Re: [PATCH 2/3] mm/compaction: add and use for_each_populated_zone_pgdat() helper

[Baolin Wang <baolin.wang@linux.alibaba.com>]

On 2024/3/15 13:38, Luis Chamberlain wrote:
> On Thu, Mar 14, 2024 at 03:19:45PM +0800, Baolin Wang wrote:
>>
>>
>> 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@kernel.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.
> 
> Definitely, thanks, so we'd need something like this in addition:
> 
> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
> index 34b729fc751b..bd11d33ea14d 100644
> --- a/include/linux/mmzone.h
> +++ b/include/linux/mmzone.h
> @@ -1568,6 +1568,7 @@ static inline struct pglist_data *NODE_DATA(int nid)
>   extern struct pglist_data *first_online_pgdat(void);
>   extern struct pglist_data *next_online_pgdat(struct pglist_data *pgdat);
>   extern struct zone *next_zone(struct zone *zone);
> +extern struct zone *next_zone_pgdat(struct zone *zone, struct pglist_data *pgdat);
>   
>   /**
>    * for_each_online_pgdat - helper macro to iterate over all online nodes
> @@ -1600,7 +1601,7 @@ extern struct zone *next_zone(struct zone *zone);
>   #define for_each_populated_zone_pgdat(zone, pgdat)	\
>   	for (zone = pgdat->node_zones;			\
>   	     zone;					\
> -	     zone = next_zone(zone))			\
> +	     zone = next_zone_pgdat(zone, pgdat))	\
>   		if (!populated_zone(zone))		\
>   			; /* do nothing */		\
>   		else
> diff --git a/mm/compaction.c b/mm/compaction.c
> index 015126803017..96434f6fc1ad 100644
> --- a/mm/compaction.c
> +++ b/mm/compaction.c
> @@ -2152,7 +2152,6 @@ static unsigned int fragmentation_score_node(pg_data_t *pgdat)
>   {
>   	unsigned int score = 0;
>   	struct zone *zone;
> -	int zoneid;
>   
>   	for_each_populated_zone_pgdat(zone, pgdat)
>   		score += fragmentation_score_zone_weighted(zone);
> diff --git a/mm/mmzone.c b/mm/mmzone.c
> index c01896eca736..043a6dc16c05 100644
> --- a/mm/mmzone.c
> +++ b/mm/mmzone.c
> @@ -43,6 +43,18 @@ struct zone *next_zone(struct zone *zone)
>   	return zone;
>   }
>   
> +/*
> + * next_zone_pgdat - helper magic for for_each_zone() per node
> + */
> +struct zone *next_zone_pgdat(struct zone *zone, struct pglist_data *pgdat)
> +{
> +	if (!zone || !pgdat)
> +		return NULL;

Seems unnecessary, you already accessed them before calling 
next_zone_pgdat(). Otherwise, looks good to me.

> +	if (zone < pgdat->node_zones + MAX_NR_ZONES - 1)
> +		return ++zone;
> +	return NULL;
> +}
> +
>   static inline int zref_in_nodemask(struct zoneref *zref, nodemask_t *nodes)
>   {
>   #ifdef CONFIG_NUMA