Hello,
I use photoshop cc 2017 and currently I use it too much lately and I had insufficient ram memory problems and when starting it took too long. I wanted to put the solution that I carry out and if you have happened and how you have solved it, if you have done this same as me. To begin with, I have 12 GB of RAM and Photoshop only recognized 6 GB and in the ideal range I had it at 60 or 70 in preferences / performance. My laptop is an i5 6300 hq, gtx 960m, windows 10 pro and 12gb of ram. I did this from the video that I leave you below and it worked for me, now it is flying. I don't know if you have done it too and if it happened to you. I leave the video here. For those who happen to them, they already have a solution.
https://www.youtube.com/watch?v=3MP3NKqezucThe variation is that in the registry you get something different than 120, such as 110 or 130, it is the same you have to enter ai. Then after going to performance in photoshop and preferences and set the ideal range to the maximum, that is, 100%. This is how my problems were solved.