Re: [Qemu-devel] [PATCH 1/2] audio: honor QEMU_AUDIO_TIMER_PERIOD instead of waking up every *nano* second

[Hans de Goede]

Hi,

On 10/10/2013 08:31 AM, Alex Bligh wrote:
> On 9 Oct 2013, at 20:42, Hans de Goede wrote:
>
> > Now that we no longer have MIN_REARM_TIMER_NS a bug in the audio subsys has
> > clearly shown it self by trying to make a timer fire every nano second.
> >
> > Note we have a similar problem in 1.6, 1.5 and older but there
> > MIN_REARM_TIMER_NS limits the wakeups caused by audio being active to
> > 4000 times / second. This still causes a host cpu load of 50 % for simply
> > playing audio, where as with this patch git master is at 13%, so we should
> > backport this to 1.5 and 1.6 too.
> >
> > Note this will not apply to 1.5 and 1.6 as is.
> >
> > Cc: address@hidden
> > Signed-off-by: Hans de Goede <address@hidden>
> > ---
> > audio/audio.c | 3 ++-
> > 1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/audio/audio.c b/audio/audio.c
> > index af4cdf6..b3db679 100644
> > --- a/audio/audio.c
> > +++ b/audio/audio.c
> > @@ -1124,7 +1124,8 @@ static int audio_is_timer_needed (void)
> > static void audio_reset_timer (AudioState *s)
> > {
> >      if (audio_is_timer_needed ()) {
> > -        timer_mod (s->ts, qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) + 1);
> > +        timer_mod (s->ts,
> > +            qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) + conf.period.ticks);
>
> This assumes conf.period.ticks is in nanoseconds. That seems wrong.
> Suggest multiplying by SCALE_US or SCALE_MS.

Which it is, quoting from higher up in the same file:

        conf.period.ticks =
            muldiv64 (1, get_ticks_per_sec (), conf.period.hertz);

And get_ticks_per_sec () returns ns .

Regards,

Hans



> Alex
>
> >      }
> >      else {
> >          timer_del (s->ts);
> > --
> > 1.8.3.1