[PATCH] mm/vmstat: add header line to /proc/buddyinfo output

[Ye Liu <ye.liu@linux.dev>]

From: Ye Liu <liuye@kylinos.cn>

Add a header line to /proc/buddyinfo that shows the order numbers
for better readability and clarity.

Before:
Node 0, zone      DMA      0      0      0      0      0      0      0 ...
Node 0, zone    DMA32      5      8      6      6      7      5      8 ...
Node 0, zone   Normal   1113    351    138     65     38     31     25 ...

After:
Free pages per order       0      1      2      3      4      5      6 ...
Node 0, zone      DMA      0      0      0      0      0      0      0 ...
Node 0, zone    DMA32      5      8      6      6      7      5      8 ...
Node 0, zone   Normal   1113    351    138     65     38     31     25 ...

Signed-off-by: Ye Liu <liuye@kylinos.cn>
---
 mm/vmstat.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/mm/vmstat.c b/mm/vmstat.c
index bb09c032eecf..e9606457ab91 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1574,7 +1574,14 @@ static void frag_show_print(struct seq_file *m, pg_data_t *pgdat,
  */
 static int frag_show(struct seq_file *m, void *arg)
 {
+	int order;
 	pg_data_t *pgdat = (pg_data_t *)arg;
+	/* Print header */
+	seq_printf(m, "%-21s ", "Free pages per order");
+	for (order = 0; order < NR_PAGE_ORDERS; ++order)
+		seq_printf(m, "%6d ", order);
+	seq_putc(m, '\n');
+
 	walk_zones_in_node(m, pgdat, true, false, frag_show_print);
 	return 0;
 }
-- 
2.43.0