我正在运行一个启用G1GC的java应用程序，并打印gc日志，如下所示：
[4074.182s][info][gc] GC(1017) Pause Young (Normal) (G1 Evacuation Pause) 6869M->6115M(16384M) 7430.860ms
[4082.328s][info][gc] GC(1018) Pause Young (Normal) (G1 Evacuation Pause) 6875M->6121M(16384M) 7058.485ms
[4089.592s][info][gc] GC(1019) Pause Young (Normal) (G1 Evacuation Pause) 6881M->6126M(16384M) 6172.693ms
[4105.799s][info][gc] GC(1021) Pause Young (Normal) (G1 Evacuation Pause) 6892M->6137M(16384M) 6845.922ms
[4114.418s][info][gc] GC(1022) Pause Young (Normal) (G1 Evacuation Pause) 6897M->6142M(16384M) 7563.613ms
[4122.805s][info][gc] GC(1023) Pause Young (Normal) (G1 Evacuation Pause) 6902M->6148M(16384M) 7326.923ms
[4131.270s][info][gc] GC(1024) Pause Young (Normal) (G1 Evacuation Pause) 6908M->6155M(16384M) 7402.222ms
[4140.574s][info][gc] GC(1025) Pause Young (Normal) (G1 Evacuation Pause) 6915M->6161M(16384M) 8226.283ms
[4149.429s][info][gc] GC(1026) Pause Young (Normal) (G1 Evacuation Pause) 6921M->6167M(16384M) 7779.282ms
[4157.078s][info][gc] GC(1027) Pause Young (Normal) (G1 Evacuation Pause) 6927M->6172M(16384M) 6559.166ms
我对这个日志的理解是：
[4074.182s][info][gc] GC(1017) Pause Young (Normal) (G1 Evacuation Pause) 6869M->6115M(16384M) 7430.860ms
As per my understanding this shows that 4074.182 seconds after application started, a young generation
Stop the world gc was kicked in, and heap size before gc heap size was 6869M
and after gc it reduced to 6115M and it took 7430.860ms (more than 7 seconds).
我的问题：
1. Is this young gc stopping all the application threads ?
2. If it is stopping all the application threads then looks like application is not
running at all during all these gc logs were printed because:
after [4074.182s] young gc kicked in and it took aroung 7.5 seconds (7430.860ms)
after ~8 seconds, [4082.328s] yound gc kicked in again and took around 7 seonds and so on.
So it looks like application is not getting any free slot here to run ?
是的，您的应用程序已停止，在此期间所有线程都将暂停。有趣的是，GC只能在6-7秒内回收700MB左右，这绝对是可怕的。如果没有调试消息，就不可能说出为什么会发生这种情况，可能是机器上启动了线程，可能是区域之间的连接太多，因此扫描记住的集合花费了大量时间，或者任何其他原因。
但最重要的是，在这些周期中，应用程序的性能非常糟糕；你说得对。