[PATCH net-next 2/2] net: openvswitch: make masks cache size configurable

[Eelco Chaudron <echaudro@redhat.com>]

This patch makes the masks cache size configurable, or with
a size of 0, disable it.

Reviewed-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Eelco Chaudron <echaudro@redhat.com>
---
 include/uapi/linux/openvswitch.h |    1 
 net/openvswitch/datapath.c       |   11 +++++
 net/openvswitch/flow_table.c     |   86 ++++++++++++++++++++++++++++++++++----
 net/openvswitch/flow_table.h     |   10 ++++
 4 files changed, 98 insertions(+), 10 deletions(-)

diff --git a/include/uapi/linux/openvswitch.h b/include/uapi/linux/openvswitch.h
index 7cb76e5ca7cf..8300cc29dec8 100644
--- a/include/uapi/linux/openvswitch.h
+++ b/include/uapi/linux/openvswitch.h
@@ -86,6 +86,7 @@ enum ovs_datapath_attr {
 	OVS_DP_ATTR_MEGAFLOW_STATS,	/* struct ovs_dp_megaflow_stats */
 	OVS_DP_ATTR_USER_FEATURES,	/* OVS_DP_F_*  */
 	OVS_DP_ATTR_PAD,
+	OVS_DP_ATTR_MASKS_CACHE_SIZE,
 	__OVS_DP_ATTR_MAX
 };
 
diff --git a/net/openvswitch/datapath.c b/net/openvswitch/datapath.c
index a54df1fe3ec4..f08aa1fb9f4b 100644
--- a/net/openvswitch/datapath.c
+++ b/net/openvswitch/datapath.c
@@ -1535,6 +1535,10 @@ static int ovs_dp_cmd_fill_info(struct datapath *dp, struct sk_buff *skb,
 	if (nla_put_u32(skb, OVS_DP_ATTR_USER_FEATURES, dp->user_features))
 		goto nla_put_failure;
 
+	if (nla_put_u32(skb, OVS_DP_ATTR_MASKS_CACHE_SIZE,
+			ovs_flow_tbl_masks_cache_size(&dp->table)))
+		goto nla_put_failure;
+
 	genlmsg_end(skb, ovs_header);
 	return 0;
 
@@ -1599,6 +1603,13 @@ static int ovs_dp_change(struct datapath *dp, struct nlattr *a[])
 #endif
 	}
 
+	if (a[OVS_DP_ATTR_MASKS_CACHE_SIZE]) {
+		u32 cache_size;
+
+		cache_size = nla_get_u32(a[OVS_DP_ATTR_MASKS_CACHE_SIZE]);
+		ovs_flow_tbl_masks_cache_resize(&dp->table, cache_size);
+	}
+
 	dp->user_features = user_features;
 
 	if (dp->user_features & OVS_DP_F_TC_RECIRC_SHARING)
diff --git a/net/openvswitch/flow_table.c b/net/openvswitch/flow_table.c
index a5912ea05352..1c3590bcf28b 100644
--- a/net/openvswitch/flow_table.c
+++ b/net/openvswitch/flow_table.c
@@ -38,8 +38,8 @@
 #define MASK_ARRAY_SIZE_MIN	16
 #define REHASH_INTERVAL		(10 * 60 * HZ)
 
+#define MC_DEFAULT_HASH_ENTRIES	256
 #define MC_HASH_SHIFT		8
-#define MC_HASH_ENTRIES		(1u << MC_HASH_SHIFT)
 #define MC_HASH_SEGS		((sizeof(uint32_t) * 8) / MC_HASH_SHIFT)
 
 static struct kmem_cache *flow_cache;
@@ -341,14 +341,74 @@ static void flow_mask_remove(struct flow_table *tbl, struct sw_flow_mask *mask)
 	}
 }
 
+static void __mask_cache_destroy(struct mask_cache *mc)
+{
+	if (mc->mask_cache)
+		free_percpu(mc->mask_cache);
+	kfree(mc);
+}
+
+static void mask_cache_rcu_cb(struct rcu_head *rcu)
+{
+	struct mask_cache *mc = container_of(rcu, struct mask_cache, rcu);
+
+	__mask_cache_destroy(mc);
+}
+
+static struct mask_cache *tbl_mask_cache_alloc(u32 size)
+{
+	struct mask_cache_entry *cache = NULL;
+	struct mask_cache *new;
+
+	/* Only allow size to be 0, or a power of 2, and does not exceed
+	 * percpu allocation size.
+	 */
+	if ((size & (size - 1)) != 0 ||
+	    (size * sizeof(struct mask_cache_entry)) > PCPU_MIN_UNIT_SIZE)
+		return NULL;
+
+	new = kzalloc(sizeof(*new), GFP_KERNEL);
+	if (!new)
+		return NULL;
+
+	new->cache_size = size;
+	if (new->cache_size > 0) {
+		cache = __alloc_percpu(sizeof(struct mask_cache_entry) *
+				       new->cache_size,
+				       __alignof__(struct mask_cache_entry));
+
+		if (!cache) {
+			kfree(new);
+			return NULL;
+		}
+	}
+
+	new->mask_cache = cache;
+	return new;
+}
+
+void ovs_flow_tbl_masks_cache_resize(struct flow_table *table, u32 size)
+{
+	struct mask_cache *mc = rcu_dereference(table->mask_cache);
+	struct mask_cache *new;
+
+	if (size == mc->cache_size || (size & (size - 1)) != 0)
+		return;
+
+	new = tbl_mask_cache_alloc(size);
+	if (!new)
+		return;
+
+	rcu_assign_pointer(table->mask_cache, new);
+	call_rcu(&mc->rcu, mask_cache_rcu_cb);
+}
+
 int ovs_flow_tbl_init(struct flow_table *table)
 {
 	struct table_instance *ti, *ufid_ti;
 	struct mask_array *ma;
 
-	table->mask_cache = __alloc_percpu(sizeof(struct mask_cache_entry) *
-					   MC_HASH_ENTRIES,
-					   __alignof__(struct mask_cache_entry));
+	table->mask_cache = tbl_mask_cache_alloc(MC_DEFAULT_HASH_ENTRIES);
 	if (!table->mask_cache)
 		return -ENOMEM;
 
@@ -377,7 +437,7 @@ int ovs_flow_tbl_init(struct flow_table *table)
 free_mask_array:
 	__mask_array_destroy(ma);
 free_mask_cache:
-	free_percpu(table->mask_cache);
+	__mask_cache_destroy(table->mask_cache);
 	return -ENOMEM;
 }
 
@@ -454,7 +514,7 @@ void ovs_flow_tbl_destroy(struct flow_table *table)
 	struct table_instance *ti = rcu_dereference_raw(table->ti);
 	struct table_instance *ufid_ti = rcu_dereference_raw(table->ufid_ti);
 
-	free_percpu(table->mask_cache);
+	call_rcu(&table->mask_cache->rcu, mask_cache_rcu_cb);
 	call_rcu(&table->mask_array->rcu, mask_array_rcu_cb);
 	table_instance_destroy(table, ti, ufid_ti, false);
 }
@@ -724,6 +784,7 @@ struct sw_flow *ovs_flow_tbl_lookup_stats(struct flow_table *tbl,
 					  u32 *n_mask_hit,
 					  u32 *n_cache_hit)
 {
+	struct mask_cache *mc = rcu_dereference(tbl->mask_cache);
 	struct mask_array *ma = rcu_dereference(tbl->mask_array);
 	struct table_instance *ti = rcu_dereference(tbl->ti);
 	struct mask_cache_entry *entries, *ce;
@@ -733,7 +794,7 @@ struct sw_flow *ovs_flow_tbl_lookup_stats(struct flow_table *tbl,
 
 	*n_mask_hit = 0;
 	*n_cache_hit = 0;
-	if (unlikely(!skb_hash)) {
+	if (unlikely(!skb_hash || mc->cache_size == 0)) {
 		u32 mask_index = 0;
 		u32 cache = 0;
 
@@ -749,11 +810,11 @@ struct sw_flow *ovs_flow_tbl_lookup_stats(struct flow_table *tbl,
 
 	ce = NULL;
 	hash = skb_hash;
-	entries = this_cpu_ptr(tbl->mask_cache);
+	entries = this_cpu_ptr(mc->mask_cache);
 
 	/* Find the cache entry 'ce' to operate on. */
 	for (seg = 0; seg < MC_HASH_SEGS; seg++) {
-		int index = hash & (MC_HASH_ENTRIES - 1);
+		int index = hash & (mc->cache_size - 1);
 		struct mask_cache_entry *e;
 
 		e = &entries[index];
@@ -867,6 +928,13 @@ int ovs_flow_tbl_num_masks(const struct flow_table *table)
 	return READ_ONCE(ma->count);
 }
 
+u32 ovs_flow_tbl_masks_cache_size(const struct flow_table *table)
+{
+	struct mask_cache *mc = rcu_dereference(table->mask_cache);
+
+	return READ_ONCE(mc->cache_size);
+}
+
 static struct table_instance *table_instance_expand(struct table_instance *ti,
 						    bool ufid)
 {
diff --git a/net/openvswitch/flow_table.h b/net/openvswitch/flow_table.h
index 325e939371d8..f2dba952db2f 100644
--- a/net/openvswitch/flow_table.h
+++ b/net/openvswitch/flow_table.h
@@ -27,6 +27,12 @@ struct mask_cache_entry {
 	u32 mask_index;
 };
 
+struct mask_cache {
+	struct rcu_head rcu;
+	u32 cache_size;  /* Must be ^2 value. */
+	struct mask_cache_entry __percpu *mask_cache;
+};
+
 struct mask_count {
 	int index;
 	u64 counter;
@@ -53,7 +59,7 @@ struct table_instance {
 struct flow_table {
 	struct table_instance __rcu *ti;
 	struct table_instance __rcu *ufid_ti;
-	struct mask_cache_entry __percpu *mask_cache;
+	struct mask_cache __rcu *mask_cache;
 	struct mask_array __rcu *mask_array;
 	unsigned long last_rehash;
 	unsigned int count;
@@ -77,6 +83,8 @@ int ovs_flow_tbl_insert(struct flow_table *table, struct sw_flow *flow,
 			const struct sw_flow_mask *mask);
 void ovs_flow_tbl_remove(struct flow_table *table, struct sw_flow *flow);
 int  ovs_flow_tbl_num_masks(const struct flow_table *table);
+u32  ovs_flow_tbl_masks_cache_size(const struct flow_table *table);
+void ovs_flow_tbl_masks_cache_resize(struct flow_table *table, u32 size);
 struct sw_flow *ovs_flow_tbl_dump_next(struct table_instance *table,
 				       u32 *bucket, u32 *idx);
 struct sw_flow *ovs_flow_tbl_lookup_stats(struct flow_table *,