I just tried it and it indeed solves the performance issues:
Old version 1:3.18.3-1ubuntu3: $ vblank_mode=0 glxgears 27418 frames in 5.0 seconds = 5483.539 FPS
New version 1:3.18.4-0ubuntu0.1: $ vblank_mode=0 glxgears 39851 frames in 5.0 seconds = 7970.179 FPS
I just tried it and it indeed solves the performance issues:
Old version 1:3.18.3-1ubuntu3:
$ vblank_mode=0 glxgears
27418 frames in 5.0 seconds = 5483.539 FPS
New version 1:3.18. 4-0ubuntu0. 1:
$ vblank_mode=0 glxgears
39851 frames in 5.0 seconds = 7970.179 FPS