linux-kernel - Re: [PATCH 2/3] mm/compaction: add and use for_each_populated_zone

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Date: Thu, 14 Mar 2024 15:19:45 +0800
From: Baolin Wang <baolin.wang@...ux.alibaba.com>
To: Luis Chamberlain <mcgrof@...nel.org>, akpm@...ux-foundation.org,
 jhubbard@...dia.com, vbabka@...e.cz, 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 2/3] mm/compaction: add and use
 for_each_populated_zone_pgdat() helper



On 2024/3/14 08:54, Luis Chamberlain wrote:
> We can just wrap most of the work done on fragmentation_score_node()
> into a pgdat helper for populated zones. Add the helper and use it.
> 
> Signed-off-by: Luis Chamberlain <mcgrof@...nel.org>
> ---
>   include/linux/mmzone.h | 8 ++++++++
>   mm/compaction.c        | 9 ++-------
>   2 files changed, 10 insertions(+), 7 deletions(-)
> 
> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
> index a497f189d988..1fd74c7100ec 100644
> --- a/include/linux/mmzone.h
> +++ b/include/linux/mmzone.h
> @@ -1597,6 +1597,14 @@ extern struct zone *next_zone(struct zone *zone);
>   			; /* do nothing */		\
>   		else
>   
> +#define for_each_populated_zone_pgdat(zone, pgdat)	\
> +	for (zone = pgdat->node_zones;			\
> +	     zone;					\
> +	     zone = next_zone(zone))			\
> +		if (!populated_zone(zone))		\
> +			; /* do nothing */		\
> +		else

I think this will break the original logics, since the next_zone() will 
iterate over all memory zones, instead of only the memory zones of the 
specified node.

>   static inline struct zone *zonelist_zone(struct zoneref *zoneref)
>   {
>   	return zoneref->zone;
> diff --git a/mm/compaction.c b/mm/compaction.c
> index b961db601df4..023a09d0786d 100644
> --- a/mm/compaction.c
> +++ b/mm/compaction.c
> @@ -2151,16 +2151,11 @@ static unsigned int fragmentation_score_zone_weighted(struct zone *zone)
>   static unsigned int fragmentation_score_node(pg_data_t *pgdat)
>   {
>   	unsigned int score = 0;
> +	struct zone *zone;
>   	int zoneid;
>   
> -	for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) {
> -		struct zone *zone;
> -
> -		zone = &pgdat->node_zones[zoneid];
> -		if (!populated_zone(zone))
> -			continue;
> +	for_each_populated_zone_pgdat(zone, pgdat)
>   		score += fragmentation_score_zone_weighted(zone);
> -	}
>   
>   	return score;
>   }