classifier: Optimize search of "catchall" table.

Most flow tables have some kind of "catchall" rule that matches every
packet.  For this table, the cost of copying, zeroing, and hashing the
input flow is significant.  This patch avoids these costs.

Signed-off-by: Ben Pfaff <blp@nicira.com>

diff --git a/lib/classifier.c b/lib/classifier.c
index b6c477a0babef28622c159c2164f192ce1084b85..122a6c6e9e6d01901cb615edac3d215504a2c162 100644 (file)
--- a/lib/classifier.c
+++ b/lib/classifier.c
@@ -1036,6 +1036,7 @@ insert_table(struct classifier *cls, const struct flow_wildcards *wc)
     table = xzalloc(sizeof *table);
     hmap_init(&table->rules);
     table->wc = *wc;
+    table->is_catchall = flow_wildcards_is_catchall(&table->wc);
     hmap_insert(&cls->tables, &table->hmap_node, flow_wildcards_hash(wc, 0));
 
     return table;
@@ -1053,16 +1054,24 @@ static struct cls_rule *
 find_match(const struct cls_table *table, const struct flow *flow)
 {
     struct cls_rule *rule;
-    struct flow f;
 
-    f = *flow;
-    flow_zero_wildcards(&f, &table->wc);
-    HMAP_FOR_EACH_WITH_HASH (rule, hmap_node, flow_hash(&f, 0),
-                             &table->rules) {
-        if (flow_equal(&f, &rule->flow)) {
+    if (table->is_catchall) {
+        HMAP_FOR_EACH (rule, hmap_node, &table->rules) {
             return rule;
         }
+    } else {
+        struct flow f;
+
+        f = *flow;
+        flow_zero_wildcards(&f, &table->wc);
+        HMAP_FOR_EACH_WITH_HASH (rule, hmap_node, flow_hash(&f, 0),
+                                 &table->rules) {
+            if (flow_equal(&f, &rule->flow)) {
+                return rule;
+            }
+        }
     }
+
     return NULL;
 }
 

diff --git a/lib/classifier.h b/lib/classifier.h
index f9bcabbef6d08a75283347c504a6f55f42fd7b97..84cb6028d24262eb0bdee13edd299f0214d110b6 100644 (file)
--- a/lib/classifier.h
+++ b/lib/classifier.h
@@ -48,6 +48,7 @@ struct cls_table {
     struct hmap rules;          /* Contains "struct cls_rule"s. */
     struct flow_wildcards wc;   /* Wildcards for fields. */
     int n_table_rules;          /* Number of rules, including duplicates. */
+    bool is_catchall;           /* True if this table wildcards every field. */
 };
 
 /* Returns true if 'table' is a "catch-all" table that will match every
@@ -55,11 +56,7 @@ struct cls_table {
 static inline bool
 cls_table_is_catchall(const struct cls_table *table)
 {
-    /* A catch-all table can only have one rule, so use hmap_count() as a cheap
-     * check to rule out other kinds of match before doing the full check with
-     * flow_wildcards_is_catchall(). */
-    return (hmap_count(&table->rules) == 1
-            && flow_wildcards_is_catchall(&table->wc));
+    return table->is_catchall;
 }
 
 /* A flow classification rule.