This may occur if you use the I/O Safety Buffer setting in the Audio Preferences. When this setting is enabled, MainStage adds an additional output buffer to protect against overloads due to unexpected CPU spikes. The size of that additional buffer changed in MainStage 2.2. In MainStage 2.1.x it was two times I/O Buffer Size while in MainStage 2.2 it is equal to the I/O Buffer Size setting. As a result, the CPU load is increased, but the round trip latency is less than with the same settings used previously in MainStage 2.1.x.

To set MainStage 2.2 to the same latency and CPU performance as MainStage 2.1.x:

1. Set the I/O Buffer Size to the next highest setting for example, if you were running at 128 samples, set it to 256 samples
2. Turn off I/O Safety Buffer.  

Note: You may notice that the Resulting Roundtrip Latency number shown in the Audio Preferences with I/O Safety Buffer enabled is not any different between MainStage 2.2 and earlier versions, despite a smaller I/O Safety Buffer size. This is because MainStage 2.1.x did not correctly report the roundtrip latency for the I/O Safety Buffer. The latency was higher than shown in the preferences window. MainStage 2.2 accurately shows the amount of latency.