linux-kernel - Re: [PATCH 3/3] mm/vmstat: simplfy extfrag_show_print with fragmentation

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Date: Fri, 15 Mar 2024 12:13:12 +0100
From: Vlastimil Babka <vbabka@...e.cz>
To: Luis Chamberlain <mcgrof@...nel.org>, akpm@...ux-foundation.org,
 jhubbard@...dia.com, mgorman@...e.de, linux-mm@...ck.org
Cc: linux-kernel@...r.kernel.org, dave@...olabs.net, p.raghav@...sung.com,
 da.gomez@...sung.com
Subject: Re: [PATCH 3/3] mm/vmstat: simplfy extfrag_show_print with
 fragmentation_index()

On 3/14/24 01:54, Luis Chamberlain wrote:
> fragmentation_index() already uses the stack for the struct contig_page_info,
> so just use that and enhance the documentation for fragmentation_index().
> 
> Signed-off-by: Luis Chamberlain <mcgrof@...nel.org>

Reviewed-by: Vlastimil Babka <vbabka@...e.cz>

> ---
>  mm/vmstat.c | 11 +++++------
>  1 file changed, 5 insertions(+), 6 deletions(-)
> 
> diff --git a/mm/vmstat.c b/mm/vmstat.c
> index db79935e4a54..582f89b37ccf 100644
> --- a/mm/vmstat.c
> +++ b/mm/vmstat.c
> @@ -1129,7 +1129,10 @@ unsigned int extfrag_for_order(struct zone *zone, unsigned int order)
>  			info.free_pages);
>  }
>  
> -/* Same as __fragmentation index but allocs contig_page_info on stack */
> +/*
> + * Same as __fragmentation index but allocs contig_page_info on stack,
> + * useful when walking a zone as interrupts are disabled.
> + */
>  int fragmentation_index(struct zone *zone, unsigned int order)
>  {
>  	struct contig_page_info info;
> @@ -2227,15 +2230,11 @@ static void extfrag_show_print(struct seq_file *m,
>  	unsigned int order;
>  	int index;
>  
> -	/* Alloc on stack as interrupts are disabled for zone walk */
> -	struct contig_page_info info;
> -
>  	seq_printf(m, "Node %d, zone %8s ",
>  				pgdat->node_id,
>  				zone->name);
>  	for (order = 0; order < NR_PAGE_ORDERS; ++order) {
> -		fill_contig_page_info(zone, order, &info);
> -		index = __fragmentation_index(order, &info);
> +		index = fragmentation_index(zone, order);
>  		seq_printf(m, "%2d.%03d ", index / 1000, index % 1000);
>  	}
>