ardour/plugins using excessive cpu

I’m having a bit of a problem and I’m hoping one of you guys have an idea.

My machine is a P4 3.4GHz with 1GB of RAM.
My drive subsystem is an Ultra160 SCSI hardware RAID-5 system with 4, 18GB 10k drives.

I’m running Ardour on Kubuntu 7.10 (8.04 is downloading right now) which has ardour 2.0.5 on it and I’ve been having some serious problems when working on even smallish projects.

An example is I have a song we’re mixing. It has maybe 15-20 tracks, and when ardour is started up with that session, it will stand idle at 10% cpu usage if all the plugins are bypassed. If I activate the plugins, usage will go up to about 30% idle and range up to about 40-50% when playing. I’m using maybe 10 plugins total of various types on several tracks and busses. If I bypass and activate those plugins a few times the machine will go up to 100% cpu usage and issue constant xruns and either pop the speakers, or issue no audio at all.

If I have a working session, and close ardour and reopen it. All the plugins will become tainted in some way so that even just opening ardour causes 100% usage and constant xruns until I disable all the plugins. If I reenable them it will go right back to 100%. If I delete the plugins and add the exact same ones back again, it will play with the normal 40-50% usage again until I further work on them…

This happens with all plugins, I’ve used the steve harris plugins, CAPS, and TAP… All of them exhibit this behavior.

Any ideas?

My system is far inferior to yours, but I had significantly positive results in terms of CPU usage by dedicating a single drive/partition on a dedicated drive to all ardour audio files.

If you have a multicore processor, you might be able to map one processor for basic recording processes and have the other thread handle plugin processing, if you use a lot of plugins. I’m not sure how to do this, though…just going off what I’ve read somewhere.

You might need to check the priorities assigned to relevant processes. There is some good information related to this if you search for ‘configure jack realtime’…

Also, I’m not sure, but I think running a RAID isn’t always ideal for audio applications. I used to run a RAID 0, but dropped it for a straight hard disk configuration, and it works very well. My drives are fast (SATA 3.0, 16 Mb cache), though.

Upgrade to a newer version of Ardour, and try using Denormal protection from the Options menu. To understand more about denormals, see

I got the upgrade to kubuntu 8.04 done today and the issue seems to have cleared with ardour 2.3, at least so far.

I still get up to about 30% usage when playing and about 5-10% idle, but that’s livable. My only issue now is the new rt kernel included with 8.04 seems to be drastically broken, so I have to run with the generic kernel and that causes xruns anytime something in the background kicks in.

Thanks for the ideas!

Well, the constant 100% usage issue appears resolved, but the cpu usage is still quite excessive. While playing it is averaging about 30-50% and spiking to 100% which generates an xrun. I don’t attribute this to other processes in the background at this point as I’ve reniced both ardour and jackd to -19 and the xruns continue. top shows ardour being the prime consumer of cpu cycles.

I’m going to move the file to another drive and see if that helps… i have more investigation to do. I’m going to look into denormals and I’ll let you know what I find.