Re: [PATCH v2 1/7] mm: vmscan: add a map_nr_max field to shrinker_info

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On 2023/2/23 21:27, Qi Zheng wrote:
To prepare for the subsequent lockless memcg slab shrink,
add a map_nr_max field to struct shrinker_info to records
its own real shrinker_nr_max.

No functional changes.

Signed-off-by: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>

I missed Suggested-by here, hi Kirill, can I add it?

Suggested-by: Kirill Tkhai <tkhai@xxxxx>

---
  include/linux/memcontrol.h |  1 +
  mm/vmscan.c                | 29 ++++++++++++++++++-----------
  2 files changed, 19 insertions(+), 11 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index b6eda2ab205d..aa69ea98e2d8 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -97,6 +97,7 @@ struct shrinker_info {
  	struct rcu_head rcu;
  	atomic_long_t *nr_deferred;
  	unsigned long *map;
+	int map_nr_max;
  };
struct lruvec_stats_percpu {
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 9c1c5e8b24b8..9f895ca6216c 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -224,9 +224,16 @@ static struct shrinker_info *shrinker_info_protected(struct mem_cgroup *memcg,
  					 lockdep_is_held(&shrinker_rwsem));
  }
+static inline bool need_expand(int new_nr_max, int old_nr_max)
+{
+	return round_up(new_nr_max, BITS_PER_LONG) >
+	       round_up(old_nr_max, BITS_PER_LONG);
+}
+
  static int expand_one_shrinker_info(struct mem_cgroup *memcg,
  				    int map_size, int defer_size,
-				    int old_map_size, int old_defer_size)
+				    int old_map_size, int old_defer_size,
+				    int new_nr_max)
  {
  	struct shrinker_info *new, *old;
  	struct mem_cgroup_per_node *pn;
@@ -240,12 +247,16 @@ static int expand_one_shrinker_info(struct mem_cgroup *memcg,
  		if (!old)
  			return 0;
+ if (!need_expand(new_nr_max, old->map_nr_max))
+			return 0;
+
  		new = kvmalloc_node(sizeof(*new) + size, GFP_KERNEL, nid);
  		if (!new)
  			return -ENOMEM;
new->nr_deferred = (atomic_long_t *)(new + 1);
  		new->map = (void *)new->nr_deferred + defer_size;
+		new->map_nr_max = new_nr_max;
/* map: set all old bits, clear all new bits */
  		memset(new->map, (int)0xff, old_map_size);
@@ -295,6 +306,7 @@ int alloc_shrinker_info(struct mem_cgroup *memcg)
  		}
  		info->nr_deferred = (atomic_long_t *)(info + 1);
  		info->map = (void *)info->nr_deferred + defer_size;
+		info->map_nr_max = shrinker_nr_max;
  		rcu_assign_pointer(memcg->nodeinfo[nid]->shrinker_info, info);
  	}
  	up_write(&shrinker_rwsem);
@@ -302,12 +314,6 @@ int alloc_shrinker_info(struct mem_cgroup *memcg)
  	return ret;
  }
-static inline bool need_expand(int nr_max)
-{
-	return round_up(nr_max, BITS_PER_LONG) >
-	       round_up(shrinker_nr_max, BITS_PER_LONG);
-}
-
  static int expand_shrinker_info(int new_id)
  {
  	int ret = 0;
@@ -316,7 +322,7 @@ static int expand_shrinker_info(int new_id)
  	int old_map_size, old_defer_size = 0;
  	struct mem_cgroup *memcg;
- if (!need_expand(new_nr_max))
+	if (!need_expand(new_nr_max, shrinker_nr_max))
  		goto out;
if (!root_mem_cgroup)
@@ -332,7 +338,8 @@ static int expand_shrinker_info(int new_id)
  	memcg = mem_cgroup_iter(NULL, NULL, NULL);
  	do {
  		ret = expand_one_shrinker_info(memcg, map_size, defer_size,
-					       old_map_size, old_defer_size);
+					       old_map_size, old_defer_size,
+					       new_nr_max);
  		if (ret) {
  			mem_cgroup_iter_break(NULL, memcg);
  			goto out;
@@ -432,7 +439,7 @@ void reparent_shrinker_deferred(struct mem_cgroup *memcg)
  	for_each_node(nid) {
  		child_info = shrinker_info_protected(memcg, nid);
  		parent_info = shrinker_info_protected(parent, nid);
-		for (i = 0; i < shrinker_nr_max; i++) {
+		for (i = 0; i < child_info->map_nr_max; i++) {
  			nr = atomic_long_read(&child_info->nr_deferred[i]);
  			atomic_long_add(nr, &parent_info->nr_deferred[i]);
  		}
@@ -899,7 +906,7 @@ static unsigned long shrink_slab_memcg(gfp_t gfp_mask, int nid,
  	if (unlikely(!info))
  		goto unlock;
- for_each_set_bit(i, info->map, shrinker_nr_max) {
+	for_each_set_bit(i, info->map, info->map_nr_max) {
  		struct shrink_control sc = {
  			.gfp_mask = gfp_mask,
  			.nid = nid,

--
Thanks,
Qi




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