LrC 12.3 High CPU Usage when merely displaying a panorama; also Expand Stack doesn't work

[Jim Garrison]

This just started happening since the upgrade to 12.3.

Windows 10 22H2 with all latest updates

CPU: i7-4790K @ 4.00 GHz (not OC), 32GB RAM, 6TB Disk

Graphics: NVIDIA GeForce GTX750 Ti with driver version 527.37 (latest available)

I merged 4 images into a panorama (image 46 below):

If I am in Develop mode and have a non-panorama image selected, LrC uses almost no CPU in the background.  On changing the selection to a different (non-pano) image, there is a CPU spike for a few seconds.  However, if I select a panorama, CPU usage in LrC jumps to 65-70% for 10-15 seconds then drops to 20% and stays there for 60-90 seconds, causing my entire system to become sluggish and jerky with significant keyboard and mouse lag.  CPU consumption remains high even with LrC minimized.

Here's a screenshot of CPU usage from Process Explorer for the LrC process:

I checked driver versions and saw I was a bit out of date, so I upgraded to the latest available version.  The problem persists and may actually be a bit worse.

Note: This does NOT happen in Libray mode.

Additional note: I had the flashing white screen issue after the update to 12.3, and had to disable the technology preview.  However, I no longer see the Preferences/Technology Preview tab.

[F. McLion]

How is the GPU support set in the preferences.

12.3 is using the GPU for everything in develop, whereas before it was used for some functions only.

The GTX750Ti is a rather old GPU. Depending on the amount of dedicated RAM it has, it just is not enough for current versions of LrC. Btw., the same applies for a 4th generation of CPU which is from around 2015.

I had a similar gear (i7-4790 and GTX1050Ti) until before just a few months, and I needed to update it to be able to really work.

[F. McLion]

Please also note: https://helpx.adobe.com/lightroom-classic/system-requirements.html

[Jim Garrison]

The Technology Preview tab seems to have disappeared in 12.3.

[F. McLion]

2GB of VRAM is the absolute minimum and performancewise your gear is too old for the latest additions in Lr.

I'm afraid you can't do anything here, except replacing your probably about 8 years old PC.

[Earth Oliver]

I'm seeing massive cpu/gpu usage (on a M1 mac) when simply viewing an image in Develop. You can let it idle for as long as you want and it just keeps grinding away doing nothing.
There are lots of complaints lately about 12.3 being slow and i believe this is why.
I think Lr QE may have dropped the ball here.