ui/dbus: filter out pending messages when scanout

The "Listener" connection, being private and under the control of the
qemu display, allows for the optimization of discarding pending
intermediary messages when queuing a new scanout. This ensures that the
client receives only the latest scanout update, improving communication
efficiency.

While the current implementation does not provide a mechanism for
clients who may wish to receive all updates, making this behavior
optional could be considered in the future. For now, adopting this new
default behavior accelerates the communication process without a
guarantee of delivering all updates.

The filter is removed when the connection is dropped.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>

diff --git a/ui/dbus-listener.c b/ui/dbus-listener.c
index 3f4529dbbd1ea0e7aca3cba8758cc63058292f01..4a0a5d78f937096d2f6fa09141aa3f47e95736ff 100644 (file)
--- a/ui/dbus-listener.c
+++ b/ui/dbus-listener.c
@@ -83,6 +83,9 @@ struct _DBusDisplayListener {
     egl_fb fb;
 #endif
 #endif
+
+    guint dbus_filter;
+    guint32 out_serial_to_discard;
 };
 
 G_DEFINE_TYPE(DBusDisplayListener, dbus_display_listener, G_TYPE_OBJECT)
@@ -90,6 +93,12 @@ G_DEFINE_TYPE(DBusDisplayListener, dbus_display_listener, G_TYPE_OBJECT)
 static void dbus_gfx_update(DisplayChangeListener *dcl,
                             int x, int y, int w, int h);
 
+static void ddl_discard_pending_messages(DBusDisplayListener *ddl)
+{
+    ddl->out_serial_to_discard = g_dbus_connection_get_last_serial(
+        g_dbus_proxy_get_connection(G_DBUS_PROXY(ddl->proxy)));
+}
+
 #ifdef CONFIG_OPENGL
 static void dbus_scanout_disable(DisplayChangeListener *dcl)
 {
@@ -276,6 +285,8 @@ static void dbus_scanout_dmabuf(DisplayChangeListener *dcl,
         return;
     }
 
+    ddl_discard_pending_messages(ddl);
+
     /* FIXME: add missing x/y/w/h support */
     qemu_dbus_display1_listener_call_scanout_dmabuf(
         ddl->proxy,
@@ -323,6 +334,8 @@ static bool dbus_scanout_map(DBusDisplayListener *ddl)
         return false;
     }
 
+    ddl_discard_pending_messages(ddl);
+
     if (!qemu_dbus_display1_listener_win32_map_call_scanout_map_sync(
             ddl->map_proxy,
             GPOINTER_TO_UINT(target_handle),
@@ -384,6 +397,8 @@ dbus_scanout_share_d3d_texture(
         return false;
     }
 
+    ddl_discard_pending_messages(ddl);
+
     qemu_dbus_display1_listener_win32_d3d11_call_scanout_texture2d(
         ddl->d3d11_proxy,
         GPOINTER_TO_INT(target_handle),
@@ -639,6 +654,8 @@ static void ddl_scanout(DBusDisplayListener *ddl)
         surface_stride(ddl->ds) * surface_height(ddl->ds), TRUE,
         (GDestroyNotify)pixman_image_unref, pixman_image_ref(ddl->ds->image));
 
+    ddl_discard_pending_messages(ddl);
+
     qemu_dbus_display1_listener_call_scanout(
         ddl->proxy, surface_width(ddl->ds), surface_height(ddl->ds),
         surface_stride(ddl->ds), surface_format(ddl->ds), v_data,
@@ -963,6 +980,28 @@ dbus_display_listener_setup_shared_map(DBusDisplayListener *ddl)
 #endif
 }
 
+static GDBusMessage *
+dbus_filter(GDBusConnection *connection,
+            GDBusMessage    *message,
+            gboolean         incoming,
+            gpointer         user_data)
+{
+    DBusDisplayListener *ddl = DBUS_DISPLAY_LISTENER(user_data);
+    guint32 serial;
+
+    if (incoming) {
+        return message;
+    }
+
+    serial = g_dbus_message_get_serial(message);
+    if (serial <= ddl->out_serial_to_discard) {
+        trace_dbus_filter(serial, ddl->out_serial_to_discard);
+        return NULL;
+    }
+
+    return message;
+}
+
 DBusDisplayListener *
 dbus_display_listener_new(const char *bus_name,
                           GDBusConnection *conn,
@@ -987,6 +1026,7 @@ dbus_display_listener_new(const char *bus_name,
         return NULL;
     }
 
+    ddl->dbus_filter = g_dbus_connection_add_filter(conn, dbus_filter, g_object_ref(ddl), g_object_unref);
     ddl->bus_name = g_strdup(bus_name);
     ddl->conn = conn;
     ddl->console = console;

diff --git a/ui/trace-events b/ui/trace-events
index 16c35c9fd6f09b54dfce2f40a7c42a06bc5c4c33..e6a28943036eb05cf9b17dd718fe73c3cf96a5e2 100644 (file)
--- a/ui/trace-events
+++ b/ui/trace-events
@@ -161,6 +161,7 @@ dbus_clipboard_register(const char *bus_name) "peer %s"
 dbus_clipboard_unregister(const char *bus_name) "peer %s"
 dbus_scanout_texture(uint32_t tex_id, bool backing_y_0_top, uint32_t backing_width, uint32_t backing_height, uint32_t x, uint32_t y, uint32_t w, uint32_t h) "tex_id:%u y0top:%d back:%ux%u %u+%u-%ux%u"
 dbus_gl_gfx_switch(void *p) "surf: %p"
+dbus_filter(unsigned int serial, unsigned int filter) "serial=%u (<= %u)"
 
 # egl-helpers.c
 egl_init_d3d11_device(void *p) "d3d device: %p"