With the image and procedure I posted above I have reproduced this particular slowdown on a WIndows 7 x64 virtual machine with fewer virtual cores than my host system has. I was able to test with multiple configurations, with all else being equal except the virtual core count.
Photoshop CC 14.2.1 with 4 virtual cores - 25 seconds
Photoshop CC (2014) with 4 virtual cores - 226 seconds
Photoshop CC (2014) with 6 virtual cores - 242 seconds
Photoshop CC (2014) with 8 virtual cores - 200 seconds
-Noel