[Qemu-devel] Re: Extremely slow graphic updates

[Stefano Stabellini <stefano.stabellini@eu.citrix.com>]

Lennart Sorensen wrote:

> I was trying to come up with a simple test case to show the problem,
> but found another one.  If I simply run qemu-system-ppc -vnc :1 I get
> nothing on VNC.  Using -sdl I get the openbios prompt.  If I use both
> -vnc :1 and -sdl I get openbios showing on both.  vnc by itself seems to
> only start displaying something once something other than openbios is
> running, like the bootloader or linux kernel.  That doesn't seem right.



I could reproduce this issue.
The problem seems to be strictly related to the gui_timer:

Currently we set the gui_timer only if someone implements dpy_refresh.
Since sdl implements dpy_refresh while vnc does not, when only vnc is
enabled the gui_timer is never allocated.

The weird thing is that even if I change the gui_update function to be
something like:

static void gui_update(void *opaque)
{
     uint64_t interval = GUI_REFRESH_INTERVAL;
     DisplayState *ds = opaque;
     DisplayChangeListener *dcl = ds->listeners;

     qemu_mod_timer(ds->gui_timer, interval + qemu_get_clock(rt_clock));
}

Vnc still works correctly.
So it doesn't matter the actual implementation of the function to be
called, as long as it is called.