This is actually a couple of issue but wondering if others are experiencing it and worked through it.
I am using a Dual Xeon CPU 3.2 ghz Mac Pro, Catalog on SSD, Images files on Mirrored Pair, Dedicated GPU (max I can install in my version of Mac Pro) and hardware acceleration enabled in Lightroom.
I watched the Lightroom 6 Facial Recognition tutorial which leaves out a lot of the bulk editing and says basically let it loose on your whole catalog.. NOT recommended.
I started out with a couple small portrait galleries that identified a couple hundred total people to seed facial recognition so it didn't suggest everyone is the first person I confirmed (which it will do otherwise). I have also optimized my catalog multiple times.
I have encountered the following serious performance issues and bugs with Facial Recognition.:
- Lightroom Facial Recognition goes to a ridiculous crawl after about 2000 images to be confirmed. (i.e. 2000-2300 in a couple hours, 800-1200 in the next 12 hours)
- Lightroom becomes largely unresponsive after having a fair number of images to be confirmed, even after pausing Address and Facial Recognition. So even selecting 4 rows of images can take 5 minutes with several long pauses.
- Once I select and click confirm it takes up to 2 minutes to update the "to be confirmed" list again.
- When I click on an individual at the top of the page, pause facial recognition and address lookup it still continues to "Look for similar faces" [BUG!!!!!!!!] even though all I want to do is just confirm some individuals more quickly in bulk with the images already identified.. not continue to look for more as a work around for the painfully slow responsiveness of the module.
The odd part is that with all of the performance issues Lightroom will not use more than 20-30% of my two Xeon CPUs, barely touches my GPU (<10% CPU, 30% memory), my and no more than 35% of my memory. Computer Temps are also barely above startup temperatures and 15-25 degrees cooler than when I run other applications which will consume my entire CPU and memory if I let it. I have explored Lightroom's settings but seen nothing further I can configure to speed it all up. I have also attempted the operation on images on the SSD, my drobo (known to be slow), an independent fast disk I have, and a pair of raided disks and have the same issues.
I will also note that all of my other applications seem to continue to operate just fine.. the slowness seems to be contained to the Lightroom application itself.
Lightroom version: 6.0 
Operating system: Mac OS 10 Version: 10.10 
Application architecture: x64
Logical processor count: 8
Processor speed: 3.2 GHz
Built-in memory: 18,432.0 MB
Real memory available to Lightroom: 18,432.0 MB
Real memory used by Lightroom: 5,537.5 MB (30.0%)
Virtual memory used by Lightroom: 32,240.6 MB
Memory cache size: 4,342.0 MB
Maximum thread count used by Camera Raw: 8
Camera Raw SIMD optimization: SSE2
Displays: 1) 2048x1152
Graphics Processor Info:
NVIDIA GeForce GTX 285 OpenGL Engine
Check OpenGL support: Passed
Vendor: NVIDIA Corporation
Version: 3.3 NVIDIA-10.0.31 310.90.10.05b12
Renderer: NVIDIA GeForce GTX 285 OpenGL Engine
Application folder: /Applications/Adobe Lightroom
Library Path: /Users/DryClean/Documents/Lightroom_Catalog/MyCat_LR6.lrcat
Settings Folder: /Users/DryClean/Library/Application Support/Adobe/Lightroom
Anyone have any suggestions?