P: Slow performance on Xeon CPUs

My own computer (home built) is a 6/12 core win10 machine with a Quadro gpu card, but only a 2760x1440 eizo monitor. It works fine with all 6/12 cores and with it restricted to 4/8 cores. It's a i7 5930K Haswell-E cpu, not a Zeon which is where this all started I think.

Bob Frost

I could not have written this better ! 

GPU usage isn't the problem with us high core count CPU users. We're talking about a problem that makes LR literally unusable for power users. This isn't a hobby for me, it's my job and I need this software to do what I pay for it to do. As a business owner I want them to properly address the issue at hand, and for me and many others I assume, that would mean Adobe making a public statement. Hearing tech support quietly say they are aware of the issue doesn't inspire confidence that it's being addressed as it should be. I want to see something in writing that states Adobe is working on a solution so we don't have to start migrating to another platform.

Welcome to the club! My advice is to write to Fstoppers.com and hopefully they'll pick up the story. Write them a quick message summarizing the problem and how Adobe is not addressing it. https://fstoppers.com/contact

I haven't. I just put together an AMD 1700x system, fresh install of Windows 10, running Lightroom at 4k and it's absolutely horrendous. It brought me here to read and I'm just blown away. I have used LR on my MacBook Air and MacBook Pro for over 4 years, zero issues. I put together this new machine to get faster exporting/processing of photos, and I end up being so insanely frustrated that I can't edit! It's unreal.

Has anyone had any performance improvement with the new version that came out yesterday? Lightroom CC 2015.9 ?

Message send to Fstoppers.

What value did you use for the affinity mask?

Limiting the number of processors is an old debugging trick to help identify race conditions in multi-threaded programs. There's pretty clearly some problem with how LR uses multiple processors on some CPUs.

Thank you John R. Ellis!  Did try the John R. Ellis solution, and so far LR CC runs smoothly for the first time in ages. If only I had known 3 years ago. I have had the lagging/sluggish issue for years, with different versions of LR (both CC and standalones), and always suggested memory leak as the culprit.  For now, I made a .bat-file with John's line, and will test it thoroughly. So far Adobe have only suggested various work-arounds (smaller catalogs, no batch editing etc.), but reducing the core affiliation actually taste like a real solution (and pin-pointing a serious software issue)

w10x64 w/i7 3770K cpu @3.5ghz. OS, storage and scratch disks are on 3 separate 0-raided ssd's. The gpu is an amd r9 380. Asus Maximus V mobo