[LAU] System Configuration: kernel, CPU frequency, hardware timers

[Len Ovens]

On Tue, 28 Aug 2018, Ralf Mardorf wrote:

> Regarding Ubuntu (at least for Xenial) there indeed is 'ondemand' in
> /etc/rc.d/, /etc/init.d/. However, I stay with 'powersave' or 'ondemand'

Not any more. It is there until 16.04 at least but vanishes at least by 
18.04 to be replaced by /lib/systemd/system/ondemand.service which calls 
/lib/systemd/set-cpufreq. The name ondemand is, as you say, misleading 
and powersave even more so. where powersave used to be "run at lowest 
speed" it is now what ondemand was supposed to be, but handled by the cpu 
itself. ondemand, I have read, uses more power than performance, but 
powersave works correctly. my cpu temp is higher at idle in performance 
than powersave... I don't have anything old enough to test ondemand with. 
In anycase, ondemand.service sets powersave in my case.

Installing cpufrequtils and setting it to set performance at boot no 
longer works as I said due to kernel modules missing at the time it runs 
at boot.

Using a utility to change cpu govering on the fly according to use does 
make sense.

For many people using usb devices at 128/2 or higher, this probably 
doesn't matter, but I like to make things work as well as possible at 16/2 
so that at higher latency I don;t get surprised... but most usb devices 
don't work that low. (USB clock is 1ms so probably 32/2 is lowest).

USB is not a gift for low latency audio, but a great boon for Linix 
compatablility.

--
Len Ovens
www.ovenwerks.net