Mysterious Cpu Spike


I’m currently working on a song with 6 instances of Sylenth1, 2x Gladiator and 1 Helix. There are 12 tracks, 3 sends and a number of drum samples/loops. The thing is that always in the same pattern, no 17 out of 20 patterns at 128 lines, the CPU spikes to 100% and Renoise kills the song. Now i’ve experienced some bugginess with Sylenth1 which i attributed to the SE GUI, but i’ve had other songs with as many instances of S1 without any problems, and this song is the first that behaves like this. It’s not much to go on, but i like where this track is going and i really want to hear where it ends. My gear is listed below and latency is at 480 samples, and increasing latency doesn’t seem to help. Any suggestion?

The first question is:Does it spike if you skip to position 17 in the arranger and play the specific pattern? If so this makes it quicker to find the faulty area, if not, then this will take a little longer.

If sylenth1 does not cause this (alone) you can do the following to exclude things:
Go to the preferences and go to the MISC/VST tab. Make sure the option “Default mute mode” is set to “Off” so that you can let Renoise completely ignore tracks. By default this is set to “Mute” but when you would mute tracks, the effect and instrument plugins are still triggered which makes isolating the problem a lot harder.

If you have secured yourself with this option, you can now figure out which track causes this and then test if the isolated track causes the same problem or only if a combination of tracks cause the problem.
Then start to exclude effects and see if this is a VSTI thing, if not, add a sample-only instrument and swap the instrument numbers in the affected tracks with the sample-only instrument to see if it might be a VST effect plugin.

Trial and error until you have isolated as close to the source as possible.
It makes it also for us a lot easier to help you out.

do you have any tempo changes in your song ?..I recently posted a topic about cpu load ( doubling ) by just changin the bpm with a small value

…thanks for your help at this late hour. I’m done for the night, but will continue tomorrow searching for culprit. At least now i’ve got a starting point! I’ll keep you posted :)

…no, not at all. Tempo changes within the song is something still on the ‘to learn’ list :D

May I hijack this thread and remind you to send us the song to solve this problem (if you want that problem to be solved)?
Might be a bug in a VST which causes a high CPU usage on a special BPM, but that should not happen everytime with many VSTs then…

…the problem is solved and, as always, concerned a tiny little something you’d not expect :D

  1. Loading the song for the first time - poof, Renoise crashes
  2. Start again, made sure mute mode is set to off - which is was already
  3. Playing pattern 17 did not do anything, but when i played from pattern 12 the problem emerged in pattern 17 again.
  4. Now i notice a Sylenth1 sound isn’t working. Fixed that, but still the problem persists.
  5. While playing the song muting tracks my eye caught something. On the FX column a Gladiator woosh sound is triggered [in pattern 12!] and i didn’t see a note-off in the following pattern. Could that be it?

…that was it. The fact that Gladiator never got a note-off command resulted in a CPU spike 5 patterns later. Everything is running smoothly as always…


How often does this happen? What does the Log.txt say about this?

My guess is that some VST crashes Renoise randomly at this point, but to be sure, could you please send me your log.txt (taktik@renoise…).

Have i already mentioned that I hate VSTs?

…it happens occasionally, but since i started using KillTask Renoise is cleared from RAM and restart is effortless. Mail is sent, and i love vst’s ;)

Thanks. You got no “clean” Renoise crash, Renoise just disappears, right? The Gladiator VST seems to cause this. Its shutting down the host after an internal error, so unfortunately there is nothing we can do as this is a problem in the VST itself…

…yes, Renoise disappears without notification. Thank you for the help Taktik, luckily the Gladiator issue is just minor, keeps things interesting :D