Re: [PATCH] mm/compaction: introduce a helper compact_zone_counters_init()

[Michal Hocko <mhocko@suse.com>]

On Tue 23-07-19 04:08:15, Yafang Shao wrote:
> This is the follow-up of the
> commit "mm/compaction.c: clear total_{migrate,free}_scanned before scanning a new zone".
> 
> These counters are used to track activities during compacting a zone,
> and they will be set to zero before compacting a new zone in all compact
> paths. Move all these common settings into compact_zone() for better
> management. A new helper compact_zone_counters_init() is introduced for
> this purpose.

The helper seems excessive a bit because we have a single call site but
other than that this is an improvement to the current fragile and
duplicated code.

I would just get rid of the helper and squash it to your previous patch
which Andrew already took to the mm tree.

> Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
> Cc: Michal Hocko <mhocko@suse.com>
> Cc: Mel Gorman <mgorman@techsingularity.net>
> Cc: Yafang Shao <shaoyafang@didiglobal.com>
> ---
>  mm/compaction.c | 28 ++++++++++++++--------------
>  1 file changed, 14 insertions(+), 14 deletions(-)
> 
> diff --git a/mm/compaction.c b/mm/compaction.c
> index a109b45..356348b 100644
> --- a/mm/compaction.c
> +++ b/mm/compaction.c
> @@ -2065,6 +2065,19 @@ bool compaction_zonelist_suitable(struct alloc_context *ac, int order,
>  	return false;
>  }
>  
> +
> +/*
> + * Bellow counters are used to track activities during compacting a zone.
> + * Before compacting a new zone, we should init these counters first.
> + */
> +static void compact_zone_counters_init(struct compact_control *cc)
> +{
> +	cc->total_migrate_scanned = 0;
> +	cc->total_free_scanned = 0;
> +	cc->nr_migratepages = 0;
> +	cc->nr_freepages = 0;
> +}
> +
>  static enum compact_result
>  compact_zone(struct compact_control *cc, struct capture_control *capc)
>  {
> @@ -2075,6 +2088,7 @@ bool compaction_zonelist_suitable(struct alloc_context *ac, int order,
>  	const bool sync = cc->mode != MIGRATE_ASYNC;
>  	bool update_cached;
>  
> +	compact_zone_counters_init(cc);
>  	cc->migratetype = gfpflags_to_migratetype(cc->gfp_mask);
>  	ret = compaction_suitable(cc->zone, cc->order, cc->alloc_flags,
>  							cc->classzone_idx);
> @@ -2278,10 +2292,6 @@ static enum compact_result compact_zone_order(struct zone *zone, int order,
>  {
>  	enum compact_result ret;
>  	struct compact_control cc = {
> -		.nr_freepages = 0,
> -		.nr_migratepages = 0,
> -		.total_migrate_scanned = 0,
> -		.total_free_scanned = 0,
>  		.order = order,
>  		.search_order = order,
>  		.gfp_mask = gfp_mask,
> @@ -2418,10 +2428,6 @@ static void compact_node(int nid)
>  		if (!populated_zone(zone))
>  			continue;
>  
> -		cc.nr_freepages = 0;
> -		cc.nr_migratepages = 0;
> -		cc.total_migrate_scanned = 0;
> -		cc.total_free_scanned = 0;
>  		cc.zone = zone;
>  		INIT_LIST_HEAD(&cc.freepages);
>  		INIT_LIST_HEAD(&cc.migratepages);
> @@ -2526,8 +2532,6 @@ static void kcompactd_do_work(pg_data_t *pgdat)
>  	struct compact_control cc = {
>  		.order = pgdat->kcompactd_max_order,
>  		.search_order = pgdat->kcompactd_max_order,
> -		.total_migrate_scanned = 0,
> -		.total_free_scanned = 0,
>  		.classzone_idx = pgdat->kcompactd_classzone_idx,
>  		.mode = MIGRATE_SYNC_LIGHT,
>  		.ignore_skip_hint = false,
> @@ -2551,10 +2555,6 @@ static void kcompactd_do_work(pg_data_t *pgdat)
>  							COMPACT_CONTINUE)
>  			continue;
>  
> -		cc.nr_freepages = 0;
> -		cc.nr_migratepages = 0;
> -		cc.total_migrate_scanned = 0;
> -		cc.total_free_scanned = 0;
>  		cc.zone = zone;
>  		INIT_LIST_HEAD(&cc.freepages);
>  		INIT_LIST_HEAD(&cc.migratepages);
> -- 
> 1.8.3.1

-- 
Michal Hocko
SUSE Labs