Old 11-06-2019, 02:59 AM   #1
Abnaxos
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Default Reaper using only one core?

I'm semi-new to Reaper and working on a small project for exercise (basically only MIDI and software synthesizers). The project got bigger and got more tracks until, at some point, Reaper started to stutter. I didn't think much, I mean, this is bound to happen at some point – although I was a bit surprised, because my computer basically still looked close to idle, mostly twiddling its thumbs and waiting for work.

Anyway, I froze some tracks to fix the stuttering. That's when I realised: Reaper was using 12% CPU while rendering multiple independent tracks. I've got a 4 core CPU with hyperthreading (→ 8 pseudo cores), so 12% CPU usage is what you get when using one “core” 100%. When rendering 8 or more independent tracks, I'd expect 100% CPU usage (or 800% counting per core). Thinking back, I've never seen Reaper using more than 12%. I restored the frozen tracks to check – Reaper was stuttering using 12% CPU. I understand that audio is naturally a very serial thing, but there's still much room for parallelisation, at least at track level. But it sure looks like Reaper is never using more than one core.

That's not possible, is it? I just can't believe that Reaper actually isn't capable of using multiple cores. I must have missed something, it must be a configuration issue. Any ideas on that?
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Old 11-06-2019, 06:55 AM   #2
Xenakios
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Quote:
Originally Posted by Abnaxos View Post
Reaper was using 12% CPU while rendering multiple independent tracks.
Are they truly independent? Are folders, aux sends/returns etc involved? Could there be a plugin that forces the processing to be serialized? Is using multiple threads/cores enabled in the Reaper preferences in Audio->Buffering? (Reaper auto-detects the number of used threads by default, maybe that went wrong on your system.)
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Old 11-06-2019, 10:20 AM   #3
Abnaxos
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Exactly the setting under Audio → Buffering is what I was looking for. It was on auto (showing 8 in the disabled box), I tried setting it explicitly to 8, to no avail.

There are sends and folders involved, but I'd say 4 tracks are truly independent (no receives → midi → (fx) → instrument → fx → out without any sends), one of them is in a separate top-level folder.

I don't know about the plugins. There were some scripts I wrote myself that I just deleted (no need anymore), a few unsuspicious packages from ReaPack (Various_functions, LearnManager, Midi convert to CC). Then there's SWS which has no official Linux build. I removed it temporarily, same thing.

It was freezing 8 tracks at 12% CPU, that should have been doable with at least 4 threads, 2 at the very least if it sees dependencies where there are none. But it's not just about freezing. Of course, I don't constantly look at Reaper's CPU usage, but I really never saw it using more than these 12%.

Also played with the "v4.x worker thread scheduling" setting, nothing.
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Last edited by Abnaxos; 11-06-2019 at 10:35 AM.
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Old 11-06-2019, 12:50 PM   #4
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I do not know if the reading is a 'Globalized' reading (or for individual cores) I think you have to use 'SMP'Machine instead of 'UP' Machine...The mpstat command can be used both on SMP and UP machines, but in the latter, only global average activities will be printed...?

so use MPSTAT or SYSSTAT commands on a SMP computer... lil more info here https://linoxide.com/monitoring-2/10...-command-line/
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Old 11-06-2019, 08:20 PM   #5
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What specific plugins are you running and how many of each? Are any of them bridged somehow (Windows plugins running in Linux)?

Do you notice PDC for any of them? You can see this in the fx browser window (when the effect is selected) at the bottom where it says "CPU" (right beside that, it says "spls"). Also you can see in the Reaper performance meter how much PDC there is per track.
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Old 11-08-2019, 12:48 AM   #6
Abnaxos
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These are the Plugin pipelines I've currently got:
  • TyrellN6 (VSTi) (2x “pure”)
  • TyrellN6 → PingPongPan
  • ReaSamplOMatic5000 (6x on two tracks for drums, i.e. one note only), no FX for now
  • MIDI Note Filter (JS) → MIDI Router/Transpose (JS) → TyrellN6 (VSTi)
  • Pianoteq 6 STAGE (E-Piano, VSTi) → MIDI CC LFO Generator (JS) → Pitch Shifter 2 (JS), ZynDistortion (VST), ZynChorus (VST), GxWahWah (LADSPA via Carla VST)
  • SF2 via Carla VSTi → 4-Tap Phaser (JS) → ZynChorus (VST)
  • TyrellN6 (VSTi) → Ping-Pong Pan (JS)
  • TyrellN6 (VSTi) → ZynPhaser 8VST)

It seems I have a thing for TyrellN6, didn't realise that until now.

All Linux native, I don't use Wine.

About the PDCs, what exactly am I looking for? Looking at the CPU info, I didn't see anything suspicious.
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