Huge peaks when Send(s) ON?

[Danny Wyatt]

I've been experiencing some peaks on my CPU and decided to start experimenting.

I thought it could be some plugin, maybe the Sampler had too many voices, maybe it was because I was using too many Space Designer instances, etc. Sure, all these things together affect the CPU, but having sudden peaks doesn't seemed very normal. It would went from 10% to 75% or even 100%. So now I only have 1 Instrument with a Sampler and a few other stock plugins. I'm sending it to 4 sends. I have 5 Auxs all of them with either 1 or 2 Space Designer instances, Chromaverb, PlatinumVerb, Valhalla. This is on purpose. I wanted to see if these just being turned ON would affect the CPU, and no.

If the song is stopped and the sends are all turned OFF, the Performance Meter hits probably 7% to 10% on average.
When I turn the first Send ON, it hits around 20% on average, going to maybe 25% here and there.
As soon as I turn the 2nd send ON, that's when things go crazy! It peaks at 50% on average, going up to 75% or even 100% sometimes.
And remember, the song is not playing at all.

The instrument's track is not armed. I even tried creating an audio track and select it, just in case, but no difference.

Is there a reason why having the Sends turned ON creates such peaks?

Things I'm noticing:
When I disable the Chromaverb instances (I have 4 total, 1 per aux), it goes down significantly!
One of the auxs with 2 Space Designer instances, when I turn those 2 SP off, it goes down to 25% on average (with all ChromaVerb turned off as well).

So it seems that there's a combination of things here, but what's confusing is that if all plugins are ON, but the sends are OFF, the average is 7% to 10%. I don't even see any crazy peaks ever. Pretty constant.

 

Any tips? Any explanation?

[Atlas007]

That's an interesting question, but I think only coding staff could reveal the ins and outs of that matter. Otherwise I have the feeling the rest would only be speculative assumption, although possibly nearing the truth...

[des99]

Some general notes on this (these things are often complex and very project/plugin dependent to comment specifically):

Plugins on aux channels are generally processing all the time once activated (even when Logic is stopped) unless there is nothing to process. So if you put a bunch of reverbs on auxes (Chromaverbs are quite CPU heavy I think), but no audio has passed yet, there probably won't be much CPU load as the plugins have nothing to do yet.

When you turn a send on, there is now an audio path to the plugins on that aux channel you're sending to, so the CPU is engaged and the plugin starts working. The more sends you turn on, the more plugins on those aux channel you sending to are processing.

Is it just peaking initially when you turn on a send, and then it settles down to a reasonable CPU level? Or is it jumping up far higher than you'd expect and staying there? In other words, if you use two Chromaverbs and normally the CPU hit for them is 20%, but you perform the procedure as outlined, the CPU jumps up to 100% and stays there?

Also, remember that the core assignment is dependent on whether Live mode is in use, so make sure nothing into the signal path is in live mode, otherwise everything in that signal path will be forced onto one core as we well know - if so, so try re-running your test making sure nothing in that signal path is in Live mode, and see whether the behaviour remains the same or changes.

[Danny Wyatt]

On 6/14/2022 at 5:50 PM, des99 said:

Chromaverbs are quite CPU heavy I think

Yes, when the Chromaverb instances are enabled, that's when I get the highest peaks

 

On 6/14/2022 at 5:50 PM, des99 said:

When you turn a send on, there is now an audio path to the plugins on that aux channel you're sending to, so the CPU is engaged and the plugin starts working

What I find it weird is that if Logic is stopped, the plugins are not doing any work yet, even if the Sends are not, you know? Sure, there's a new audio path, but there's no activity affecting the plugins yet so they are not working. I would understand that it could create the CPU to be a little higher, like 5%, but not going from 5% to 75%, for example.

 

On 6/14/2022 at 5:50 PM, des99 said:

Is it just peaking initially when you turn on a send, and then it settles down to a reasonable CPU level?

It has a super high peak initially (like 100%) then goes to 50% or 75%.

 

On 6/14/2022 at 5:50 PM, des99 said:

remember that the core assignment is dependent on whether Live mode is in use, so make sure nothing into the signal path is in live mode

Yes, on my tests I even created an audio file and selected it to avoid this.

[des99]

6 hours ago, Danny Wyatt said:

What I find it weird is that if Logic is stopped, the plugins are not doing any work yet, even if the Sends are not, you know? Sure, there's a new audio path, but there's no activity affecting the plugins yet so they are not working. I would understand that it could create the CPU to be a little higher, like 5%, but not going from 5% to 75%, for example.

Once they have been activated, bus plugins continue to process audio even if Logic is stopped (presumably to be able to respond to live incoming audio, playing software instruments etc). So you can have a bunch of (say) reverbs on busses, and have Logic not playing, but all those plugins are active.

To demonstrate this, here's a video of what happens on my system (M1 Pro):-

- I stick four Chromaverbs on an aux track. CPU performance is low, as no audio has been sent through the system and the plugins haven't yet become active

- I add an instrument plugin, and you'll see the CPU jump up significantly as all the reverbs have been turned on and are now processing. If I then do nothing, turn the instrument off, select other tracks etc, you can see the CPU power continues to be used for those reverbs. If I turn off the reverbs, the CPU goes away, if I turn them back on, they start processing again.

Logic is not playing back anything, it's been stopped the whole time.

So, processing will jump up if you have active reverbs/FX on busses, if you're suddenly going from no reverbs, to 4 Chromaverbs or something, regardless of whether Logic is in playback or not.

In this case I didn't check the behaviour turning the sends on as per your original query, I'm just showing you that contrary to what you state above regarding Logic not processing plugins when stopped, bus plugins do in fact use CPU when Logic is stopped, and this may likely explain the behaviour you see.

Edit: Ok, here's an example of the reverbs being turned on when you turn on the send and activate those plugins that way - you can see the same effect:-

(Note, the CPU peak I show when enabling the plugins is normal, it's just Logic turning the plugins on and doing the work necessary to do this as fast as possible.)

The thing to check is whether the CPU load seems wrong - ie, if four Chromaverbs on your system normally make your CPU go up 20% of a core, but in this project, you enable them, it really is only the extra four Chromaverbs you're monitoring the CPU for (ie there's no extra other plugins been added in in this test to make it a fair comparison), but the CPU% goes up 75%, then that to me would more likely indicate some kind of problem. But I suspect the behaviour you're seeing is entirely normal...

 

 

Edited June 16, 2022 by des99

[Danny Wyatt]

1 hour ago, des99 said:

presumably to be able to respond to live incoming audio, playing software instruments etc

Sure, I understand that they are active, but they are behaving as if there's audio going through them (even if this is normal behavior, it's weird to me). It's almost like having a car. Sure, if it's running (but stopped), there's gas being used. Makes sense. Once it starts moving, there's more gas being used. I thought this would be the same. I could eventually see an increase (like 10% or something like that), but not as if they are working at 100% capacity, if that makes sense. I don't have a super computer, I know, but still... That Chromaverb bastard...!

 

2 hours ago, des99 said:

The thing to check is whether the CPU load seems wrong - ie, if four Chromaverbs on your system normally make your CPU go up 20% of a core, but in this project, you enable them, it really is only the extra four Chromaverbs you're monitoring the CPU for (ie there's no extra other plugins been added in in this test to make it a fair comparison), but the CPU% goes up 75%, then that to me would more likely indicate some kind of problem. But I suspect the behaviour you're seeing is entirely normal...

I will keep testing in other projects and all that.

Thank you for clarifying things up for me!

[des99]

No problem. I agree the aux processing behaviour seems weird - it wasn't always like this, probably back in LP7 iirc bus processing wasn't active in this way, but this was I think an intentional change at some point.

I would have thought that, if Logic was stopped, no audio tracks were rec. enabled or in input monitoring, no input objects in use, and no instrument tracks selected in live mode, Logic could be reasonably confident that no audio processing was required and shut down those aux track plugins from processing... but it doesn't seem to work like that at this time...

Edited June 16, 2022 by des99

[Danny Wyatt]

33 minutes ago, des99 said:

no audio processing was required and shut down those aux track plugins from processing

Exactly... it's really weird. Oh well...