This bug was originally marked as duplicate of bug 192573, that is already resolved. This bug is still valid, so this seems to be another bug, but it might be related.
Build: NetBeans IDE 8.0 (Build 201403101706)
VM: OpenJDK 64-Bit Server VM, 24.75-b04, OpenJDK Runtime Environment, 1.7.0_75-b13
GUEST: doing nothing- -
Maximum slowness yet reported was 25393 ms, average is 25393
Created attachment 152469 [details]
The whole time is spent in sun.java2d.loops.Blit.Blit() method. Reassigning.