[ovs-dev] [PATCH] ofproto: Optimise OpenFlow flow expiry

Simon Horman horms at verge.net.au
Tue Jan 15 04:20:57 UTC 2013


Optimise OpenFlow flow expiry by placing expirable flows on a list.
This optimises scanning of flows for expiry in two ways:

* Empirically list traversal appears faster than the code it replaces.

  With 1,000,000 flows present an otherwise idle system I observed CPU
  utilisation of around 20% with the existing code but around 10% with
  this new code.

* Flows that will never expire are not traversed.

  This addresses a case seen in the field.

Signed-off-by: Simon Horman <horms at verge.net.au>

---

v2
* As suggested by Ben Pfaff
  - Move implementation from classifier to ofproto layer
---
 ofproto/ofproto-dpif.c     |   12 +++---------
 ofproto/ofproto-provider.h |    8 ++++++++
 ofproto/ofproto.c          |    9 +++++++++
 3 files changed, 20 insertions(+), 9 deletions(-)

diff --git a/ofproto/ofproto-dpif.c b/ofproto/ofproto-dpif.c
index bc54122..87cd065 100644
--- a/ofproto/ofproto-dpif.c
+++ b/ofproto/ofproto-dpif.c
@@ -3725,8 +3725,7 @@ expire(struct dpif_backer *backer)
     update_stats(backer);
 
     HMAP_FOR_EACH (ofproto, all_ofproto_dpifs_node, &all_ofproto_dpifs) {
-        struct rule_dpif *rule, *next_rule;
-        struct oftable *table;
+        struct rule *rule, *next_rule;
         int dp_max_idle;
 
         if (ofproto->backer != backer) {
@@ -3741,13 +3740,8 @@ expire(struct dpif_backer *backer)
 
         /* Expire OpenFlow flows whose idle_timeout or hard_timeout
          * has passed. */
-        OFPROTO_FOR_EACH_TABLE (table, &ofproto->up) {
-            struct cls_cursor cursor;
-
-            cls_cursor_init(&cursor, &table->cls, NULL);
-            CLS_CURSOR_FOR_EACH_SAFE (rule, next_rule, up.cr, &cursor) {
-                rule_expire(rule);
-            }
+        LIST_FOR_EACH_SAFE(rule, next_rule, expirable, &ofproto->up.expirable) {
+            rule_expire(rule_dpif_cast(rule));
         }
 
         /* All outstanding data in existing flows has been accounted, so it's a
diff --git a/ofproto/ofproto-provider.h b/ofproto/ofproto-provider.h
index f2274ef..325bd5c 100644
--- a/ofproto/ofproto-provider.h
+++ b/ofproto/ofproto-provider.h
@@ -71,6 +71,10 @@ struct ofproto {
     struct oftable *tables;
     int n_tables;
 
+    /* Optimisation for flow expiry.
+     * These flows should all be present in tables */
+    struct list expirable;      /* List of expirable 'struct rule"s */
+
     /* OpenFlow connections. */
     struct connmgr *connmgr;
 
@@ -221,6 +225,10 @@ struct rule {
     enum nx_flow_monitor_flags monitor_flags;
     uint64_t add_seqno;         /* Sequence number when added. */
     uint64_t modify_seqno;      /* Sequence number when changed. */
+
+    /* Optimisation for flow expiry. */
+    struct list expirable;      /* Element of ofproto's expirable list
+                                 * if this rule is expirable */
 };
 
 static inline struct rule *
diff --git a/ofproto/ofproto.c b/ofproto/ofproto.c
index 8e2ea6b..375a1ca 100644
--- a/ofproto/ofproto.c
+++ b/ofproto/ofproto.c
@@ -419,6 +419,7 @@ ofproto_create(const char *datapath_name, const char *datapath_type,
     ofproto->max_ports = OFPP_MAX;
     ofproto->tables = NULL;
     ofproto->n_tables = 0;
+    list_init(&ofproto->expirable);
     ofproto->connmgr = connmgr_create(ofproto, datapath_name, datapath_name);
     ofproto->state = S_OPENFLOW;
     list_init(&ofproto->pending);
@@ -3166,6 +3167,7 @@ add_flow(struct ofproto *ofproto, struct ofconn *ofconn,
     rule->ofpacts_len = fm->ofpacts_len;
     rule->evictable = true;
     rule->eviction_group = NULL;
+    list_init(&rule->expirable);
     rule->monitor_flags = 0;
     rule->add_seqno = 0;
     rule->modify_seqno = 0;
@@ -4828,6 +4830,8 @@ oftable_remove_rule(struct rule *rule)
 
     classifier_remove(&table->cls, &rule->cr);
     eviction_group_remove_rule(rule);
+    if (!list_is_empty(&rule->expirable))
+        list_remove(&rule->expirable);
 }
 
 /* Inserts 'rule' into its oftable.  Removes any existing rule from 'rule''s
@@ -4839,6 +4843,11 @@ oftable_replace_rule(struct rule *rule)
     struct ofproto *ofproto = rule->ofproto;
     struct oftable *table = &ofproto->tables[rule->table_id];
     struct rule *victim;
+    bool may_expire = rule->hard_timeout || rule->idle_timeout;
+
+    if (may_expire) {
+        list_insert(&ofproto->expirable, &rule->expirable);
+    }
 
     victim = rule_from_cls_rule(classifier_replace(&table->cls, &rule->cr));
     if (victim) {
-- 
1.7.10.4




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