I don't know if I'm posting this in proper forum branch, but many talks on Adobe forums didn't solve the problem.
Until I upgraded from Photoshop CC 2014 to 2015 or 2017 either on OS X or on Windows 10 Pro, everything was working flawlessly. I'm advanced PC and Mac user and am far from novice in computer hardware so capable to solve issues myself in most cases. But this one seems totally unsolvable.
I don't know if the problem is in AMD graphics drivers or not, but when Photoshop core was upgraded from Flash based to HTML+JS based in CC 2015, scrolling canvas performance is terrible: framerate very low and scrolling is painfully laggy because of that. Adobe support on it's forums advices checking graphics drivers for updates, tracking hardware compatibility issues etc. even taking into account that on same system untouched CC 2014 version works beautifully.
I revealed that when scrolling is happening and GPU acceleration in Photoshop Preferences is either on or off (relaunched app each time) - it utilizes only CPU but not GPU. So no load on GPU of Radeon 7970 is observed even when GPU acceleration setting is ticked On.
Why it's so? I use latest drivers available now. All previous drivers versions also didn't solve this issue.
Thank's in advance,