A recent GC log indicated a much larger than expected maximum time attributed to "swap remembered set" which is part of initial mark.

From @kemperw:

                              Category | Count | Total | GeoMean | Average | Minimum | Maximum
              Pause Init Mark (N) | 20508 | 66382.840 | 3.206 | 3.237 | 2.330 | 43.880
       Swap Remembered Set | 20508 | 40302.510 | 1.943 | 1.965 | 1.510 | 42.790
    Prepare Regions for Mark | 20508 | 12876.900 | 0.594 | 0.628 | 0.440 | 2.900

Examination of the code indicated that we might do a bit of refactoring which may or may not affect the variability here, but which may be of independent value.

The variation in times will be measured and characterized as well to determine the cause of the long time.