ovn-controller: Handle addresses addition in address set incrementally.

To avoid reprocessing the lflow when a referenced address set has new
addresses added, this patch generates a fake address set that only
contains the added addresses for flow generation, and then eliminates
the flows that are not related to the newly added addresses.

Scale test shows obvious performance gains because the time complexity
changed from O(n) to O(1). The bigger the size of address set, the more
CPU savings. With the AS size of 10k, the test shows ~40x speed up.

Test setup:
CPU: Intel(R) Core(TM) i9-7920X CPU @ 2.90GHz.
5 ACL all referencing an address set of 10,000 IPs.

Measure the time spent by ovn-controller for handling one IP
addition from the address set.

Before: ~400ms
After: 11-12ms

Signed-off-by: Han Zhou <hzhou@ovn.org>
Acked-by: Mark Michelson <mmichels@redhat.com>
Acked-by: Numan Siddique <numans@ovn.org>

controller/lflow-conj-ids.c

@@ -55,6 +55,9 @@ static void lflow_conj_ids_insert_(struct conj_ids *,
                                    const struct uuid *lflow_uuid,
                                    const struct uuid *dp_uuid,
                                    uint32_t start_conj_id, uint32_t n_conjs);
+static struct lflow_conj_node *
+lflow_conj_ids_find_(struct conj_ids *conj_ids, const struct uuid *lflow_uuid,
+                     const struct uuid *dp_uuid);
 static void lflow_conj_ids_free_(struct conj_ids *, struct lflow_conj_node *);
 static void lflow_conj_ids_free_for_lflow_dp(struct conj_ids *,
                                              const struct uuid *lflow_uuid,
@@ -197,6 +200,18 @@ lflow_conj_ids_alloc_specified(struct conj_ids *conj_ids,
     return true;
 }
 
+/* Find and return the start id that is allocated to the logical flow for the
+ * dp_uuid. Return 0 if not found. */
+uint32_t
+lflow_conj_ids_find(struct conj_ids *conj_ids, const struct uuid *lflow_uuid,
+                    const struct uuid *dp_uuid)
+{
+    struct lflow_conj_node *lflow_conj = lflow_conj_ids_find_(conj_ids,
+                                                              lflow_uuid,
+                                                              dp_uuid);
+    return lflow_conj ? lflow_conj->start_conj_id : 0;
+}
+
 /* Frees the conjunction IDs used by lflow_uuid. */
 void
 lflow_conj_ids_free(struct conj_ids *conj_ids, const struct uuid *lflow_uuid)

controller/lflow-conj-ids.h

@@ -39,6 +39,8 @@ bool lflow_conj_ids_alloc_specified(struct conj_ids *,
                                     const struct uuid *dp_uuid,
                                     uint32_t start_conj_id, uint32_t n_conjs);
 void lflow_conj_ids_free(struct conj_ids *, const struct uuid *lflow_uuid);
+uint32_t lflow_conj_ids_find(struct conj_ids *, const struct uuid *lflow_uuid,
+                             const struct uuid *dp_uuid);
 void lflow_conj_ids_init(struct conj_ids *);
 void lflow_conj_ids_destroy(struct conj_ids *);
 void lflow_conj_ids_clear(struct conj_ids *);