...
Total time increase for this test, which is 6 timesteps in the low-resolution nightly regression suite, is 0.0044/1.868 = 0.0023, or 2.3% of the model integration time for the ocean.
The default performance of GM on compy is here
"o_i:gm bolus velocity" - 320 320 3.200000e+02 5.133580e+00 0.019 ( 1452 0) 0.009 ( 1579 0)
Wallclock total is 5.13358
With the new GM changes
"o_i:gm bolus velocity" - 320 320 3.200000e+02 5.611241e+00 0.025 ( 1486 0) 0.010 ( 1600 0)
Wallclock total is 5.611241
This is a 8.5% increase in the GM timer. However the ocean timestep timer is about 1e7, suggesting these changes will have negligible performance impact.