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

[Yafang Shao <laoar.shao@gmail.com>]

On Tue, Jul 23, 2019 at 4:12 PM Michal Hocko <mhocko@suse.com> wrote:
>
> 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.
>

Understood.

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

I appreciate it.

Thanks
Yafang

> > 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