net/mlx5: Change flow counters addlist type to single linked list

In order to prevent flow counters stats work function from traversing whole
flow counters tree while searching for deleted flow counters, new list to
store deleted flow counters will be added to struct mlx5_fc_stats. However,
the flow counter structure itself has no space left to store any more data
in first cache line. To free space that is needed to store additional list
node, convert current addlist double linked list (two pointers per node) to
atomic single linked list (one pointer per node).

Lockless NULL-terminated single linked list data type doesn't require any
additional external synchronization for operations used by flow counters
module (add single new element, remove all elements from list and traverse
them). Remove addlist_lock that is no longer needed.

Signed-off-by: Vlad Buslov <vladbu@mellanox.com>
Acked-by: Amir Vadai <amir@vadai.me>
Reviewed-by: Paul Blakey <paulb@mellanox.com>
Reviewed-by: Roi Dayan <roid@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/fs_core.h b/drivers/net/ethernet/mellanox/mlx5/core/fs_core.h
index 32070e5d993d856d0c560e9adde78b3e86d928bf..f68590291e0cd48ed160c02195f0589bd1cb9e74 100644 (file)
--- a/drivers/net/ethernet/mellanox/mlx5/core/fs_core.h
+++ b/drivers/net/ethernet/mellanox/mlx5/core/fs_core.h
@@ -36,6 +36,7 @@
 #include <linux/refcount.h>
 #include <linux/mlx5/fs.h>
 #include <linux/rhashtable.h>
+#include <linux/llist.h>
 
 enum fs_node_type {
        FS_TYPE_NAMESPACE,
@@ -139,7 +140,7 @@ struct mlx5_fc_cache {
 
 struct mlx5_fc {
        struct rb_node node;
-       struct list_head list;
+       struct llist_node addlist;
 
        /* last{packets,bytes} members are used when calculating the delta since
         * last reading

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/fs_counters.c b/drivers/net/ethernet/mellanox/mlx5/core/fs_counters.c
index 58af6be13dfa88a2e08d5d85dd54b3fdaeb4e4f6..d996d6cf9e198a59e49c4e2f7b40f118a51af8ac 100644 (file)
--- a/drivers/net/ethernet/mellanox/mlx5/core/fs_counters.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/fs_counters.c
@@ -52,7 +52,9 @@
  * access to counter list:
  * - create (user context)
  *   - mlx5_fc_create() only adds to an addlist to be used by
- *     mlx5_fc_stats_query_work(). addlist is protected by a spinlock.
+ *     mlx5_fc_stats_query_work(). addlist is a lockless single linked list
+ *     that doesn't require any additional synchronization when adding single
+ *     node.
  *   - spawn thread to do the actual destroy
  *
  * - destroy (user context)
@@ -156,28 +158,29 @@ out:
        return node;
 }
 
+static void mlx5_free_fc(struct mlx5_core_dev *dev,
+                        struct mlx5_fc *counter)
+{
+       mlx5_cmd_fc_free(dev, counter->id);
+       kfree(counter);
+}
+
 static void mlx5_fc_stats_work(struct work_struct *work)
 {
        struct mlx5_core_dev *dev = container_of(work, struct mlx5_core_dev,
                                                 priv.fc_stats.work.work);
        struct mlx5_fc_stats *fc_stats = &dev->priv.fc_stats;
+       struct llist_node *tmplist = llist_del_all(&fc_stats->addlist);
        unsigned long now = jiffies;
        struct mlx5_fc *counter = NULL;
        struct mlx5_fc *last = NULL;
        struct rb_node *node;
-       LIST_HEAD(tmplist);
-
-       spin_lock(&fc_stats->addlist_lock);
 
-       list_splice_tail_init(&fc_stats->addlist, &tmplist);
-
-       if (!list_empty(&tmplist) || !RB_EMPTY_ROOT(&fc_stats->counters))
+       if (tmplist || !RB_EMPTY_ROOT(&fc_stats->counters))
                queue_delayed_work(fc_stats->wq, &fc_stats->work,
                                   fc_stats->sampling_interval);
 
-       spin_unlock(&fc_stats->addlist_lock);
-
-       list_for_each_entry(counter, &tmplist, list)
+       llist_for_each_entry(counter, tmplist, addlist)
                mlx5_fc_stats_insert(&fc_stats->counters, counter);
 
        node = rb_first(&fc_stats->counters);
@@ -229,9 +232,7 @@ struct mlx5_fc *mlx5_fc_create(struct mlx5_core_dev *dev, bool aging)
                counter->cache.lastuse = jiffies;
                counter->aging = true;
 
-               spin_lock(&fc_stats->addlist_lock);
-               list_add(&counter->list, &fc_stats->addlist);
-               spin_unlock(&fc_stats->addlist_lock);
+               llist_add(&counter->addlist, &fc_stats->addlist);
 
                mod_delayed_work(fc_stats->wq, &fc_stats->work, 0);
        }
@@ -268,8 +269,7 @@ int mlx5_init_fc_stats(struct mlx5_core_dev *dev)
        struct mlx5_fc_stats *fc_stats = &dev->priv.fc_stats;
 
        fc_stats->counters = RB_ROOT;
-       INIT_LIST_HEAD(&fc_stats->addlist);
-       spin_lock_init(&fc_stats->addlist_lock);
+       init_llist_head(&fc_stats->addlist);
 
        fc_stats->wq = create_singlethread_workqueue("mlx5_fc");
        if (!fc_stats->wq)
@@ -284,6 +284,7 @@ int mlx5_init_fc_stats(struct mlx5_core_dev *dev)
 void mlx5_cleanup_fc_stats(struct mlx5_core_dev *dev)
 {
        struct mlx5_fc_stats *fc_stats = &dev->priv.fc_stats;
+       struct llist_node *tmplist;
        struct mlx5_fc *counter;
        struct mlx5_fc *tmp;
        struct rb_node *node;
@@ -292,13 +293,9 @@ void mlx5_cleanup_fc_stats(struct mlx5_core_dev *dev)
        destroy_workqueue(dev->priv.fc_stats.wq);
        dev->priv.fc_stats.wq = NULL;
 
-       list_for_each_entry_safe(counter, tmp, &fc_stats->addlist, list) {
-               list_del(&counter->list);
-
-               mlx5_cmd_fc_free(dev, counter->id);
-
-               kfree(counter);
-       }
+       tmplist = llist_del_all(&fc_stats->addlist);
+       llist_for_each_entry_safe(counter, tmp, tmplist, addlist)
+               mlx5_free_fc(dev, counter);
 
        node = rb_first(&fc_stats->counters);
        while (node) {
@@ -308,9 +305,7 @@ void mlx5_cleanup_fc_stats(struct mlx5_core_dev *dev)
 
                rb_erase(&counter->node, &fc_stats->counters);
 
-               mlx5_cmd_fc_free(dev, counter->id);
-
-               kfree(counter);
+               mlx5_free_fc(dev, counter);
        }
 }
 

diff --git a/include/linux/mlx5/driver.h b/include/linux/mlx5/driver.h
index 7a452716de4be0a7902f26ccc97ce124c6b168ff..c00549293982ebf305d8e4ac05829d05f6b6c0b2 100644 (file)
--- a/include/linux/mlx5/driver.h
+++ b/include/linux/mlx5/driver.h
@@ -584,9 +584,7 @@ struct mlx5_irq_info {
 
 struct mlx5_fc_stats {
        struct rb_root counters;
-       struct list_head addlist;
-       /* protect addlist add/splice operations */
-       spinlock_t addlist_lock;
+       struct llist_head addlist;
 
        struct workqueue_struct *wq;
        struct delayed_work work;