Can someone make sense of the G1 garbage collector output?

I am running a Java program with the G1 garbage collector using the following options: -XX:-UseBiasedLocking -XX:+UnlockExperimentalVMOptions -XX:+UseG1GC -verbose:gc -XX:+PrintGCTimeStamps -XX:+PrintGCDetails -Xloggc:/var/tmp/gclog.out The output looks like this... 44900.297: [GC pause (young)44900.386 (initial-mark), 0.08894851 secs] : [GC concurrent-mark-start] [Parallel Time: 83.7 ms] [GC Work

[cco]

G1GCが吐き出すログ内容について丁寧に説明しているstackoverflowのレス。OpenJDK7のソースリストも提示されてる。