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Message-ID: <CAHbLzkp4fa02+4p7MiRLSRJyQTrFC0x6auH9zy+ynVh1B=J87g@mail.gmail.com>
Date: Wed, 2 Dec 2020 21:01:12 -0800
From: Yang Shi <shy828301@...il.com>
To: Roman Gushchin <guro@...com>
Cc: Kirill Tkhai <ktkhai@...tuozzo.com>,
Shakeel Butt <shakeelb@...gle.com>,
Dave Chinner <david@...morbit.com>,
Johannes Weiner <hannes@...xchg.org>,
Michal Hocko <mhocko@...e.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Linux MM <linux-mm@...ck.org>,
Linux FS-devel Mailing List <linux-fsdevel@...r.kernel.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 6/9] mm: vmscan: use per memcg nr_deferred of shrinker
On Wed, Dec 2, 2020 at 7:08 PM Roman Gushchin <guro@...com> wrote:
>
> On Wed, Dec 02, 2020 at 10:27:22AM -0800, Yang Shi wrote:
> > Use per memcg's nr_deferred for memcg aware shrinkers. The shrinker's nr_deferred
> > will be used in the following cases:
> > 1. Non memcg aware shrinkers
> > 2. !CONFIG_MEMCG
> > 3. memcg is disabled by boot parameter
> >
> > Signed-off-by: Yang Shi <shy828301@...il.com>
> > ---
> > mm/vmscan.c | 88 +++++++++++++++++++++++++++++++++++++++++++++++++----
> > 1 file changed, 82 insertions(+), 6 deletions(-)
> >
> > diff --git a/mm/vmscan.c b/mm/vmscan.c
> > index cba0bc8d4661..d569fdcaba79 100644
> > --- a/mm/vmscan.c
> > +++ b/mm/vmscan.c
> > @@ -203,6 +203,12 @@ static DECLARE_RWSEM(shrinker_rwsem);
> > static DEFINE_IDR(shrinker_idr);
> > static int shrinker_nr_max;
> >
> > +static inline bool is_deferred_memcg_aware(struct shrinker *shrinker)
> > +{
> > + return (shrinker->flags & SHRINKER_MEMCG_AWARE) &&
> > + !mem_cgroup_disabled();
> > +}
> > +
> > static int prealloc_memcg_shrinker(struct shrinker *shrinker)
> > {
> > int id, ret = -ENOMEM;
> > @@ -271,7 +277,58 @@ static bool writeback_throttling_sane(struct scan_control *sc)
> > #endif
> > return false;
> > }
> > +
> > +static inline long count_nr_deferred(struct shrinker *shrinker,
> > + struct shrink_control *sc)
> > +{
> > + bool per_memcg_deferred = is_deferred_memcg_aware(shrinker) && sc->memcg;
> > + struct memcg_shrinker_deferred *deferred;
> > + struct mem_cgroup *memcg = sc->memcg;
> > + int nid = sc->nid;
> > + int id = shrinker->id;
> > + long nr;
> > +
> > + if (!(shrinker->flags & SHRINKER_NUMA_AWARE))
> > + nid = 0;
> > +
> > + if (per_memcg_deferred) {
> > + deferred = rcu_dereference_protected(memcg->nodeinfo[nid]->shrinker_deferred,
> > + true);
> > + nr = atomic_long_xchg(&deferred->nr_deferred[id], 0);
> > + } else
> > + nr = atomic_long_xchg(&shrinker->nr_deferred[nid], 0);
> > +
> > + return nr;
> > +}
> > +
> > +static inline long set_nr_deferred(long nr, struct shrinker *shrinker,
> > + struct shrink_control *sc)
> > +{
> > + bool per_memcg_deferred = is_deferred_memcg_aware(shrinker) && sc->memcg;
> > + struct memcg_shrinker_deferred *deferred;
> > + struct mem_cgroup *memcg = sc->memcg;
> > + int nid = sc->nid;
> > + int id = shrinker->id;
> > + long new_nr;
> > +
> > + if (!(shrinker->flags & SHRINKER_NUMA_AWARE))
> > + nid = 0;
> > +
> > + if (per_memcg_deferred) {
> > + deferred = rcu_dereference_protected(memcg->nodeinfo[nid]->shrinker_deferred,
> > + true);
> > + new_nr = atomic_long_add_return(nr, &deferred->nr_deferred[id]);
> > + } else
> > + new_nr = atomic_long_add_return(nr, &shrinker->nr_deferred[nid]);
> > +
> > + return new_nr;
> > +}
> > #else
> > +static inline bool is_deferred_memcg_aware(struct shrinker *shrinker)
> > +{
> > + return false;
> > +}
> > +
> > static int prealloc_memcg_shrinker(struct shrinker *shrinker)
> > {
> > return 0;
> > @@ -290,6 +347,29 @@ static bool writeback_throttling_sane(struct scan_control *sc)
> > {
> > return true;
> > }
> > +
> > +static inline long count_nr_deferred(struct shrinker *shrinker,
> > + struct shrink_control *sc)
> > +{
> > + int nid = sc->nid;
> > +
> > + if (!(shrinker->flags & SHRINKER_NUMA_AWARE))
> > + nid = 0;
> > +
> > + return atomic_long_xchg(&shrinker->nr_deferred[nid], 0);
> > +}
> > +
> > +static inline long set_nr_deferred(long nr, struct shrinker *shrinker,
> > + struct shrink_control *sc)
> > +{
> > + int nid = sc->nid;
> > +
> > + if (!(shrinker->flags & SHRINKER_NUMA_AWARE))
> > + nid = 0;
> > +
> > + return atomic_long_add_return(nr,
> > + &shrinker->nr_deferred[nid]);
> > +}
> > #endif
> >
> > /*
> > @@ -429,13 +509,10 @@ static unsigned long do_shrink_slab(struct shrink_control *shrinkctl,
> > long freeable;
> > long nr;
> > long new_nr;
> > - int nid = shrinkctl->nid;
> > long batch_size = shrinker->batch ? shrinker->batch
> > : SHRINK_BATCH;
> > long scanned = 0, next_deferred;
> >
> > - if (!(shrinker->flags & SHRINKER_NUMA_AWARE))
> > - nid = 0;
> >
> > freeable = shrinker->count_objects(shrinker, shrinkctl);
> > if (freeable == 0 || freeable == SHRINK_EMPTY)
> > @@ -446,7 +523,7 @@ static unsigned long do_shrink_slab(struct shrink_control *shrinkctl,
> > * and zero it so that other concurrent shrinker invocations
> > * don't also do this scanning work.
> > */
> > - nr = atomic_long_xchg(&shrinker->nr_deferred[nid], 0);
> > + nr = count_nr_deferred(shrinker, shrinkctl);
> >
> > total_scan = nr;
> > if (shrinker->seeks) {
> > @@ -539,8 +616,7 @@ static unsigned long do_shrink_slab(struct shrink_control *shrinkctl,
> > * move the unused scan count back into the shrinker in a
> > * manner that handles concurrent updates.
> > */
> > - new_nr = atomic_long_add_return(next_deferred,
> > - &shrinker->nr_deferred[nid]);
> > + new_nr = set_nr_deferred(next_deferred, shrinker, shrinkctl);
>
> Ok, I think patch (1) can be just merged into this and then it would make total sense.
Sure. Makes sense to me.
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