linux-kernel - Re: [PATCH] mm/vmstat: add header line to /proc/buddyinfo output

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Message-ID: <aMu01xIkj-3hgW88@tiehlicka>
Date: Thu, 18 Sep 2025 09:29:27 +0200
From: Michal Hocko <mhocko@...e.com>
To: Ye Liu <ye.liu@...ux.dev>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
	David Hildenbrand <david@...hat.com>, Ye Liu <liuye@...inos.cn>,
	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>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/vmstat: add header line to /proc/buddyinfo output

On Thu 18-09-25 15:17:40, Ye Liu wrote:
> From: Ye Liu <liuye@...inos.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 ...

Why is this needed? And have you considered tha this might break
existing parsers of the file?

> 
> Signed-off-by: Ye Liu <liuye@...inos.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
> 

-- 
Michal Hocko
SUSE Labs