Re: [patch 2/2] QEMU: decrease console "refresh rate" with -nographic

Avi Kivity
2008-04-14T16:24:06Z

Marcelo Tosatti wrote:
> On Sun, Apr 13, 2008 at 06:30:34PM +0200, Anders wrote:
>
>> Marcelo Tosatti wrote:
>>
>>
>>> With SIGIO enabled on stdio, there's no need to wakeup the thread
>>> performing IO every 30ms.
>>>
>>> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
>>>
>>> Index: kvm-userspace.io/qemu/vl.c
>>> ===================================================================
>>> --- kvm-userspace.io.orig/qemu/vl.c
>>> +++ kvm-userspace.io/qemu/vl.c
>>> @@ -5640,6 +5640,7 @@ static void dumb_display_init(DisplaySta
>>> ds->dpy_update = dumb_update;
>>> ds->dpy_resize = dumb_resize;
>>> ds->dpy_refresh = dumb_refresh;
>>> + ds->gui_timer_interval = 1000;
>>> }
>>>
>>> /***********************************************************/
>>>
>>>
>> Why even the 1000ms timer? I was proposing to just set ds->dpy_refresh
>> to NULL for the dumb_display, but hit the qemu-devel dead-end.
>>
>> http://lists.gnu.org/archive/html/qemu-devel/2008-01/msg00374.html
>>
>> Do you see a problem with that approach?
>>
>
> Issue is that the dumb console timer "wakes up" the vcpu to do IO
> processing in main_loop_wait().
>
> So while you're right that vga_hw_update() is a no-op for the -nographic
> case, the indirect effect of the timer triggering main_loop_wait() is
> needed for reading input from stdio in a way that feels interactive for
> the user.
>
>

Why not enable SIGIO on stdio input, like the rest of the fd handling in
qemu?

--
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