net: openvswitch: expand the meters supported number

In kernel datapath of Open vSwitch, there are only 1024
buckets of meter in one datapath. If installing more than
1024 (e.g. 8192) meters, it may lead to the performance drop.
But in some case, for example, Open vSwitch used as edge
gateway, there should be 20K at least, where meters used for
IP address bandwidth limitation.

[Open vSwitch userspace datapath has this issue too.]

For more scalable meter, this patch use meter array instead of
hash tables, and expand/shrink the array when necessary. So we
can install more meters than before in the datapath.
Introducing the struct *dp_meter_instance, it's easy to
expand meter though changing the *ti point in the struct
*dp_meter_table.

Cc: Pravin B Shelar <pshelar@ovn.org>
Cc: Andy Zhou <azhou@ovn.org>
Signed-off-by: Tonghao Zhang <xiangxia.m.yue@gmail.com>
Acked-by: Pravin B Shelar <pshelar@ovn.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/openvswitch/datapath.h

@@ -82,7 +82,7 @@ struct datapath {
 	u32 max_headroom;
 
 	/* Switch meters. */
-	struct hlist_head *meters;
+	struct dp_meter_table meter_tbl;
 };
 
 /**

net/openvswitch/meter.c

@@ -19,8 +19,6 @@
 #include "datapath.h"
 #include "meter.h"
 
-#define METER_HASH_BUCKETS 1024
-
 static const struct nla_policy meter_policy[OVS_METER_ATTR_MAX + 1] = {
 	[OVS_METER_ATTR_ID] = { .type = NLA_U32, },
 	[OVS_METER_ATTR_KBPS] = { .type = NLA_FLAG },
@@ -39,6 +37,11 @@ static const struct nla_policy band_policy[OVS_BAND_ATTR_MAX + 1] = {
 	[OVS_BAND_ATTR_STATS] = { .len = sizeof(struct ovs_flow_stats) },
 };
 
+static u32 meter_hash(struct dp_meter_instance *ti, u32 id)
+{
+	return id % ti->n_meters;
+}
+
 static void ovs_meter_free(struct dp_meter *meter)
 {
 	if (!meter)
@@ -47,40 +50,153 @@ static void ovs_meter_free(struct dp_meter *meter)
 	kfree_rcu(meter, rcu);
 }
 
-static struct hlist_head *meter_hash_bucket(const struct datapath *dp,
-					    u32 meter_id)
-{
-	return &dp->meters[meter_id & (METER_HASH_BUCKETS - 1)];
-}
-
 /* Call with ovs_mutex or RCU read lock. */
-static struct dp_meter *lookup_meter(const struct datapath *dp,
+static struct dp_meter *lookup_meter(const struct dp_meter_table *tbl,
 				     u32 meter_id)
 {
+	struct dp_meter_instance *ti = rcu_dereference_ovsl(tbl->ti);
+	u32 hash = meter_hash(ti, meter_id);
 	struct dp_meter *meter;
-	struct hlist_head *head;
 
-	head = meter_hash_bucket(dp, meter_id);
-	hlist_for_each_entry_rcu(meter, head, dp_hash_node,
-				lockdep_ovsl_is_held()) {
-		if (meter->id == meter_id)
+	meter = rcu_dereference_ovsl(ti->dp_meters[hash]);
+	if (meter && likely(meter->id == meter_id))
 		return meter;
-	}
+
 	return NULL;
 }
 
-static void attach_meter(struct datapath *dp, struct dp_meter *meter)
+static struct dp_meter_instance *dp_meter_instance_alloc(const u32 size)
+{
+	struct dp_meter_instance *ti;
+
+	ti = kvzalloc(sizeof(*ti) +
+		      sizeof(struct dp_meter *) * size,
+		      GFP_KERNEL);
+	if (!ti)
+		return NULL;
+
+	ti->n_meters = size;
+
+	return ti;
+}
+
+static void dp_meter_instance_free(struct dp_meter_instance *ti)
+{
+	kvfree(ti);
+}
+
+static void dp_meter_instance_free_rcu(struct rcu_head *rcu)
+{
+	struct dp_meter_instance *ti;
+
+	ti = container_of(rcu, struct dp_meter_instance, rcu);
+	kvfree(ti);
+}
+
+static int
+dp_meter_instance_realloc(struct dp_meter_table *tbl, u32 size)
+{
+	struct dp_meter_instance *ti = rcu_dereference_ovsl(tbl->ti);
+	int n_meters = min(size, ti->n_meters);
+	struct dp_meter_instance *new_ti;
+	int i;
+
+	new_ti = dp_meter_instance_alloc(size);
+	if (!new_ti)
+		return -ENOMEM;
+
+	for (i = 0; i < n_meters; i++)
+		new_ti->dp_meters[i] =
+			rcu_dereference_ovsl(ti->dp_meters[i]);
+
+	rcu_assign_pointer(tbl->ti, new_ti);
+	call_rcu(&ti->rcu, dp_meter_instance_free_rcu);
+
+	return 0;
+}
+
+static void dp_meter_instance_insert(struct dp_meter_instance *ti,
+				     struct dp_meter *meter)
 {
-	struct hlist_head *head = meter_hash_bucket(dp, meter->id);
+	u32 hash;
 
-	hlist_add_head_rcu(&meter->dp_hash_node, head);
+	hash = meter_hash(ti, meter->id);
+	rcu_assign_pointer(ti->dp_meters[hash], meter);
 }
 
-static void detach_meter(struct dp_meter *meter)
+static void dp_meter_instance_remove(struct dp_meter_instance *ti,
+				     struct dp_meter *meter)
 {
+	u32 hash;
+
+	hash = meter_hash(ti, meter->id);
+	RCU_INIT_POINTER(ti->dp_meters[hash], NULL);
+}
+
+static int attach_meter(struct dp_meter_table *tbl, struct dp_meter *meter)
+{
+	struct dp_meter_instance *ti = rcu_dereference_ovsl(tbl->ti);
+	u32 hash = meter_hash(ti, meter->id);
+
+	/* In generally, slots selected should be empty, because
+	 * OvS uses id-pool to fetch a available id.
+	 */
+	if (unlikely(rcu_dereference_ovsl(ti->dp_meters[hash])))
+		return -EBUSY;
+
+	dp_meter_instance_insert(ti, meter);
+
+	/* That function is thread-safe. */
+	if (++tbl->count >= ti->n_meters)
+		if (dp_meter_instance_realloc(tbl, ti->n_meters * 2))
+			goto expand_err;
+
+	return 0;
+
+expand_err:
+	dp_meter_instance_remove(ti, meter);
+	tbl->count--;
+	return -ENOMEM;
+}
+
+static int detach_meter(struct dp_meter_table *tbl, struct dp_meter *meter)
+{
+	struct dp_meter_instance *ti;
+
 	ASSERT_OVSL();
-	if (meter)
-		hlist_del_rcu(&meter->dp_hash_node);
+	if (!meter)
+		return 0;
+
+	ti = rcu_dereference_ovsl(tbl->ti);
+	dp_meter_instance_remove(ti, meter);
+
+	tbl->count--;
+
+	/* Shrink the meter array if necessary. */
+	if (ti->n_meters > DP_METER_ARRAY_SIZE_MIN &&
+	    tbl->count <= (ti->n_meters / 4)) {
+		int half_size = ti->n_meters / 2;
+		int i;
+
+		/* Avoid hash collision, don't move slots to other place.
+		 * Make sure there are no references of meters in array
+		 * which will be released.
+		 */
+		for (i = half_size; i < ti->n_meters; i++)
+			if (rcu_dereference_ovsl(ti->dp_meters[i]))
+				goto out;
+
+		if (dp_meter_instance_realloc(tbl, half_size))
+			goto shrink_err;
+	}
+
+out:
+	return 0;
+
+shrink_err:
+	dp_meter_instance_insert(ti, meter);
+	tbl->count++;
+	return -ENOMEM;
 }
 
 static struct sk_buff *
@@ -273,6 +389,7 @@ static int ovs_meter_cmd_set(struct sk_buff *skb, struct genl_info *info)
 	struct sk_buff *reply;
 	struct ovs_header *ovs_reply_header;
 	struct ovs_header *ovs_header = info->userhdr;
+	struct dp_meter_table *meter_tbl;
 	struct datapath *dp;
 	int err;
 	u32 meter_id;
@@ -300,12 +417,18 @@ static int ovs_meter_cmd_set(struct sk_buff *skb, struct genl_info *info)
 		goto exit_unlock;
 	}
 
+	meter_tbl = &dp->meter_tbl;
 	meter_id = nla_get_u32(a[OVS_METER_ATTR_ID]);
 
-	/* Cannot fail after this. */
-	old_meter = lookup_meter(dp, meter_id);
-	detach_meter(old_meter);
-	attach_meter(dp, meter);
+	old_meter = lookup_meter(meter_tbl, meter_id);
+	err = detach_meter(meter_tbl, old_meter);
+	if (err)
+		goto exit_unlock;
+
+	err = attach_meter(meter_tbl, meter);
+	if (err)
+		goto exit_unlock;
+
 	ovs_unlock();
 
 	/* Build response with the meter_id and stats from
@@ -337,14 +460,14 @@ static int ovs_meter_cmd_set(struct sk_buff *skb, struct genl_info *info)
 
 static int ovs_meter_cmd_get(struct sk_buff *skb, struct genl_info *info)
 {
-	struct nlattr **a = info->attrs;
-	u32 meter_id;
 	struct ovs_header *ovs_header = info->userhdr;
 	struct ovs_header *ovs_reply_header;
+	struct nlattr **a = info->attrs;
+	struct dp_meter *meter;
+	struct sk_buff *reply;
 	struct datapath *dp;
+	u32 meter_id;
 	int err;
-	struct sk_buff *reply;
-	struct dp_meter *meter;
 
 	if (!a[OVS_METER_ATTR_ID])
 		return -EINVAL;
@@ -365,7 +488,7 @@ static int ovs_meter_cmd_get(struct sk_buff *skb, struct genl_info *info)
 	}
 
 	/* Locate meter, copy stats. */
-	meter = lookup_meter(dp, meter_id);
+	meter = lookup_meter(&dp->meter_tbl, meter_id);
 	if (!meter) {
 		err = -ENOENT;
 		goto exit_unlock;
@@ -390,18 +513,17 @@ static int ovs_meter_cmd_get(struct sk_buff *skb, struct genl_info *info)
 
 static int ovs_meter_cmd_del(struct sk_buff *skb, struct genl_info *info)
 {
-	struct nlattr **a = info->attrs;
-	u32 meter_id;
 	struct ovs_header *ovs_header = info->userhdr;
 	struct ovs_header *ovs_reply_header;
+	struct nlattr **a = info->attrs;
+	struct dp_meter *old_meter;
+	struct sk_buff *reply;
 	struct datapath *dp;
+	u32 meter_id;
 	int err;
-	struct sk_buff *reply;
-	struct dp_meter *old_meter;
 
 	if (!a[OVS_METER_ATTR_ID])
 		return -EINVAL;
-	meter_id = nla_get_u32(a[OVS_METER_ATTR_ID]);
 
 	reply = ovs_meter_cmd_reply_start(info, OVS_METER_CMD_DEL,
 					  &ovs_reply_header);
@@ -416,14 +538,19 @@ static int ovs_meter_cmd_del(struct sk_buff *skb, struct genl_info *info)
 		goto exit_unlock;
 	}
 
-	old_meter = lookup_meter(dp, meter_id);
+	meter_id = nla_get_u32(a[OVS_METER_ATTR_ID]);
+	old_meter = lookup_meter(&dp->meter_tbl, meter_id);
 	if (old_meter) {
 		spin_lock_bh(&old_meter->lock);
 		err = ovs_meter_cmd_reply_stats(reply, meter_id, old_meter);
 		WARN_ON(err);
 		spin_unlock_bh(&old_meter->lock);
-		detach_meter(old_meter);
+
+		err = detach_meter(&dp->meter_tbl, old_meter);
+		if (err)
+			goto exit_unlock;
 	}
+
 	ovs_unlock();
 	ovs_meter_free(old_meter);
 	genlmsg_end(reply, ovs_reply_header);
@@ -443,16 +570,16 @@ static int ovs_meter_cmd_del(struct sk_buff *skb, struct genl_info *info)
 bool ovs_meter_execute(struct datapath *dp, struct sk_buff *skb,
 		       struct sw_flow_key *key, u32 meter_id)
 {
-	struct dp_meter *meter;
-	struct dp_meter_band *band;
 	long long int now_ms = div_u64(ktime_get_ns(), 1000 * 1000);
 	long long int long_delta_ms;
-	u32 delta_ms;
-	u32 cost;
+	struct dp_meter_band *band;
+	struct dp_meter *meter;
 	int i, band_exceeded_max = -1;
 	u32 band_exceeded_rate = 0;
+	u32 delta_ms;
+	u32 cost;
 
-	meter = lookup_meter(dp, meter_id);
+	meter = lookup_meter(&dp->meter_tbl, meter_id);
 	/* Do not drop the packet when there is no meter. */
 	if (!meter)
 		return false;
@@ -570,32 +697,27 @@ struct genl_family dp_meter_genl_family __ro_after_init = {
 
 int ovs_meters_init(struct datapath *dp)
 {
-	int i;
-
-	dp->meters = kmalloc_array(METER_HASH_BUCKETS,
-				   sizeof(struct hlist_head), GFP_KERNEL);
+	struct dp_meter_table *tbl = &dp->meter_tbl;
+	struct dp_meter_instance *ti;
 
-	if (!dp->meters)
+	ti = dp_meter_instance_alloc(DP_METER_ARRAY_SIZE_MIN);
+	if (!ti)
 		return -ENOMEM;
 
-	for (i = 0; i < METER_HASH_BUCKETS; i++)
-		INIT_HLIST_HEAD(&dp->meters[i]);
+	rcu_assign_pointer(tbl->ti, ti);
+	tbl->count = 0;
 
 	return 0;
 }
 
 void ovs_meters_exit(struct datapath *dp)
 {
+	struct dp_meter_table *tbl = &dp->meter_tbl;
+	struct dp_meter_instance *ti = rcu_dereference_raw(tbl->ti);
 	int i;
 
-	for (i = 0; i < METER_HASH_BUCKETS; i++) {
-		struct hlist_head *head = &dp->meters[i];
-		struct dp_meter *meter;
-		struct hlist_node *n;
-
-		hlist_for_each_entry_safe(meter, n, head, dp_hash_node)
-			kfree(meter);
-	}
+	for (i = 0; i < ti->n_meters; i++)
+		ovs_meter_free(ti->dp_meters[i]);
 
-	kfree(dp->meters);
+	dp_meter_instance_free(ti);
 }

net/openvswitch/meter.h

@@ -13,11 +13,13 @@
 #include <linux/openvswitch.h>
 #include <linux/genetlink.h>
 #include <linux/skbuff.h>
+#include <linux/bits.h>
 
 #include "flow.h"
 struct datapath;
 
 #define DP_MAX_BANDS		1
+#define DP_METER_ARRAY_SIZE_MIN	BIT_ULL(10)
 
 struct dp_meter_band {
 	u32 type;
@@ -30,9 +32,6 @@ struct dp_meter_band {
 struct dp_meter {
 	spinlock_t lock;    /* Per meter lock */
 	struct rcu_head rcu;
-	struct hlist_node dp_hash_node; /*Element in datapath->meters
-					 * hash table.
-					 */
 	u32 id;
 	u16 kbps:1, keep_stats:1;
 	u16 n_bands;
@@ -42,6 +41,17 @@ struct dp_meter {
 	struct dp_meter_band bands[];
 };
 
+struct dp_meter_instance {
+	struct rcu_head rcu;
+	u32 n_meters;
+	struct dp_meter __rcu *dp_meters[];
+};
+
+struct dp_meter_table {
+	struct dp_meter_instance __rcu *ti;
+	u32 count;
+};
+
 extern struct genl_family dp_meter_genl_family;
 int ovs_meters_init(struct datapath *dp);
 void ovs_meters_exit(struct datapath *dp);