C2 CompilerThread0 如果抓到的java线程dump里占用CPU最高的线程是这个，99%可能是因为服务重启了

"C2 CompilerThread0" #5 daemon prio=9 os_prio=0 tid=0x00007f20c80b3800 nid=0x57c0 runnable [0x0000000000000000]
java.lang.Thread.State: RUNNABLE