jstat -gc -t [pid] 1000 监控日志... ，抽取其中关键记录不一定连续
应用启动时间 2015-06-23 10:22:27 ，换算后，第二条记录时间是2015-06-24 22:35:16 ，转换过程中有毫秒级的误差，与GC日志一致。
| Timestamp | S0C | S1C | S0U | S1U | EC | EU | OC | OU | PC | PU | YGC | YGCT | FGC | FGCT | GCT |
| 130368.2 | 209664.0 | 209664.0 | 142366.4 | 0.0 | 1677824.0 | 1677824.0 | 2097152.0 | 1043374.3 | 131072.0 | 15537.9 | 80 | 18.274 | 0 | 0.000 | 18.274 |
| 130369.2 | 209664.0 | 209664.0 | 0.0 | 137896.2 | 1677824.0 | 19949.5 | 2097152.0 | 1054947.1 | 131072.0 | 15537.9 | 81 | 18.532 | 1 | 0.039 | 18.571 |
| 130374.3 | 209664.0 | 209664.0 | 0.0 | 137896.2 | 1677824.0 | 33201.4 | 2097152.0 | 1054837.5 | 131072.0 | 15537.9 | 81 | 18.532 | 2 | 0.076 | 18.608 |
以下是开启-XX:+PrintGCDetails -XX:+PrintGCDateStamps 后的部分日志：
第一步：CMS-initial-mark
2015-06-24T22:35:17.084+0800: 130368.643: [GC [1 CMS-initial-mark: 1054947K(2097152K)] 1193557K(3984640K), 0.0386010 secs] [Times: user=0.03 sys=0.00, real=0.04 secs]
- 本例中启动参数未设置-XX:+UseCMSInitiatingOccupancyOnly ，只设置了-XX:CMSInitiatingOccupancyFraction=70 ，系统根据统计数据自行决定50%触发cms gc ，而不是在70%时候。
- 格式： PrintGCDateStamps部分 [GC [1 CMS-initial-mark: OU(OC)] SU+EU+OU(-Xmx), 耗时] []
第二步：CMS-concurrent-mark
2015-06-24T22:35:17.125+0800: 130368.684: [CMS-concurrent-mark-start]
2015-06-24T22:35:17.152+0800: 130368.711: [CMS-concurrent-mark: 0.027/0.027 secs] [Times: user=0.16 sys=0.00, real=0.03 secs]
第三步：CMS-concurrent-preclean
2015-06-24T22:35:17.153+0800: 130368.712: [CMS-concurrent-preclean-start]
2015-06-24T22:35:17.164+0800: 130368.723: [CMS-concurrent-preclean: 0.011/0.011 secs] [Times: user=0.04 sys=0.00, real=0.01 secs]
第四步：CMS-concurrent-abortable-preclean
2015-06-24T22:35:17.164+0800: 130368.723: [CMS-concurrent-abortable-preclean-start]
CMS: abort preclean due to time 2015-06-24T22:35:22.481+0800: 130374.041: [CMS-concurrent-abortable-preclean: 5.216/5.317 secs] [Times: user=6.14 sys=0.11, real=5.32 secs]
第五步：CMS-remark
2015-06-24T22:35:22.486+0800: 130374.045: [GC[YG occupancy: 171097 K (1887488 K)]2015-06-24T22:35:22.486+0800: 130374.045: [Rescan (parallel) , 0.0175320 secs]2015-06-24T22:35:22.504+0800: 130374.063: [weak refs processing, 0.0005460 secs]2015-06-24T22:35:22.505+0800: 130374.064: [class unloading, 0.0074730 secs]2015-06-24T22:35:22.512+0800: 130374.071: [scrub symbol table, 0.0054870 secs]2015-06-24T22:35:22.518+0800: 130374.077: [scrub string table, 0.0013050 secs] [1 CMS-remark: 1054947K(2097152K)] 1226044K(3984640K), 0.0372980 secs] [Times: user=0.25 sys=0.00, real=0.04 secs]
第六步：CMS-concurrent-sweep-start
2015-06-24T22:35:22.525+0800: 130374.084: [CMS-concurrent-sweep-start]
2015-06-24T22:35:22.546+0800: 130374.105: [CMS-concurrent-sweep: 0.021/0.021 secs] [Times: user=0.03 sys=0.00, real=0.02 secs]
第七步：CMS-concurrent-reset
2015-06-24T22:35:22.547+0800: 130374.106: [CMS-concurrent-reset-start]
2015-06-24T22:35:22.564+0800: 130374.123: [CMS-concurrent-reset: 0.017/0.017 secs] [Times: user=0.01 sys=0.00, real=0.02 secs]