_stat_private *priv = walk->private;
+	struct damos *s = priv->scheme;
+	unsigned long *sz_filter_passed = priv->sz_filter_passed;
+	struct folio *folio;
+	pte_t ptent;
+
+	ptent = ptep_get(pte);
+	if (pte_none(ptent) || !pte_present(ptent))
+		return 0;
+
+	folio = damon_get_folio(pte_pfn(ptent));
+	if (!folio)
+		return 0;
+
+	if (damon_invalid_damos_folio(folio, s))
+		goto update_last_applied;
+
+	if (!damos_va_filter_out(s, folio, walk->vma, addr, pte, NULL)){
+		*sz_filter_passed += folio_size(folio);
+	}
+
+	folio_put(folio);
+
+update_last_applied:
+	s->last_applied = folio;
+	return 0;
+}
+
+static unsigned long damos_va_stat(struct damon_target *target,
+		struct damon_region *r, struct damos *s,
+		unsigned long *sz_filter_passed)
+{
+
+	struct damos_va_stat_private priv;
+	struct mm_struct *mm;
+	struct mm_walk_ops walk_ops = {
+		.pmd_entry = damos_va_stat_pmd_entry,
+		.pte_entry = damos_va_stat_pte_entry,
+		.walk_lock = PGWALK_RDLOCK,
+	};
+
+	priv.scheme = s;
+	priv.sz_filter_passed = sz_filter_passed;
+
+	if (!damon_scheme_has_filter(s)){
+		return 0;
+	}
+
+	mm = damon_get_mm(target);
+	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);
+	mmput(mm);
+	pr_debug("Call va_stat: %lu\n", *sz_filter_passed);
+	return 0;
+
+}
+
 static unsigned long damon_va_apply_scheme(struct damon_ctx *ctx,
 		struct damon_target *t, struct damon_region *r,
 		struct damos *scheme, unsigned long *sz_filter_passed)
@@ -916,7 +1027,7 @@ static unsigned long damon_va_apply_scheme(struct damon_ctx *ctx,
 	case DAMOS_MIGRATE_COLD:
 		return damos_va_migrate(t, r, scheme, sz_filter_passed);
 	case DAMOS_STAT:
-		return 0;
+		return damos_va_stat(t, r, scheme, sz_filter_passed);
 	default:
 		/*
 		 * DAMOS actions that are not yet supported by 'vaddr'.
-- 
2.47.3