[LAD] discussing HZ (kernel timer frequency) and midi timing

[Florian Schmidt]

On Friday 04 May 2007, Mulyadi Santosa wrote:
> Hi
>
> Sorry for late reply..
>
> > I have
> > dev.rtc.max-user-freq = 8192
> > in my sysctl.conf.
> > Before seq24 timing seemed to be changing between laid back and forward.
> > Haven't tested since setting.
> > Do
> > cat /proc/sys/dev/rtc/max-user-freq
> > to see your setting now.
> > echo 8192 > /proc/sys/dev/rtc/max-user-freq
> > changes setting.
>
> Thank you, even this small hint gave me a valuable direction. It makes
> me believe there are many applications that do rely on non-kernel-timer
> source.. in this case RTC.
>
> May I ask, could seq24 reports somekind of note playing delay? or xruns?


seq24 does _not_ use RTC for timing. It uses an approach based on sleep() (in 
some way or the other), so setting the rtc-max-frequency does nothing for 
seq24 performance. To improve seq24 performance over the vanilla kernel you 
need a kernel with the system timer frequency set back to something like 
1000Hz (vanilla has 200Hz, which is too unprecise for MIDI timing based on 
sleeping short amounts of time)..

Flo




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