CMS MxBean reports zero memory usage.

Reproducer is attached.

java -XX:+UseConcMarkSweepGC -Xmx2g TestMxBean

Following is a sample output:

CMS Old Gen: init = 701890560(685440K) used = 661176392(645680K) committed = 1340018688(1308612K) max = 1431699456(1398144K)
CMS Old Gen: init = 701890560(685440K) used = 895563976(874574K) committed = 1431699456(1398144K) max = 1431699456(1398144K)
CMS Old Gen: init = 701890560(685440K) used = 502037128(490270K) committed = 1431699456(1398144K) max = 1431699456(1398144K)
CMS Old Gen: init = 701890560(685440K) used = 1050420368(1025801K) committed = 1431699456(1398144K) max = 1431699456(1398144K)
CMS Old Gen: init = 701890560(685440K) used = 644342320(629240K) committed = 1431699456(1398144K) max = 1431699456(1398144K)
CMS Old Gen: init = 701890560(685440K) used = 1199134216(1171029K) committed = 1431699456(1398144K) max = 1431699456(1398144K)
CMS Old Gen: init = 701890560(685440K) used = 848782216(828888K) committed = 1431699456(1398144K) max = 1431699456(1398144K)
CMS Old Gen: init = 701890560(685440K) used = 1411646600(1378561K) committed = 1431699456(1398144K) max = 1431699456(1398144K)
CMS Old Gen: init = 701890560(685440K) used = 159537792(155798K) committed = 1431699456(1398144K) max = 1431699456(1398144K)
CMS Old Gen: init = 701890560(685440K) used = 16432880(16047K) committed = 1431699456(1398144K) max = 1431699456(1398144K)
CMS Old Gen: init = 701890560(685440K) used = 711410736(694737K) committed = 1431699456(1398144K) max = 1431699456(1398144K)
CMS Old Gen: init = 701890560(685440K) used = 535694768(523139K) committed = 1431699456(1398144K) max = 1431699456(1398144K)
CMS Old Gen: init = 701890560(685440K) used = 574426000(560962K) committed = 1431699456(1398144K) max = 1431699456(1398144K)
CMS Old Gen: init = 0(0K) used = 0(0K) committed = 0(0K) max = 0(0K) << === zero usage
CMS Old Gen: init = 701890560(685440K) used = 379273104(370383K) committed = 1431699456(1398144K) max = 1431699456(1398144K)
CMS Old Gen: init = 701890560(685440K) used = 560760248(547617K) committed = 1431699456(1398144K) max = 1431699456(1398144K)
CMS Old Gen: init = 701890560(685440K) used = 741187992(723816K) committed = 1431699456(1398144K) max = 1431699456(1398144K)
CMS Old Gen: init = 701890560(685440K) used = 661176392(645680K) committed = 1340018688(1308612K) max = 1431699456(1398144K)
CMS Old Gen: init = 701890560(685440K) used = 895563976(874574K) committed = 1431699456(1398144K) max = 1431699456(1398144K)
CMS Old Gen: init = 701890560(685440K) used = 502037128(490270K) committed = 1431699456(1398144K) max = 1431699456(1398144K)
CMS Old Gen: init = 701890560(685440K) used = 1050420368(1025801K) committed = 1431699456(1398144K) max = 1431699456(1398144K)
CMS Old Gen: init = 701890560(685440K) used = 644342320(629240K) committed = 1431699456(1398144K) max = 1431699456(1398144K)
CMS Old Gen: init = 701890560(685440K) used = 1199134216(1171029K) committed = 1431699456(1398144K) max = 1431699456(1398144K)
CMS Old Gen: init = 701890560(685440K) used = 848782216(828888K) committed = 1431699456(1398144K) max = 1431699456(1398144K)
CMS Old Gen: init = 701890560(685440K) used = 1411646600(1378561K) committed = 1431699456(1398144K) max = 1431699456(1398144K)
CMS Old Gen: init = 701890560(685440K) used = 159537792(155798K) committed = 1431699456(1398144K) max = 1431699456(1398144K)
CMS Old Gen: init = 701890560(685440K) used = 16432880(16047K) committed = 1431699456(1398144K) max = 1431699456(1398144K)
CMS Old Gen: init = 701890560(685440K) used = 711410736(694737K) committed = 1431699456(1398144K) max = 1431699456(1398144K)
CMS Old Gen: init = 701890560(685440K) used = 535694768(523139K) committed = 1431699456(1398144K) max = 1431699456(1398144K)
CMS Old Gen: init = 701890560(685440K) used = 574426000(560962K) committed = 1431699456(1398144K) max = 1431699456(1398144K)
CMS Old Gen: init = 0(0K) used = 0(0K) committed = 0(0K) max = 0(0K) <<=== zero usage
CMS Old Gen: init = 701890560(685440K) used = 379273104(370383K) committed = 1431699456(1398144K) max = 1431699456(1398144K)
CMS Old Gen: init = 701890560(685440K) used = 560760248(547617K) committed = 1431699456(1398144K) max = 1431699456(1398144K)
^C^CCMS Old Gen: init = 701890560(685440K) used = 741187992(723816K) committed = 1431699456(1398144K) max = 1431699456(1398144K)