[Qemu-devel] [RFC 2/3] monitor: throttle QAPI_EVENT_VSERPORT_CHANGE by "id"

[marcandre.lureau@redhat.com]

From: Marc-André Lureau <marcandre.lureau@redhat.com>

Use a hash table to lookup the pending event corresponding to the "id"
field. The hash table may grow without limit here, the following patch
will add some cleaning.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
---
 monitor.c | 104 ++++++++++++++++++++++++++++++++++++++++++++++----------------
 1 file changed, 78 insertions(+), 26 deletions(-)

diff --git a/monitor.c b/monitor.c
index 9c51ffa..7334ffb 100644
--- a/monitor.c
+++ b/monitor.c
@@ -462,10 +462,10 @@ static void monitor_qapi_event_emit(QAPIEvent event, QObject *data)
 }
 
 static bool
-monitor_qapi_event_delay(MonitorQAPIEventState *evstate, QDict *data)
+monitor_qapi_event_pending_update(MonitorQAPIEventState *evstate,
+                                  MonitorQAPIEventPending *p, QDict *data)
 {
     int64_t now = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
-    MonitorQAPIEventPending *p = evstate->data;
     int64_t delta = now - p->last;
 
     /* Rate limit of 0 indicates no throttling */
@@ -494,31 +494,13 @@ monitor_qapi_event_delay(MonitorQAPIEventState *evstate, QDict *data)
     return FALSE;
 }
 
-/*
- * Queue a new event for emission to Monitor instances,
- * applying any rate limiting if required.
- */
-static void
-monitor_qapi_event_queue(QAPIEvent event, QDict *data, Error **errp)
-{
-    MonitorQAPIEventState *evstate;
-    assert(event < QAPI_EVENT_MAX);
-    int64_t now = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
-
-    evstate = &(monitor_qapi_event_state[event]);
-    trace_monitor_protocol_event_queue(event,
-                                       data,
-                                       evstate->rate,
-                                       now);
 
-    qemu_mutex_lock(&monitor_lock);
-
-    if (!evstate->delay ||
-        !evstate->delay(evstate, data)) {
-        monitor_qapi_event_emit(event, QOBJECT(data));
-    }
+static bool
+monitor_qapi_event_delay(MonitorQAPIEventState *evstate, QDict *data)
+{
+    MonitorQAPIEventPending *p = evstate->data;
 
-    qemu_mutex_unlock(&monitor_lock);
+    return monitor_qapi_event_pending_update(evstate, p, data);
 }
 
 /*
@@ -558,6 +540,58 @@ monitor_qapi_event_pending_new(QAPIEvent event)
     return p;
 }
 
+static bool
+monitor_qapi_event_id_delay(MonitorQAPIEventState *evstate, QDict *data)
+{
+    GHashTable *ht = evstate->data;
+    QDict *s = qdict_get_qdict(data, "data");
+    const char *id = qdict_get_str(s, "id");
+    MonitorQAPIEventPending *p = g_hash_table_lookup(ht, id);
+    QAPIEvent event = evstate - monitor_qapi_event_state;
+
+    if (!p) {
+        p = monitor_qapi_event_pending_new(event);
+        g_hash_table_insert(ht, g_strdup(id), p);
+    }
+
+    return monitor_qapi_event_pending_update(evstate, p, data);
+}
+
+/*
+ * Queue a new event for emission to Monitor instances,
+ * applying any rate limiting if required.
+ */
+static void
+monitor_qapi_event_queue(QAPIEvent event, QDict *data, Error **errp)
+{
+    MonitorQAPIEventState *evstate;
+    assert(event < QAPI_EVENT_MAX);
+    int64_t now = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
+
+    evstate = &(monitor_qapi_event_state[event]);
+    trace_monitor_protocol_event_queue(event,
+                                       data,
+                                       evstate->rate,
+                                       now);
+
+    qemu_mutex_lock(&monitor_lock);
+
+    if (!evstate->delay ||
+        !evstate->delay(evstate, data)) {
+        monitor_qapi_event_emit(event, QOBJECT(data));
+    }
+
+    qemu_mutex_unlock(&monitor_lock);
+}
+
+static void
+monitor_qapi_event_pending_free(MonitorQAPIEventPending *p)
+{
+    timer_del(p->timer);
+    timer_free(p->timer);
+    g_free(p);
+}
+
 /*
  * @event: the event ID to be limited
  * @rate: the rate limit in milliseconds
@@ -582,6 +616,24 @@ monitor_qapi_event_throttle(QAPIEvent event, int64_t rate)
     evstate->data = monitor_qapi_event_pending_new(event);
 }
 
+static void
+monitor_qapi_event_id_throttle(QAPIEvent event, int64_t rate)
+{
+    MonitorQAPIEventState *evstate;
+    assert(event < QAPI_EVENT_MAX);
+
+    evstate = &(monitor_qapi_event_state[event]);
+
+    trace_monitor_protocol_event_throttle(event, rate);
+    assert(rate * SCALE_MS <= INT64_MAX);
+    evstate->rate = rate * SCALE_MS;
+
+    evstate->delay = monitor_qapi_event_id_delay;
+    evstate->data =
+        g_hash_table_new_full(g_str_hash, g_str_equal, NULL,
+            (GDestroyNotify)monitor_qapi_event_pending_free);
+}
+
 static void monitor_qapi_event_init(void)
 {
     /* Limit guest-triggerable events to 1 per second */
@@ -590,7 +642,7 @@ static void monitor_qapi_event_init(void)
     monitor_qapi_event_throttle(QAPI_EVENT_BALLOON_CHANGE, 1000);
     monitor_qapi_event_throttle(QAPI_EVENT_QUORUM_REPORT_BAD, 1000);
     monitor_qapi_event_throttle(QAPI_EVENT_QUORUM_FAILURE, 1000);
-    monitor_qapi_event_throttle(QAPI_EVENT_VSERPORT_CHANGE, 1000);
+    monitor_qapi_event_id_throttle(QAPI_EVENT_VSERPORT_CHANGE, 1000);
 
     qmp_event_set_func_emit(monitor_qapi_event_queue);
 }
-- 
2.4.3