P: "Synchronize Settings" very slow, using 10% CPU

Things seem to have improved, for me.

Could you also move the photo info overlay to not be an overlay, rather, in a strip above the image that can be turned on or off -- no cycle. I want to see both views combined in a strip. (add MP next to file res). I'd buy you a flight at Schilling... .

Confirmed that it's stupid fast now. As fast as any other adjustment auto-sync. Thanks!

Just updated, I think its actually slower. 

Edit:

So the problem isnt resolved at all but I have a new one for you all, cancelled the sync (which actually prevents me from doing anything more in lightroom.. so close the software). Lightroom has been closed for 10 minutes. The sync options window pops up for me out of nowhere. Fantastic. This is no longer professional software. I'm sure its fine with the latest Macbook "Pro" at the Starbucks crowd but I'm done.

Lightroom Classic 9.0 was released earlier today and contained a fix for this issue. Please give it a try and confirm it is working for you after updating. Thanks for your patience.

Same issues for me. I just rebuilt my PC (NVMe drives, 9700k, 48gb RAM, etc.), and upgraded from LR5 (which is drastically faster with develop processes), and I'm really disappointed. Things that would take under 10 seconds in LR5 (on my 8 year old computer) take 10 times longer or more. Most of what is being mentioned here is applies to my situation as well. I really hope Adobe addresses this.

We have been able to reproduce the slowness with Auto-Sync and Lens Correction and we are actively investigating it.

But we don't have a reproducible case of slowness in Sync/Copy-Paste. It will be really helpful if someone who is facing this can elaborate on what settings are being Synced or Pasted. That will help us in diagnosing and fixing the issue.

Thanks,
Chinoy

I just re-tested the bug recipe and workaround I posted 5 months ago: 
https://feedback.photoshop.com/photoshop_family/topics/-synchronize-settings-very-slow-using-10-cpu?...

I got roughly comparable results, with Sync of Enable Lens Profile Corrections to 458 photos taking less than 2 seconds, while Auto Sync taking 35 seconds. 

Tested on LR 8.4.1 / Mac OS 10.14.6 / Macbook Pro 15" (2019)

Like you I usually used Sync or Copy/Paste. I've moved completely to capture one, previews come up instantly, exports fly out of my machine.. tired of wasting time in lightroom, the simplest of things take forever. 

Did you test this workaround? Because it doesn't work for me (and I assume many others). I've never used auto sync, I always use copy/paste dev settings and sometimes Sync. Can't believe this issue still hasn't been solved yet. I know a lot of people are looking at other software solutions because of how slow Adobe is to fix this issue. (and don't get me started on trying to import video files)