controller: ofctrl: Use index for meter lookups.

Currently, ovn-controller attempts to sync all the meters on each
ofctrl_put() call.  And the complexity of this logic is quadratic
because for each desired meter we perform a full scan of all the
rows in the Southbound Meter table in order to lookup a matching
meter.  This is very inefficient.  In a setup with 25K meters this
operation takes anywhere from 30 to 60 seconds to perform.  All
that time ovn-controller is blocked and doesn't process any updates.
So, addition of new ports in such a setup becomes very slow.

The meter lookup is performed by name and we have an index for it
in the database schema.  Might as well use it.

Using the index for lookup reduces complexity to O(n * log n).
And the time to process port addition on the same setup drops down
to just 100 - 300 ms.

We are still iterating over all the desired meters while they can
probably be processed incrementally instead.  But using an index
is a simpler fix for now.

Fixes: 885655e ("controller: reconfigure ovs meters for ovn meters")
Fixes: 999e1ad ("ovn: Support configuring meters through SB Meter table.")
Reported-at: https://issues.redhat.com/browse/FDP-399
Signed-off-by: Ilya Maximets <i.maximets@ovn.org>
Acked-by: Han Zhou <hzhou@ovn.org>
Signed-off-by: Mark Michelson <mmichels@redhat.com>

controller/ofctrl.c

@@ -2259,18 +2259,29 @@ ofctrl_meter_bands_erase(struct ovn_extend_table_info *entry,
     }
 }
 
+static const struct sbrec_meter *
+sb_meter_lookup_by_name(struct ovsdb_idl_index *sbrec_meter_by_name,
+                        const char *name)
+{
+    const struct sbrec_meter *sb_meter;
+    struct sbrec_meter *index_row;
+
+    index_row = sbrec_meter_index_init_row(sbrec_meter_by_name);
+    sbrec_meter_index_set_name(index_row, name);
+    sb_meter = sbrec_meter_index_find(sbrec_meter_by_name, index_row);
+    sbrec_meter_index_destroy_row(index_row);
+
+    return sb_meter;
+}
+
 static void
 ofctrl_meter_bands_sync(struct ovn_extend_table_info *m_existing,
-                        const struct sbrec_meter_table *meter_table,
+                        struct ovsdb_idl_index *sbrec_meter_by_name,
                         struct ovs_list *msgs)
 {
     const struct sbrec_meter *sb_meter;
-    SBREC_METER_TABLE_FOR_EACH (sb_meter, meter_table) {
-        if (!strcmp(m_existing->name, sb_meter->name)) {
-            break;
-        }
-    }
 
+    sb_meter = sb_meter_lookup_by_name(sbrec_meter_by_name, m_existing->name);
     if (sb_meter) {
         /* OFPMC13_ADD or OFPMC13_MODIFY */
         ofctrl_meter_bands_update(sb_meter, m_existing, msgs);
@@ -2282,16 +2293,12 @@ ofctrl_meter_bands_sync(struct ovn_extend_table_info *m_existing,
 
 static void
 add_meter(struct ovn_extend_table_info *m_desired,
-          const struct sbrec_meter_table *meter_table,
+          struct ovsdb_idl_index *sbrec_meter_by_name,
           struct ovs_list *msgs)
 {
     const struct sbrec_meter *sb_meter;
-    SBREC_METER_TABLE_FOR_EACH (sb_meter, meter_table) {
-        if (!strcmp(m_desired->name, sb_meter->name)) {
-            break;
-        }
-    }
 
+    sb_meter = sb_meter_lookup_by_name(sbrec_meter_by_name, m_desired->name);
     if (!sb_meter) {
         static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(5, 1);
         VLOG_ERR_RL(&rl, "could not find meter named \"%s\"", m_desired->name);
@@ -2658,7 +2665,7 @@ ofctrl_put(struct ovn_desired_flow_table *lflow_table,
            struct ovn_desired_flow_table *pflow_table,
            struct shash *pending_ct_zones,
            struct hmap *pending_lb_tuples,
-           const struct sbrec_meter_table *meter_table,
+           struct ovsdb_idl_index *sbrec_meter_by_name,
            uint64_t req_cfg,
            bool lflows_changed,
            bool pflows_changed)
@@ -2735,10 +2742,10 @@ ofctrl_put(struct ovn_desired_flow_table *lflow_table,
                  * describes the meter itself. */
                 add_meter_string(m_desired, &msgs);
             } else {
-                add_meter(m_desired, meter_table, &msgs);
+                add_meter(m_desired, sbrec_meter_by_name, &msgs);
             }
         } else {
-            ofctrl_meter_bands_sync(m_existing, meter_table, &msgs);
+            ofctrl_meter_bands_sync(m_existing, sbrec_meter_by_name, &msgs);
         }
     }
 

controller/ofctrl.h

@@ -59,7 +59,7 @@ void ofctrl_put(struct ovn_desired_flow_table *lflow_table,
                 struct ovn_desired_flow_table *pflow_table,
                 struct shash *pending_ct_zones,
                 struct hmap *pending_lb_tuples,
-                const struct sbrec_meter_table *,
+                struct ovsdb_idl_index *sbrec_meter_by_name,
                 uint64_t nb_cfg,
                 bool lflow_changed,
                 bool pflow_changed);

controller/ovn-controller.c

@@ -5102,6 +5102,8 @@ main(int argc, char *argv[])
         = chassis_private_index_create(ovnsb_idl_loop.idl);
     struct ovsdb_idl_index *sbrec_multicast_group_by_name_datapath
         = mcast_group_index_create(ovnsb_idl_loop.idl);
+    struct ovsdb_idl_index *sbrec_meter_by_name
+        = ovsdb_idl_index_create1(ovnsb_idl_loop.idl, &sbrec_meter_col_name);
     struct ovsdb_idl_index *sbrec_logical_flow_by_logical_datapath
         = ovsdb_idl_index_create1(ovnsb_idl_loop.idl,
                                   &sbrec_logical_flow_col_logical_datapath);
@@ -5917,7 +5919,7 @@ main(int argc, char *argv[])
                                    &pflow_output_data->flow_table,
                                    &ct_zones_data->pending,
                                    &lb_data->removed_tuples,
-                                   sbrec_meter_table_get(ovnsb_idl_loop.idl),
+                                   sbrec_meter_by_name,
                                    ofctrl_seqno_get_req_cfg(),
                                    engine_node_changed(&en_lflow_output),
                                    engine_node_changed(&en_pflow_output));