ui/spice: Add an option to submit gl_draw requests at fixed rate

In the specific case where the display layer (virtio-gpu) is using
dmabuf, and if remote clients are enabled (-spice gl=on,port=xxxx),
it makes sense to limit the maximum (streaming) rate (refresh rate)
to a fixed value using the GUI refresh timer. Otherwise, the updates
or gl_draw requests would be sent as soon as the Guest submits a new
frame which is not optimal as it would lead to increased network
traffic and wastage of GPU cycles if the frames get dropped.

Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Marc-André Lureau <marcandre.lureau@redhat.com>
Cc: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Cc: Frediano Ziglio <freddy77@gmail.com>
Cc: Dongwon Kim <dongwon.kim@intel.com>
Cc: Michael Scherle <michael.scherle@rz.uni-freiburg.de>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: Vivek Kasireddy <vivek.kasireddy@intel.com>
Message-Id: <20250617043546.1022779-5-vivek.kasireddy@intel.com>

1 files changed, 12 insertions, 0 deletions

diff --git a/ui/spice-core.c b/ui/spice-core.c
index 51bdcef1af..5992f9daec 100644
--- a/ui/spice-core.c
+++ b/ui/spice-core.c
@@ -56,6 +56,8 @@ struct SpiceTimer {
     QEMUTimer *timer;
 };
 
+#define DEFAULT_MAX_REFRESH_RATE 30
+
 static SpiceTimer *timer_add(SpiceTimerFunc func, void *opaque)
 {
     SpiceTimer *timer;
@@ -492,6 +494,9 @@ static QemuOptsList qemu_spice_opts = {
             .name = "video-codec",
             .type = QEMU_OPT_STRING,
         },{
+            .name = "max-refresh-rate",
+            .type = QEMU_OPT_NUMBER,
+        },{
             .name = "agent-mouse",
             .type = QEMU_OPT_BOOL,
         },{
@@ -804,6 +809,13 @@ static void qemu_spice_init(void)
         spice_server_set_streaming_video(spice_server, SPICE_STREAM_VIDEO_OFF);
     }
 
+    spice_max_refresh_rate = qemu_opt_get_number(opts, "max-refresh-rate",
+                                                 DEFAULT_MAX_REFRESH_RATE);
+    if (spice_max_refresh_rate <= 0) {
+        error_report("max refresh rate/fps is invalid");
+        exit(1);
+    }
+
     spice_server_set_agent_mouse
         (spice_server, qemu_opt_get_bool(opts, "agent-mouse", 1));
     spice_server_set_playback_compression