Kernel hertz rate and system clock

[sossego]

http://freebsd.mercurysquad.com/

kern.clockrate: { hz = 2000, tick = 500, profhz = 8126, stathz = 127 }

A value of 2500 or greater causes a skew of +1 and greater.
http://lists.freebsd.org/pipermail/freebsd-current/2011-February/023004.html
http://lists.freebsd.org/pipermail/freebsd-ipfw/2010-June/004261.html
https://groups.google.com/forum/#!topic/mailing.freebsd.ipfw/oVbFsI3JqfM
http://unix.derkeiler.com/Mailing-Lists/FreeBSD/net/2008-07/msg00094.html
http://unix.derkeiler.com/Mailing-Lists/FreeBSD/questions/2011-11/msg00616.html
http://unix.derkeiler.com/Mailing-Lists/FreeBSD/stable/2010-09/msg00632.html

 

[xibo]

Is there any gain in increasing kern.hz over 1000 to begin with?

 

[sossego]

Latency decrease in audio effects and production. Of course, this may prove different when I can purchase a sound card with dedicated chips and memory.

 

[oops]

Audio device polling is disabled by default. You'd have better response time just by tuning hw.snd.latency and hw.snd.latency_profile using sysctl(8) or teaching the application to use SNDCTL_DSP_POLICY or SNDCTL_DSP_SETFRAGMENT on a modern (mostly tickless) FreeBSD kernel.

 

[sossego]

To what value when it is set to 5?

 

[oops]

The lowest possible and then increase by one until you stop hearing noise from buffer underrun. Alternatively, fix applications to cope better with small fragment size.

For example, with multimedia/mpv to reduce silence after resume from pause I use

# 4x interrupt rate (systat -v 1)
hw.snd.latency=4
hw.snd.latency_profile=0