I use Light room to do most of my photo work, however once in a while I need Photoshop. I open the photos in Light Room and if more work is needed I will select "Edit In PS" from the Light Room menu. The issue is that it takes up to a full minute just to open a Canon 7DmII raw file which is very frustrating. Here is what I have done to date.
Reinstalled Windows 10pro
Reinstalled my Adobe products / Light room and Photoshop.
I'm running the following equipment.
Dell T5810 workstation Xeon E5-1630 processor running at 3.7ghz
NVidia M4000 GPU 8gb memory - latest NVidia drivers
32GB ECC DDR-2400 (1200Mhz) memory
Hard drive 1 = Samsung 840 EVO 1 TB SSD = Operating system and Adobe software
Hard drive 2 = SanDisk 1 TB SSD = Scratch disc
Hard drive 3 = Crucial 2TB SSD = where all my photos are located.
2 NEC 27" multisync PA271W monitors running at 2560 x 1440 pixels 60hz
6 months ago I did not have this issue, photos would open almost instantly! I've reallocated the entire drive 2 as a scratch disc, and allowed PS to access 24gb of ram.
Sorry that Photoshop CC is unexpectedly slower while editing in image from Lightroom.
We'd like to know which exact version of Lightroom and Photoshop are you using?
Does the issue only noticeable while working with raw files from Canon 7DmII?
Also, I'd recommend that you take a look at this documentation 'Edit In Photoshop' command missing and try out the troubleshooting steps listed.
Let us know if that helps.