[LAU] Again: JACK using too much CPU after a while

Len Ovens len at ovenwerks.net
Thu Aug 25 00:12:38 UTC 2016

On Wed, 24 Aug 2016, Ffanci Silvain wrote:

> Hey hey everyone,
> I've looked more into this problem and found that JACK will start by using 
> between one and two percent of the CPU, but will gradually require more. 
> After a day JACK's CPU usage stands at about 65-85%.
> Usage: currently only mpv (multimedia player, completely shut down after 
> every use). No persisting audio connections, no other realtime and CPU hungry 
> applications.
$ uptime
  16:52:06 up 25 days, 19:50, 16 users,  load average: 1.39, 0.82, 0.43
DSP with Ardour running 3.6 to 3.8% (only two plugins fluidsynth and 
reasonable synth just now) 
i5 at 3.4Gh, 8Gram, FF has over 10 tabs open. Cpu on all cores less than 
10%. PCU gov perfomance... only 1 ice1712 card here. Oh you have 256, cpu 
at 256 is the same, DSP is  7.7%

> JACK Version: 0.121.3
> Kernel Version: 3.9.0-rc6 SMP PREEMPT
> CPU scheduling/scaling_governor: powersave
> CPU setting: 800MHz single-core (of a 3GHz quadcore)

While I have run at 800Mh for a long time (on a single core atom of all 
things) with no xruns, I was using the userspace cpu gov. Any speed change 
(in the down direction) gives me xruns. Of course CPU usage and DSP go up 
as CPU speed goes down. WHen jack first gets started powersave will give 
cpu close to full speed, as jack idles, cpu speed goes down and cpu used 
to keep up with jack's unchanging needs goes up.

Set Cpu to performance. Based on my CPU temperature readings, power use 
doesn't change much.

Len Ovens

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