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From:   Yang Shi <shy828301@gmail.com>
To:     guro@fb.com, ktkhai@virtuozzo.com, shakeelb@google.com,
        david@fromorbit.com, hannes@cmpxchg.org, mhocko@suse.com,
        akpm@linux-foundation.org
Cc:     shy828301@gmail.com, linux-mm@kvack.org,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [v4 PATCH 08/11] mm: vmscan: use per memcg nr_deferred of shrinker
Date:   Thu, 21 Jan 2021 15:06:18 -0800
Message-Id: <20210121230621.654304-9-shy828301@gmail.com>
In-Reply-To: <20210121230621.654304-1-shy828301@gmail.com>
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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@gmail.com>
---
 mm/vmscan.c | 81 +++++++++++++++++++++++++++++++++++++++++++++--------
 1 file changed, 69 insertions(+), 12 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 722aa71b13b2..d8e77ea13815 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -359,6 +359,27 @@ static void unregister_memcg_shrinker(struct shrinker *shrinker)
 	up_write(&shrinker_rwsem);
 }
 
+static long count_nr_deferred_memcg(int nid, struct shrinker *shrinker,
+				    struct mem_cgroup *memcg)
+{
+	struct shrinker_info *info;
+
+	info = rcu_dereference_protected(memcg->nodeinfo[nid]->shrinker_info,
+					 true);
+	return atomic_long_xchg(&info->nr_deferred[shrinker->id], 0);
+}
+
+static long set_nr_deferred_memcg(long nr, int nid, struct shrinker *shrinker,
+				  struct mem_cgroup *memcg)
+{
+	struct shrinker_info *info;
+
+	info = rcu_dereference_protected(memcg->nodeinfo[nid]->shrinker_info,
+					 true);
+
+	return atomic_long_add_return(nr, &info->nr_deferred[shrinker->id]);
+}
+
 static bool cgroup_reclaim(struct scan_control *sc)
 {
 	return sc->target_mem_cgroup;
@@ -397,6 +418,18 @@ static void unregister_memcg_shrinker(struct shrinker *shrinker)
 {
 }
 
+static long count_nr_deferred_memcg(int nid, struct shrinker *shrinker,
+				    struct mem_cgroup *memcg)
+{
+	return 0;
+}
+
+static long set_nr_deferred_memcg(long nr, int nid, struct shrinker *shrinker,
+				  struct mem_cgroup *memcg)
+{
+	return 0;
+}
+
 static bool cgroup_reclaim(struct scan_control *sc)
 {
 	return false;
@@ -408,6 +441,39 @@ static bool writeback_throttling_sane(struct scan_control *sc)
 }
 #endif
 
+static long count_nr_deferred(struct shrinker *shrinker,
+			      struct shrink_control *sc)
+{
+	int nid = sc->nid;
+
+	if (!(shrinker->flags & SHRINKER_NUMA_AWARE))
+		nid = 0;
+
+	if (sc->memcg &&
+	    (shrinker->flags & SHRINKER_MEMCG_AWARE))
+		return count_nr_deferred_memcg(nid, shrinker,
+					       sc->memcg);
+
+	return atomic_long_xchg(&shrinker->nr_deferred[nid], 0);
+}
+
+
+static 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;
+
+	if (sc->memcg &&
+	    (shrinker->flags & SHRINKER_MEMCG_AWARE))
+		return set_nr_deferred_memcg(nr, nid, shrinker,
+					     sc->memcg);
+
+	return atomic_long_add_return(nr, &shrinker->nr_deferred[nid]);
+}
+
 /*
  * This misses isolated pages which are not accounted for to save counters.
  * As the data only determines if reclaim or compaction continues, it is
@@ -544,14 +610,10 @@ 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)
 		return freeable;
@@ -561,7 +623,7 @@ 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) {
@@ -652,14 +714,9 @@ static unsigned long do_shrink_slab(struct shrink_control *shrinkctl,
 		next_deferred = 0;
 	/*
 	 * move the unused scan count back into the shrinker in a
-	 * manner that handles concurrent updates. If we exhausted the
-	 * scan, there is no need to do an update.
+	 * manner that handles concurrent updates.
 	 */
-	if (next_deferred > 0)
-		new_nr = atomic_long_add_return(next_deferred,
-						&shrinker->nr_deferred[nid]);
-	else
-		new_nr = atomic_long_read(&shrinker->nr_deferred[nid]);
+	new_nr = set_nr_deferred(next_deferred, shrinker, shrinkctl);
 
 	trace_mm_shrink_slab_end(shrinker, shrinkctl->nid, freed, nr, new_nr, total_scan);
 	return freed;
-- 
2.26.2