Re: [pulseaudio-discuss] [PATCH] use CLOCK_MONOTONIC_COARSE to reduce the system call
在 2012年3月30日 下午12:48，Arun Raghavan arun.ragha...@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. ___ pulseaudio-discuss mailing list pulseaudio-discuss@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/pulseaudio-discuss
Re: [pulseaudio-discuss] [PATCH] use CLOCK_MONOTONIC_COARSE to reduce the system call
On 3/29/2012 8:31 AM, 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. Is this something desirable for PulseAudio? This could impact the timer-based scheduling, I'd rather keep the precision here. -Pierre ___ pulseaudio-discuss mailing list pulseaudio-discuss@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/pulseaudio-discuss
Re: [pulseaudio-discuss] [PATCH] use CLOCK_MONOTONIC_COARSE to reduce the system call
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. Cheers, Arun ___ pulseaudio-discuss mailing list pulseaudio-discuss@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/pulseaudio-discuss
