Re: [Qemu-devel] [PATCH] qemu-clock: add an alarm timer based on timerfd

[Stefan Weil]

Am 19.09.2012 09:26, schrieb Paolo Bonzini:
> Il 18/09/2012 22:37, Anthony Liguori ha scritto:
> > Unfortunately, there's a lot of Windows code in qemu-timer.c and main-loop.c
> > right now otherwise the refactoring would be trivial.  I'll leave that for
> > another day.
> >
> > Cc: Paolo Bonzini <address@hidden>
> > Cc: Jan Kiszka <address@hidden>
> > Signed-off-by: Anthony Liguori <address@hidden>
> > ---
> > Please note, this is lightly tested.  Since this is such a fundamental change,
> > I'd like to do some performance analysis before committing but wanted to share
> > early.
> Looks good.  I think Peter Portante tested something similar, and found no big
> difference between the two.  But it's a good thing and, in my opinion, for
> non-timerfd OSes we should simply adjust the select() timeout and not bother
> with signals.
>
> I'm not sure if the same can be done for Windows, but I think it's possible as 
> long
> as you keep the timeBeginPeriod/timeEndPeriod calls.  As a start, Stefan, can 
> you
> check if the win32 timer works for you with the calls added?  Like this:
>
> diff --git a/qemu-timer.c b/qemu-timer.c
> index c7a1551..721c769 100644
> --- a/qemu-timer.c
> +++ b/qemu-timer.c
> @@ -673,6 +673,10 @@ static int win32_start_timer(struct qemu_alarm_timer *t)
>       HANDLE hTimer;
>       BOOLEAN success;
>   
> +    timeGetDevCaps(&mm_tc, sizeof(mm_tc));
> +
> +    timeBeginPeriod(mm_tc.wPeriodMin);
> +
>       /* If you call ChangeTimerQueueTimer on a one-shot timer (its period
>          is zero) that has already expired, the timer is not updated.  Since
>          creating a new timer is relatively expensive, set a bogus one-hour
> @@ -688,6 +692,7 @@ static int win32_start_timer(struct qemu_alarm_timer *t)
>       if (!success) {
>           fprintf(stderr, "Failed to initialize win32 alarm timer: %ld\n",
>                   GetLastError());
> +        timeEndPeriod(mm_tc.wPeriodMin);
>           return -1;
>       }
>   
> @@ -702,6 +707,7 @@ static void win32_stop_timer(struct qemu_alarm_timer *t)
>       if (hTimer) {
>           DeleteTimerQueueTimer(NULL, hTimer, NULL);
>       }
> +    timeEndPeriod(mm_tc.wPeriodMin);
>   }
>   
>   static void win32_rearm_timer(struct qemu_alarm_timer *t,
>
> Paolo

The win32 timer still works when these modifications were applied.
What are they good for?

Stefan