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Logic: freezing doesn't freeze! CPU save trick!

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Re: Logic: freezing doesn't freeze! CPU save trick!

Postby Dr Huge Longjohns » Wed Sep 18, 2019 10:57 am

So is this normal? Play midi track with ARC, loads of CPU hit. As you say, track active but not playing, loads of CPU. Track not active, CPU drops away. Switch track to active, no CPU until you hit play?
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Re: Logic: freezing doesn't freeze! CPU save trick!

Postby desmond » Wed Sep 18, 2019 11:12 am

Dr Huge Longjohns wrote:So is this normal? Play midi track with ARC, loads of CPU hit. As you say, track active but not playing, loads of CPU. Track not active, CPU drops away. Switch track to active, no CPU until you hit play?

Plugins on tracks in Logic only consume CPU for plugins when they are actively processing audio. This means either in playback, where there are MIDI notes or audio data on the track, and/or when the track is actively doing something (eg, a software instrument track is selected for live real time playing, or an audio channel is in input monitor mode or recording).

Auxes, outputs, input channels etc are always active and so plugins on them will always be processing and therefore consuming CPU.

Logic tries hard to optimise CPU use, to deactivate plugins where they are not required, but at the end of the day, if you are whacking on heavy CPU plugins, then when that processing is required, it's going to be a heavy CPU hit.

The biggest factor is software instruments when the track is selected, as for efficiency and latency reasons this forces all the plugins on that track, *and* other plugins in use (eg, plugins on any auxes that the software track feeds, and outputs), get forced onto the *same* CPU core. Depending on your plugins and projects, this can require more processing than a single core can provide (even though you may well have other cores completely inactive). In these cases, you can turn off plugins temporarily, and/or use Low Latency Mode.
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Re: Logic: freezing doesn't freeze! CPU save trick!

Postby Dr Huge Longjohns » Wed Sep 18, 2019 12:01 pm

this forces all the plugins on that track, *and* other plugins in use (eg, plugins on any auxes that the software track feeds, and outputs), get forced onto the *same* CPU core.

So does Unquantized's suggestion earlier in the thread move the plugin processing to two different cores? ie sending the track to a new track via its outputs?
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Re: Logic: freezing doesn't freeze! CPU save trick!

Postby desmond » Wed Sep 18, 2019 12:10 pm

Dr Huge Longjohns wrote:So does Unquantized's suggestion earlier in the thread move the plugin processing to two different cores? ie sending the track to a new track via its outputs?

As previously said, in Live mode, *all* plugins that the live track requires are moved onto one core.

If you've split your plugin processing up into three tracks and auxes to help distribute the load across cores in playback, *all* those plugins will come back onto one core in Live mode. This is why I said that it can be problematic if you have channels that require more processing than one core alone can handle, because in Live mode you'll likely CPU overload Logic which will complain.

When you deselect the track, it comes out of Live mode, and plugins on different channels are distributed among other cores as Logic decides.
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Re: Logic: freezing doesn't freeze! CPU save trick!

Postby Dr Huge Longjohns » Wed Sep 18, 2019 12:21 pm

OK, I'm with you. Thanks for all your input, very interesting thread, for me at least!
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Re: Logic: freezing doesn't freeze! CPU save trick!

Postby ManFromGlass » Wed Sep 18, 2019 12:53 pm

Interesting for me as well. I was having a similar problem with some of the patches from the Kepler instrument. It appears that my old tower with maxed out ram and 12 cores just can’t handle some of the demands of some of the new generation plugs and instruments.
The Spitfire people were very helpful in getting me sorted.
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