CPU Spikes on some sessions.

[jntracks]

First the basics:
mid 2012 MacBook Pro Retina 15"
OSX 10.7.5
Pro Tools 9.0.6

I'm mixing an album, so each song is a session, they vary a bit on how many vocal tracks, guitar tracks, etc. in each song, but mostly the plugins and plugin counts are similar.

They all hover about 45% to 55% CPU RTAS (not using any elastic)

The thing is on two of these sessions I get CPU spikes that shoot up to 90 or 100 for less than a second. If I have ignore errors checked I get the garbly static kind of errors when the spikes happen, and if I don't ignore errors I get a few audible errors and the biggest spikes stop playback and throw the CPU overload error.

I'm running the playback engine at 6 cores 99%. (Out of 8 cores, since it's a Ivy Bridge Core i7 CPU)

So why does this happen on some sessions and not others when they have similar track counts and plugin loads? It makes me think there is something going on in the background of the system that's messing with me.

Is there something I can check to see if something like that could be happening?

The way I set up these sessions was to import the tracks and setup the basic effects and mix on the first song, then save a template (with no media) that I create new sessions from to import the audio files for the other songs. Then I make song specific adjustments and so on.
So that's why I say the sessions are very similar by track count and plugin load, since I'm starting from the same basic mix and going from there for each song.

So why would some of the sessions I made from this template get these CPU spikes, but some don't, and the session that I saved as the template doesn't?

Thanks!

[Chief Technician]

Originally Posted by jntracks

It makes me think there is something going on in the background of the system that's messing with me.

Is there something I can check to see if something like that could be happening?

In addition to the System Usage window in Pro Tools, launch Activity Monitor (/Applications/Utilities) and choose to show all processes and sort by descending CPU usage. If another process is causing these issues, you should see some process jump to the top of the CPU usage list at the time the CPU meter in System Usage spikes.

[jntracks]

Is there a way to show a log of the activity monitor? I can't see anything spiking, the spikes don't seem to show up in the graphical cpu usage either.

I turned the polling up and I still can't see anything happening. Even the Pro Tools process doesn't seem to be spiking.

[Chief Technician]

Originally Posted by jntracks

Is there a way to show a log of the activity monitor?

If there is, I do not know how to do it.

[jntracks]

What about running PT 9 on Mountain Lion?
I'm considering trying to update the OS, like maybe there's some strange incompatibility with my Apollo Twin, or maybe some plugin....
Anything that could be causing this weirdness.

It says that mountain lion isn't certified to be compatible with pro tools 9, but I see lots of references to people running it just fine, after an installer crash workaround.

Is this something worth trying?

I've got activity monitor open on my second screen trying watch for anything weird, and besides that it seems to be getting worse instead of better... Much of the time activity monitor actually shows a dip in CPU usage at the time of the pro tools error. Now and then I see LicenseDaemon pop up to 24% or so CPU for just an instant when it stops for 6101. What does that do? Could it have something to do with this?
I'm also convinced that it's happening more and more as I continue to work on these sessions. Like they are becoming more corrupt or something. I'm going to try saving new copies of them, maybe on different drives...

[Chief Technician]

Originally Posted by jntracks

I'm also convinced that it's happening more and more as I continue to work on these sessions. Like they are becoming more corrupt or something. I'm going to try saving new copies of them, maybe on different drives...

Does the amount of real memory in use by Pro Tools continue to go up as you work? Maybe there is a memory leak.

[jntracks]

MM, that doesn't seem to be it. Sitting still at 1.82GB

So I just noticed something strange happen: I was sitting with the session open, playback stopped, and I saw the CPU (RTAS) meter bounce up and down (from 50% to the 70's and 80's) like it does when the errors happen (or the garbles, if I have "ignore errors" ticked).

So it happens even when it's not playing or recording.

[Chief Technician]

Code execution continues even when there is no playback taking place. I know you said your sessions are similar. Is there a different plug-in for this one session compared to the others? Are there more instances of a given plug-in within this session compared to the others?

[jntracks]

Yea they are similar, but not identical, like you're saying. Different numbers of vocal tracks and guitar tracks in each song, for instance.

So it's really looking like it's a some plugin I'm using, and maybe it only acts up when there are quite a few instances of it.
These sessions do have loads of Slate VCC on nearly every track. I just thought I'd be doing fine since it's showing only 45 to 55% CPU in Pro Tools. Everything is fine until it spikes and then drops back down to normal.

When I tick "ignore errors" it pushes through them and just plays garbly error sound in the monitors during the spikes. It sometimes gets several spikes in just a few seconds. Other times playing the same section there will be no spikes at all.

I guess there doesn't seem to be anything else left to check except every plugin one by one, and check how many I'm using.

That'll have to happen when this project is done. Go messing with the system in the middle of an album mix...

[jntracks]

Just to update this: I'm starting to feel like the plugin that is spiking is Slate VCC. I've loaded up some test sessions and filled up 60 tracks with that and while it takes a lot more than just VCC on every track to get up to 50% CPU it does take longer to load up than most other plugins and the more instances I put on the more the spikes above the steady CPU seem to happen.

Maybe there's something it's doing that causes inconsistent CPU usage as many of them stack in the same session?