linux-kernel - Re: [PATCH v2 2/2] mm/mm_init.c: do not calculate zone_start_pfn/zone_end_pfn in zone_absent_pages_in

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Message-ID: <20230527080014.GD4967@kernel.org>
Date:   Sat, 27 May 2023 11:00:14 +0300
From:   Mike Rapoport <rppt@...nel.org>
To:     Haifeng Xu <haifeng.xu@...pee.com>
Cc:     akpm@...ux-foundation.org, mhocko@...e.com, david@...hat.com,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/2] mm/mm_init.c: do not calculate
 zone_start_pfn/zone_end_pfn in zone_absent_pages_in_node()

On Fri, May 26, 2023 at 08:52:51AM +0000, Haifeng Xu wrote:
> In calculate_node_totalpages(), zone_start_pfn/zone_end_pfn are already
> calculated in zone_spanned_pages_in_node(), so use them as parameters
> instead of node_start_pfn/node_end_pfn and the duplicated calculation
> process can de dropped.
> 
> Signed-off-by: Haifeng Xu <haifeng.xu@...pee.com>
> Suggested-by: Mike Rapoport <rppt@...nel.org>

Reviewed-by: Mike Rapoport (IBM) <rppt@...nel.org>

> ---
> v2:
> - remove unrelated whitespace changes
> - do not replace pgdat->node_id with a local
>   variable
> - remove redundant variable 'size'
> - add check that whether a zone is empty or not
> ---
>  mm/mm_init.c | 30 ++++++++++++------------------
>  1 file changed, 12 insertions(+), 18 deletions(-)
> 
> diff --git a/mm/mm_init.c b/mm/mm_init.c
> index f674e5798f7d..2d91bb52c619 100644
> --- a/mm/mm_init.c
> +++ b/mm/mm_init.c
> @@ -1166,20 +1166,15 @@ unsigned long __init absent_pages_in_range(unsigned long start_pfn,
>  /* Return the number of page frames in holes in a zone on a node */
>  static unsigned long __init zone_absent_pages_in_node(int nid,
>  					unsigned long zone_type,
> -					unsigned long node_start_pfn,
> -					unsigned long node_end_pfn)
> +					unsigned long zone_start_pfn,
> +					unsigned long zone_end_pfn)
>  {
> -	unsigned long zone_low = arch_zone_lowest_possible_pfn[zone_type];
> -	unsigned long zone_high = arch_zone_highest_possible_pfn[zone_type];
> -	unsigned long zone_start_pfn, zone_end_pfn;
>  	unsigned long nr_absent;
>  
> -	zone_start_pfn = clamp(node_start_pfn, zone_low, zone_high);
> -	zone_end_pfn = clamp(node_end_pfn, zone_low, zone_high);
> +	/* zone is empty, we don't have any absent pages */
> +	if (zone_start_pfn == zone_end_pfn)
> +		return 0;
>  
> -	adjust_zone_range_for_zone_movable(nid, zone_type,
> -			node_start_pfn, node_end_pfn,
> -			&zone_start_pfn, &zone_end_pfn);
>  	nr_absent = __absent_pages_in_range(nid, zone_start_pfn, zone_end_pfn);
>  
>  	/*
> @@ -1272,7 +1267,7 @@ static void __init calculate_node_totalpages(struct pglist_data *pgdat,
>  		struct zone *zone = pgdat->node_zones + i;
>  		unsigned long zone_start_pfn, zone_end_pfn;
>  		unsigned long spanned, absent;
> -		unsigned long size, real_size;
> +		unsigned long real_size;
>  
>  		spanned = zone_spanned_pages_in_node(pgdat->node_id, i,
>  						     node_start_pfn,
> @@ -1280,23 +1275,22 @@ static void __init calculate_node_totalpages(struct pglist_data *pgdat,
>  						     &zone_start_pfn,
>  						     &zone_end_pfn);
>  		absent = zone_absent_pages_in_node(pgdat->node_id, i,
> -						   node_start_pfn,
> -						   node_end_pfn);
> +						   zone_start_pfn,
> +						   zone_end_pfn);
>  
> -		size = spanned;
> -		real_size = size - absent;
> +		real_size = spanned - absent;
>  
> -		if (size)
> +		if (spanned)
>  			zone->zone_start_pfn = zone_start_pfn;
>  		else
>  			zone->zone_start_pfn = 0;
> -		zone->spanned_pages = size;
> +		zone->spanned_pages = spanned;
>  		zone->present_pages = real_size;
>  #if defined(CONFIG_MEMORY_HOTPLUG)
>  		zone->present_early_pages = real_size;
>  #endif
>  
> -		totalpages += size;
> +		totalpages += spanned;
>  		realtotalpages += real_size;
>  	}
>  
> -- 
> 2.25.1
> 

-- 
Sincerely yours,
Mike.