bus: track the number of monitors

If no monitors are installed (the expected case), skip driver_monitor() which is moderately expensive and otherwise would be performed on every message, even if it ends up being a noop. Signed-off-by: Tom Gundersen <[email protected]>
bus1 · Jan 29, 2018 · dee3380 · dee3380
1 parent 7692572
commit dee3380
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Showing 4 changed files with 17 additions and 0 deletions.
diff --git a/src/bus/bus.h b/src/bus/bus.h
@@ -39,6 +39,7 @@ struct Bus {
         MatchRegistry sender_matches;
         PeerRegistry peers;
 
+        uint64_t n_monitors;
         uint64_t transaction_ids;
         uint64_t listener_ids;
 

diff --git a/src/bus/driver.c b/src/bus/driver.c
@@ -320,6 +320,9 @@ static int driver_monitor(Bus *bus, Peer *sender, Message *message) {
         NameOwnership *ownership;
         int r;
 
+        if (!bus->n_monitors)
+                return 0;
+
         filter.type = message->metadata.header.type;
         filter.sender = sender ? sender->id : ADDRESS_ID_INVALID;
         filter.interface = message->metadata.fields.interface;
@@ -1789,6 +1792,8 @@ int driver_goodbye(Peer *peer, bool silent) {
                                 return error_trace(r);
                 }
                 peer_unregister(peer);
+        } else if (peer_is_monitor(peer)) {
+                peer_stop_monitor(peer);
         }
 
         c_list_for_each_entry_safe(rule, rule_safe, &peer->name_owner_changed_matches.rule_list, registry_link)

diff --git a/src/bus/peer.c b/src/bus/peer.c
@@ -575,10 +575,20 @@ int peer_become_monitor(Peer *peer, MatchOwner *owned_matches) {
                 return poison;
 
         peer->monitor = true;
+        ++peer->bus->n_monitors;
 
         return 0;
 }
 
+void peer_stop_monitor(Peer *peer) {
+        assert(!peer->registered);
+        assert(peer->monitor);
+        assert(c_rbtree_is_empty(&peer->owned_matches.rule_tree));
+
+        peer->monitor = false;
+        --peer->bus->n_monitors;
+}
+
 void peer_flush_matches(Peer *peer) {
         CRBNode *node;
 

diff --git a/src/bus/peer.h b/src/bus/peer.h
@@ -119,6 +119,7 @@ void peer_release_name_ownership(Peer *peer, NameOwnership *ownership, NameChang
 int peer_add_match(Peer *peer, const char *rule_string);
 int peer_remove_match(Peer *peer, const char *rule_string);
 int peer_become_monitor(Peer *peer, MatchOwner *owner);
+void peer_stop_monitor(Peer *peer);
 void peer_flush_matches(Peer *peer);
 
 int peer_queue_call(PolicySnapshot *sender_policy, NameSet *sender_names, MatchRegistry *sender_matches, ReplyOwner *sender_replies, User *sender_user, uint64_t sender_id, Peer *receiver, Message *message);