Re: [Qemu-devel] [PATCH] gtk: sync guest display updates to host display refresh

[Chen Zhang]

Additionally, the aforementioned patch performs OK for non-vfio OpenGL enabled 
GTK displays, and fails DMA Buf iGVT-g display only, so far as I could tell.

Perhaps a change like the following is better?

 static gboolean gd_frame_tick(GtkWidget *widget,
                               GdkFrameClock *frame_clock,
                               gpointer opaque)
 {
     VirtualConsole *vc = opaque;
-
-    vc->gfx.dcl.ops->dpy_refresh(&vc->gfx.dcl);
+    gint64 interval;
+    gdk_frame_clock_get_refresh_info(frame_clock,
+            0,
+            &interval,
+            NULL);
+    interval /= 1000;
+    if (vc->gfx.dcl.update_interval != interval) {
+        update_displaychangelistener(&vc->gfx.dcl, interval);
+    }
     return G_SOURCE_CONTINUE;
 }


> On Nov 14, 2018, at 11:10 AM, Chen Zhang <address@hidden> wrote:
> 
> Hi,
> 
> I have briefly tested this patch. Unfortunately, it apparently caused 
> deteriorated performance on a previously working Windows 10 guest with DMA 
> Buf.
> 
> The patched qemu not only clogged up graphics drawing, but also obstructed 
> the guest OS. The boot time and latency for guest operations (e.g. clicking 
> Start menu in guest) dramatically increased. My best guess would be that GTK 
> update events messed up with some polling in main_loop_wait(false), leading 
> to blocked IO, or conversely the GUI being blocked by IO.
> 
> Best regards,
> 
> --
> P.S:
> 
> The arguments for qemu:
> 
> /tmp/qemu-system-x86_64 -nodefaults -machine 
> pc,accel=kvm,usb=off,kernel_irqchip=on \
>  -vga none -display gtk,gl=on  -rtc base=localtime \
>  -device 
> vfio-pci,sysfsdev=/sys/bus/pci/devices/0000:00:02.0/{UUID-FOR-MDEV},x-igd-opregion=on,display=on,rombar=0
>  \
>  -m 3000 -realtime mlock=off -smp 3,sockets=1,cores=1 \
>  -drive file=/home/user/disk.img,format=qcow2,media=disk,if=ide \
>  -usb -device qemu-xhci,id=xhci -device usb-tablet,bus=xhci.0 \
>  -cpu host -monitor stdio
> 
> The host runs a Ubuntu 18.04 desktop.
> 
>> On Nov 13, 2018, at 5:02 PM, Gerd Hoffmann <address@hidden> wrote:
>> 
>> Reduce console refresh timer to idle refresh rate.  Register a frame
>> tick callback (called by gtk on each display frame) and use that to kick
>> display updates instead.
>> 
>> That should sync qemu refresh rate to display refresh rate.  It'll also
>> stop updating the qemu display in case the qemu is not visible (gtk
>> stops calling the frame tick callback then).
>> 
>> Buglink: https://bugs.launchpad.net/bugs/1802915
>> Suggested-by: Chen Zhang <address@hidden>
>> Signed-off-by: Gerd Hoffmann <address@hidden>
>> ---
>> ui/gtk.c | 16 ++++++++++++++++
>> 1 file changed, 16 insertions(+)
>> 
>> diff --git a/ui/gtk.c b/ui/gtk.c
>> index 579990b865..8f79dfe42c 100644
>> --- a/ui/gtk.c
>> +++ b/ui/gtk.c
>> @@ -1661,6 +1661,16 @@ static gboolean gd_configure(GtkWidget *widget,
>>    return FALSE;
>> }
>> 
>> +static gboolean gd_frame_tick(GtkWidget *widget,
>> +                              GdkFrameClock *frame_clock,
>> +                              gpointer opaque)
>> +{
>> +    VirtualConsole *vc = opaque;
>> +
>> +    vc->gfx.dcl.ops->dpy_refresh(&vc->gfx.dcl);
>> +    return G_SOURCE_CONTINUE;
>> +}
>> +
>> /** Virtual Console Callbacks **/
>> 
>> static GSList *gd_vc_menu_init(GtkDisplayState *s, VirtualConsole *vc,
>> @@ -1911,6 +1921,12 @@ static void gd_connect_vc_gfx_signals(VirtualConsole 
>> *vc)
>>                         G_CALLBACK(gd_focus_out_event), vc);
>>        g_signal_connect(vc->gfx.drawing_area, "configure-event",
>>                         G_CALLBACK(gd_configure), vc);
>> +        if (1 /* make that a config option ??? */) {
>> +            update_displaychangelistener(&vc->gfx.dcl,
>> +                                         GUI_REFRESH_INTERVAL_IDLE);
>> +            gtk_widget_add_tick_callback(vc->gfx.drawing_area,
>> +                                         gd_frame_tick, vc, NULL);
>> +        }
>>    } else {
>>        g_signal_connect(vc->gfx.drawing_area, "key-press-event",
>>                         G_CALLBACK(gd_text_key_down), vc);
>> -- 
>> 2.9.3
>> 
>