linux-kernel - [PATCH v1] mm: vmstat: output reserved_highatomic and free

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Message-ID: <20251027141818.283587-1-jiayuan.chen@linux.dev>
Date: Mon, 27 Oct 2025 22:18:17 +0800
From: Jiayuan Chen <jiayuan.chen@...ux.dev>
To: linux-mm@...ck.org
Cc: Jiayuan Chen <jiayuan.chen@...ux.dev>,
	Andrew Morton <akpm@...ux-foundation.org>,
	David Hildenbrand <david@...hat.com>,
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
	"Liam R. Howlett" <Liam.Howlett@...cle.com>,
	Vlastimil Babka <vbabka@...e.cz>,
	Mike Rapoport <rppt@...nel.org>,
	Suren Baghdasaryan <surenb@...gle.com>,
	Michal Hocko <mhocko@...e.com>,
	linux-kernel@...r.kernel.org
Subject: [PATCH v1] mm: vmstat: output reserved_highatomic and free_highatomic in zoneinfo

The nr_free_highatomic is a key factor in calculating watermarks as it
affects the free pages count. Adding this metric, along with
nr_reserved_highatomic, to /proc/zoneinfo facilitates easier diagnosis
memory watermark calculations and memory pressure states.

Sample output:
cat /proc/zoneinfo
......
pagesets
cpu: 0
		  count:    52069
		  high:     52675
		  batch:    63
		  high_min: 13971
		  high_max: 62284
vm stats threshold: 10
node_unreclaimable:  0
start_pfn:           4096
reserved_highatomic: 5120
free_highatomic:     2081

Signed-off-by: Jiayuan Chen <jiayuan.chen@...ux.dev>
---
 mm/vmstat.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/mm/vmstat.c b/mm/vmstat.c
index f226942db746..b53b07aa29e8 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1852,9 +1852,13 @@ static void zoneinfo_show_print(struct seq_file *m, pg_data_t *pgdat,
 	}
 	seq_printf(m,
 		   "\n  node_unreclaimable:  %u"
-		   "\n  start_pfn:           %lu",
+		   "\n  start_pfn:           %lu"
+		   "\n  reserved_highatomic: %lu"
+		   "\n  free_highatomic:     %lu",
 		   atomic_read(&pgdat->kswapd_failures) >= MAX_RECLAIM_RETRIES,
-		   zone->zone_start_pfn);
+		   zone->zone_start_pfn,
+		   zone->nr_reserved_highatomic,
+		   zone->nr_free_highatomic);
 	seq_putc(m, '\n');
 }
 
-- 
2.43.0