ACR Ver 17.0 Denoise AI - Strange High CPU use after denoise is complete.

I got all the new stuff today. Photoshop 27, Bridge 16, Camera Raw 18, Lightroom 15. First test was for this spinning CPU in Camera Raw following a Denoise AI. Again and sadly, it's still there. Although it appears to spin for a little less time. 25 seconds vs. 40 seconds on my system. 

I have the exact same issue when I use Denois.  The CPU will continue at aprox 70-90 percent for many minutes.  Very frustrating.  When I uncheck the Denois box the CPU returns to normal.  It all started with the 14.2 update.

Camera Raw update today - Version 17.5.0.2318. Spinning CPU not fixed. I'm just hanging in there.

Another ACR update to Version 17.4.1.2280 today. Says it's only for new camera models, but who knows.

This time I did more thorough testing, including a couple reboots, and found no runaway CPU spinning. Torture tested by Denoising a batch of 100 raws. No gradual slow down, no spinning CPU. So, fingers crossed.

Another ACR update to Version 17.4.0.2272, this one in step with a Lightroom update that does Denoise AI without the DNG file.

Doing a Denoise in ACR now takes about the same time for me. And, it still spins the CPU up to 100% after the Denoise is complete. However, it spins the CPU for only about half the time. On my Win11 system the CPU used to spin for about 40 seconds. Now it only spins for about 20 seconds. Progress, I guess.

Also, on my system when ACR is hosted in Bridge, it used to take 30 to 40 seconds for a Denoised Raw to appear in Photoshop after hitting Open in ACR. Now it only takes 4 to 5 seconds. If ACR is hosted in Photoshop, the Open is instantaneous. That's why I've been dragging/dropping Denoised Raw files from Bridge into Photoshop instead of opening in Bridge.

Today I installed a "fresh" Windows 11 Version 23H2 on my desktop PC: 12th Gen Intel Core i7-12700KF/3.60 GHz, 64GB. So, no Windows mods/hacks/debloat, no 3rd party software. Then I installed Adobe Creative Cloud, and used it to install Photoshop (26.6.1) and Bridge (15.0.4.534) and ACR (17.3.1.2227). In other words, a system as virgin and up to date as possible.

I loaded a Canon CR3 raw file into ACR with Bridge. Launched Task Manager to monitor Bridge/ACR CPU, and ticked Denoise AI. After about 8 to 10 seconds of high GPU as the Denoise Window appeared, I still saw about 40 seconds of high CPU, rising to 95% then dropping back to less than 1%. I closed ACR, reopened with the Denoised raw, and saw the same 40 seconds of high CPU.

So, I'm confident I don't have some strange gremlin in my system that causes this ACR-CPU problem. It's got to be fully contained within Adobe.

Finally got some Adobe updates via Creative Cloud today. Now we have ACR version 17.3.0.2224.

Sadly, this new version does not fix this runaway CPU problem. On my Windows 11 desktop system at least. I'm tired of asking others to test, but confident it's still there.

Just to share the pain, I'm experiencing the same issue since ACR 17.0.

Win 10, CPU i9-12900K, GPU RTX 4070 Ti Super 16GB, RAM 64GB, always latest Nvidia driver (Studio). Tried ACR 17.0 to 17.2. Always the same (btw, Technology Preview makes no difference). From Bridge and from Photoshop.

The denoising runs quickly on the GPU (with RAW files from Sony, Nikon, and Canon). Afterwards, however, as long as the corresponding images are still in ACR, the CPU load runs up to about 90% for quite a while and the work becomes completely jerky, not only in ACR. If I deactivate denoising, it drops towards zero.

But this is the part that is most bizarre: When I left-click on the title bar (top bar) of the ACR window during the 90% CPU-load and hold down the mouse button, the CPU also immediately drops towards zero. When I release the mouse button, it goes back to 90. The same happens when I open a pop-up menu in ACR (e.g. the one for selecting the sorting of the thumbnails) and then click it away again.

In addition, the CPU-fuss starts all over again when I reload already succesfully denoised RAW images into ACR! If I reload several of such images at a time this happens for each single image as soon as I select it in ACR! This last aspect makes it particularly annoying, as sometimes you want to do some re-editing. So you can't simply avoid the problem by only denoising at the end. That only helps if you then don't touch these RAW images anymore.

All this applies to all RAW files I've denoised so far (quite a lot).
If I find a solution, I'll post it of course...

I also work with a Dell XPS 15 9510 Laptop under Win 10 with i7-11800H CPU, RTX 3050 Ti GPU, 64 GB RAM - with no issues,
and with an old Dell Optiplex 5070 MT under Win 10 with i5-something CPU, RTX 3060 Ti V2 Mini GPU, 32 GB RAM - with no issues.
I compared the settings to no avail.

We finally got an update to ACR today, version 17.2. Sadly it has no fix to the CPU mystery covered in this discussion.

I have been having the exact same problem for a while now, first on I5 13500 and now on amd 7 9700x based system, I migrated my hard drives and GPU from i5 build to AMD and at first I was blaming GPU the Intel ARC a580 which can be finicky and doesn't run ACR denoise that well (takes it 65 sec, for single z9 HE raw to finish). But because of this comment you made: ''...it seems to point to some unique Windows modification, or some 3rd party add-on. I do a lot of Windows debloating'',  now I am pretty sure that is the problem as I have also installed debloated Windows 11 on both of my systems and it must have introduced a bug somewhere.