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

On Mon, 27 Aug 2018, Kevin Cosgrove wrote:

> #   | sudo tee /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor
> sudo touch /etc/rc.d/rc.local
> cp /etc/rc.d/rc.local rc.local_cpufreq
> cat << EOF >> rc.local_cpufreq
> #!/bin/sh

Some things have changed with cpufreq.
- in days of old there was /etc/rc.d/*ondemand that ran 60 seconds after
         startup. This means no matter what you set for cpufreq it gets
         down graded 60 sec later. disable ondemand if your os comes with
         it.
- Now days there is kernel modules that need to be loaded and effective
         before changing cpufreq stuff, otherwise it doesn't work... and
         ondemand has been moved to systemd to ensure this. So it is best
         if your os uses systemd to move you cpufreq setting script to
         systemd to replace ondemand. BTW this ondemand also waits 60
         seconds.
- newer intel cpus have a thing called "Boost" that can change your cpus
         frequency up and down above what performance sets it to. There are
         three choices here: Turn boost off in bios. Turn it off at run
         time. Set performances minimum and max speed to compensate...
         maybe higher than performance would. (yes I have more xruns at
         low latencies with Boost on)

Setting performance is not about making sure your cpu runs as fast as
possible. It is about making sure the cpu speed does not change, It seems
at speed down changes I get xruns. However, I have set cpu governor to
USER and set it hard to 800Mhz (lowest possible) and still very good xrun
performance (like none in 8 hours running) while ondemand still gives
xruns. So choose your speed and monitor cpu temperature and run it at the
speed that gives you the highest temperature you are comfortable with.

IMO you should be monitoring temperature anyway to catch dust build up or
fan failure.

--
Len Ovens
www.ovenwerks.net

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Received on Tue Aug 28 04:15:01 2018