I'm running Jack in realtime mode as a normal user with the lowlatency+capabilities PlanetCCRMA kernel.

$ jackstart --verbose --realtime --driver alsa --device hw:0 --rate 44100 --period 128 --nperiods 2 --playback --dither shaped

I'm using CVS Pd devel with CVS IEMLIB and 0.7.6 release Gridflow.

I start Pd, and CPU usage* goes up to 45% (from 8% without Pd running, some other apps are busy). This is with no patches open and audio off.

Now the strange bit:

I turn audio on in the Pd main window, and CPU usage drops back down to 10%!

Turn audio off again, back up to 45%. Somehow having Pd audio off uses up 35% of my CPU time

What is going on here??

• CPU usage measured with the Gnome panel applet System Monitor 2.2.0.

$ cat .pdrc -verbose -jack -noadc -audiobuf 2 -blocksize 64 -sleepgrain 10 -midiindev 1 -midioutdev 1 -path /home/claude/claudiusmaximus -lib /home/claude/public/development/pure-data-devel/pd/externals/gridflow-lib/gridflow -path /home/claude/public/development/pure-data-devel/pd/externals/gridflow-abstractions -lib /home/claude/public/development/pure-data-devel/pd/externals/iem-lib/iemlib1 -lib /home/claude/public/development/pure-data-devel/pd/externals/iem-lib/iemlib2 -lib /home/claude/public/development/pure-data-devel/pd/externals/iem-lib/iem_mp3 -lib /home/claude/public/development/pure-data-devel/pd/externals/iem-lib/iem_t3_lib -path /home/claude/public/development/pure-data-devel/pd/externals/iem-abstractions

$ /home/claude/public/development/pure-data-devel/pd/bin/pd reading startup file: /home/claude/.pdrc sys_audioapi 5 Pd version 0.37.1 devel compiled 19:56:47 Jul 10 2004 port 5400 Waiting for connection request... TCL_LIBRARY="/home/claude/public/development/pure-data-devel/pd/tcl/library" TK_LIBRARY="/home/claude/public/development/pure-data-devel/pd/tk/library" "/home/claude/public/development/pure-data-devel/pd/bin/pd-gui" 5400 ... connected pd_startgui : updater thread 16386 launched global soundfiler thread launched, priority: 0 Soundfiler sleeping device 1: tried /dev/midi READ/WRITE; returned -1 device 0: tried /dev/midi00 READ/WRITE; returned 7 opened 1 MIDI input device(s) and 1 MIDI output device(s). input channels = 0, output channels = 2 tried /home/claude/public/development/pure-data-devel/pd/externals/gridflow-lib/gridflow.pd_linux and succeeded setting up Ruby-for-PureData... (done) [gf] This is GridFlow 0.7.6 within Ruby version 1.8.1 [gf] base/main.c was compiled on Jul 10 2004, 22:03:57 [gf] startup_cpu: using MMX optimisations tried /home/claude/public/development/pure-data-devel/pd/externals/iem-lib/iemlib1.pd_linux and succeeded iemlib1 (R-1.15) library loaded! tried /home/claude/public/development/pure-data-devel/pd/externals/iem-lib/iemlib2.pd_linux and succeeded iemlib2 (R-1.15) library loaded! tried /home/claude/public/development/pure-data-devel/pd/externals/iem-lib/iem_mp3.pd_linux and succeeded iem_mp3 (R-1.15) library loaded! tried /home/claude/public/development/pure-data-devel/pd/externals/iem-lib/iem_t3_lib.pd_linux and succeeded iem_t3_lib (R-1.15) library loaded!