linux-kernel - [PATCH] mm/cma: print total and used pages in cma

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Message-Id: <20250816042842.3959315-1-gxxa03070307@gmail.com>
Date: Sat, 16 Aug 2025 12:28:42 +0800
From: Xiang Gao <gxxa03070307@...il.com>
To: akpm@...ux-foundation.org,
	david@...hat.com
Cc: lorenzo.stoakes@...cle.com,
	Liam.Howlett@...cle.com,
	vbabka@...e.cz,
	rppt@...nel.org,
	surenb@...gle.com,
	mhocko@...e.com,
	linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	gaoxiang17 <gaoxiang17@...omi.com>
Subject: [PATCH] mm/cma: print total and used pages in cma_alloc()

From: gaoxiang17 <gaoxiang17@...omi.com>

This makes cma info more intuitive during debugging.

before:
[   24.407814] cma: cma_alloc(cma (____ptrval____), name: reserved, count 1, align 0)
[   24.413397] cma: cma_alloc(cma (____ptrval____), name: reserved, count 1, align 0)
[   24.415886] cma: cma_alloc(cma (____ptrval____), name: reserved, count 1, align 0)

after:
[   24.069738] cma: cma_alloc(cma (____ptrval____), name: reserved, total pages: 16384, used pages: 64, request pages: 1, align 0)
[   24.075317] cma: cma_alloc(cma (____ptrval____), name: reserved, total pages: 16384, used pages: 65, request pages: 1, align 0)
[   24.078455] cma: cma_alloc(cma (____ptrval____), name: reserved, total pages: 16384, used pages: 66, request pages: 1, align 0)

Signed-off-by: gaoxiang17 <gaoxiang17@...omi.com>
---
 mm/cma.c | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/mm/cma.c b/mm/cma.c
index 2ffa4befb99a..46cc98e7f587 100644
--- a/mm/cma.c
+++ b/mm/cma.c
@@ -776,6 +776,17 @@ static void cma_debug_show_areas(struct cma *cma)
 	spin_unlock_irq(&cma->lock);
 }
 
+static unsigned long cma_get_used_pages(struct cma *cma)
+{
+	unsigned long used;
+
+	spin_lock_irq(&cma->lock);
+	used = bitmap_weight(cma->bitmap, (int)cma_bitmap_maxno(cma));
+	spin_unlock_irq(&cma->lock);
+
+	return used << cma->order_per_bit;
+}
+
 static int cma_range_alloc(struct cma *cma, struct cma_memrange *cmr,
 				unsigned long count, unsigned int align,
 				struct page **pagep, gfp_t gfp)
@@ -858,8 +869,8 @@ static struct page *__cma_alloc(struct cma *cma, unsigned long count,
 	if (!cma || !cma->count)
 		return page;
 
-	pr_debug("%s(cma %p, name: %s, count %lu, align %d)\n", __func__,
-		(void *)cma, cma->name, count, align);
+	pr_debug("%s(cma %p, name: %s, total pages: %lu, used pages: %lu, request pages: %lu, align %d)\n",
+		__func__, (void *)cma, cma->name, cma->count, cma_get_used_pages(cma), count, align);
 
 	if (!count)
 		return page;
-- 
2.34.1