[pulseaudio-discuss] [PATCH] use CLOCK_MONOTONIC_COARSE to reduce the system call

rong deng dzrongg at gmail.com
Sat Mar 31 05:59:49 PDT 2012

在 2012年3月30日 下午12:48,Arun Raghavan <arun.raghavan at collabora.co.uk>写道:

> Hi,
> On Thu, 2012-03-29 at 21:31 +0800, Deng Zhenrong wrote:
> > According to the description below:
> >
> >         http://lkml.org/lkml/2009/7/17/258
> >
> > There are two benefits:
> > a) it doesn't need to access the hardware.
> > b) avoid the syscall by using vdso clock_gettime().
> >
> > The cons is the CLOCK_MONOTONIC_COARSE returns the time at the last
> > tick.
> As Pierre mentions, we actually _want_ high resolution time sources for
> our uses. We use these timers to predict when the audio buffer will be
> nearing being empty so that we can wake up and fill the buffer again.
> Having a coarse timer for this purpose would mean that we can be woken
> up late, causing the device to underrun and users to hear glitches.
Maybe I'm testing this patch in an idle state, so there's no underrun seen,
I'll take that into account.  Thanks for your clarification here. It helps
me understand pulseaudio better.
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