http://mail.openjdk.java.net/pipermail/hotspot-gc-dev/2018-November/023936.html

the sun.gc.collector.2.name label "G1 stop-the-world phases" seems to
be just wrong. Looking at
src/jdk.jcmd/share/classes/sun/tools/jstat/resources/jstat_options, the
comment for sun.gc.collector.2.* and the actual code indicates that
this should actually be called something like "G1 concurrent (stop-the-
world) phases".