Dual monitor issue #106397
Operating system: macOS-13.2.1-arm64-arm-64bit 64 Bits
Graphics card: Metal API Apple M2 Pro 1.2
Broken: version: 3.5.0, branch: blender-v3.5-release, commit date: 2023-03-29 02:56, hash:
Worked: (newest version of Blender that worked as expected)
Short description of error
Using a new Mac Mini Pro with single monitor (Apple Studio Display), Blender 3.5 is very fast.
Add in a second Studio display and the interface becomes 'clunky', contextual menus take sometimes 2 or 3 seconds to appear, playback is jerky.
Tried various settings in preferences but no change. Unplugging the second monitor returns good performance...
Setting 'GPU Backend' to 'OpenGL' improves things a little...
Version 3.4.1 seems to have similar issues
I seem to have solved some of the issue..
The Apple Studio Displays have 4 input ports, one Thunderbolt port and 3 USB-C ports.
The external display was plugged into one of the USB-C ports.
Swapping input to the Thunbderbolt port seems to speed things up.
Still a lot of lag on contextual menu pop-up,and selection box drag out.
So it tried reducing the Blender window to 1/4 screen, Blender becomes smooth again.
I then methodically made it bigger and bigger until the latency suddenly reappears.
Provided I leave around 15mm of gap around the edge of the Blender window with the desktop peeking around the edge, Blender stays very smooth.
Pull it a bit further out and the latency returns.
It can’t cope with absolute full screen, knock it back 5% smaller and it’s fine.
Exact steps for others to reproduce the error
[Please describe the exact steps needed to reproduce the issue]
[Based on the default startup or an attached .blend file (as simple as possible)]
I've partially been able to confirm this (though not exactly the same setup nor a very significant drop), so will investigate the issue further. It is likely a problem with the presentation engine synchronisation which possibly changes when a second monitor is attached, causing period CPU stalls on the application side.
Will update here with more information soon.
Yes, dual Apple Studio Displays here, unplugging the second monitor solves the issue.
THanks for the update...
@Nigel-Cartwright Thanks for the information! As a quick question, if you happen to have a spare moment, would you be able to give the latest 3.6.0 daily alpha a try? https://builder.blender.org/download/daily/
There are a few synchronisation changes which alter possible stalls within the window presentation system. It wasn't directly addressing this issue, but curious if there was any improvement as a result?
Though we will still investigate this directly and feed back, all of this information is helpful!
Just tried 3.6 Alpha, I'm afraid it exhibits identical problems.
Shrinking the window stops the latency, as in 3.5...
No worries, thank you for confirming, that helps rule out some causes
Hi @Nigel-Cartwright if you happen to have a moment, capturing diagnostic traces of this issue would be greatly useful.
Could you please try opening a command prompt and running either:
sudo ktrace artrace -t 2
sudo artrace -t 2
Both while the issue is occurring with two monitors connected, and while the issue is not occurring with the single monitor. This will help us understand what specific part of your setup is causing the problem, and will give us insight into how we may be able to address it.
If you are able to as well, another trace showing while the window is shrunk down would also give us information about what changes on the system when the window size changes.
Just tried that, where does it dump the log?
It's only 2 seconds...?
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NigesMainiM2Pro:~ nige$ sudo ktrace artrace -t 2
Running for 2s, trace type (full), graphics, syscall-sampling, fault-sampling, log-content, sampling every 1.000ms to output file trace002.ktrace
Adding 9 seconds of os_log data
Checking for lost events.
File is 299.17 MB.
Recorded 4710635 events over 2.12995 seconds (2211615 events/sec)
No due date set.
No dependencies set.
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