Re: [PATCH] mm/compaction: clear total_{migrate,free}_scanned before scanning a new zone

[Michal Hocko <mhocko@suse.com>]

On Mon 22-07-19 05:54:35, Yafang Shao wrote:
> total_{migrate,free}_scanned will be added to COMPACTMIGRATE_SCANNED and
> COMPACTFREE_SCANNED in compact_zone(). We should clear them before scanning
> a new zone.
> In the proc triggered compaction, we forgot clearing them.

Wouldn't it be more robust to move zeroying to compact_zone so that none
of the three current callers has to duplicate (and forget) to do that?

> Fixes: 7f354a548d1c ("mm, compaction: add vmstats for kcompactd work")
> Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
> Cc: David Rientjes <rientjes@google.com>
> Cc: Vlastimil Babka <vbabka@suse.cz>
> Cc: Yafang Shao <shaoyafang@didiglobal.com>
> ---
>  mm/compaction.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/compaction.c b/mm/compaction.c
> index 9e1b9ac..a109b45 100644
> --- a/mm/compaction.c
> +++ b/mm/compaction.c
> @@ -2405,8 +2405,6 @@ static void compact_node(int nid)
>  	struct zone *zone;
>  	struct compact_control cc = {
>  		.order = -1,
> -		.total_migrate_scanned = 0,
> -		.total_free_scanned = 0,
>  		.mode = MIGRATE_SYNC,
>  		.ignore_skip_hint = true,
>  		.whole_zone = true,
> @@ -2422,6 +2420,8 @@ static void compact_node(int nid)
>  
>  		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