ofproto-dpif: Implement "flow setup governor" to speed up many short flows.

[sliver-openvswitch.git] / ofproto / ofproto-dpif-governor.h

diff --git a/ofproto/ofproto-dpif-governor.h b/ofproto/ofproto-dpif-governor.h
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+++ b/ofproto/ofproto-dpif-governor.h
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+/*
+ * Copyright (c) 2012 Nicira Networks.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef OFPROTO_DPIF_GOVERNOR_H
+#define OFPROTO_DPIF_GOVERNOR_H 1
+
+/* Flow setup rate limiter.
+ *
+ * A governor in an engine limits a vehicle's speed.  This governor limits the
+ * rate at which flows are set up in the datapath.  The client provides as
+ * input the hashes of observed packets.  The governor keeps track of hashes
+ * seen multiple times.  When a given hash is seen often enough, the governor
+ * indicates to its client that it should set up a facet and a subfacet and a
+ * datapath flow for that flow.
+ *
+ * The same tracking could be done in terms of facets and subfacets directly,
+ * but the governor code uses much less time and space to do the same job. */
+
+#include <stdbool.h>
+#include <stdint.h>
+
+struct governor {
+    char *name;                 /* Name, for log messages. */
+    uint8_t *table;             /* Table of counters, two per byte. */
+    unsigned int size;          /* Table size in bytes. */
+    long long int start;        /* Time when the table was last cleared. */
+    unsigned int n_packets;     /* Number of packets processed. */
+};
+
+struct governor *governor_create(const char *name);
+void governor_destroy(struct governor *);
+
+void governor_run(struct governor *);
+void governor_wait(struct governor *);
+
+bool governor_is_idle(struct governor *);
+
+bool governor_should_install_flow(struct governor *, uint32_t hash, int n);
+
+#endif /* ofproto/ofproto-dpif-governor.h */