On 2012-09-19 09:26, Paolo Bonzini wrote:
> 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 <pbonz...@redhat.com>
>> Cc: Jan Kiszka <jan.kis...@siemens.com>
>> Signed-off-by: Anthony Liguori <aligu...@us.ibm.com>
>> ---
>> 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.
What would be the advantage of timerfd over select? On Linux, both use
hrtimers (and low slack for RT processes). I'm starting to like the
select/WaitForMultipleObjects pattern as it would allow to consolidate
over basically two versions of timers and simplify the code.
Jan
>
> 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
>
--
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