java GC日志该怎么看？

Question

{Heap before GC invocations=70426 (full 39): par new generation total 917504K, used 849770K [0x0000000730000000, 0x0000000770000000, 0x0000000770000000) eden space 786432K, 100% used [0x0000000730000000, 0x0000000760000000, 0x0000000760000000) from space 131072K, 48% used [0x0000000760000000, 0x0000000763dda9d8, 0x0000000768000000) to space 131072K, 0% used [0x0000000768000000, 0x0000000768000000, 0x0000000770000000) concurrent mark-sweep generation total 1050496K, used 735717K [0x0000000770000000, 0x00000007b01e0000, 0x00000007f0000000) concurrent-mark-sweep perm gen total 262144K, used 44072K [0x00000007f0000000, 0x0000000800000000, 0x0000000800000000) 2017-03-11T17:52:34.524+0800: 86930.373: [GC2017-03-11T17:52:34.524+0800: 86930.373: [ParNew Desired survivor size 67108864 bytes, new threshold 15 (max 15) - age 1: 7498968 bytes, 7498968 total - age 2: 10419016 bytes, 17917984 total - age 3: 9045656 bytes, 26963640 total - age 4: 3149912 bytes, 30113552 total - age 5: 1557968 bytes, 31671520 total - age 6: 1181200 bytes, 32852720 total - age 7: 900696 bytes, 33753416 total - age 8: 1135200 bytes, 34888616 total - age 9: 1545448 bytes, 36434064 total - age 10: 1038000 bytes, 37472064 total - age 11: 1199288 bytes, 38671352 total - age 12: 840296 bytes, 39511648 total - age 13: 1264520 bytes, 40776168 total - age 14: 1005752 bytes, 41781920 total - age 15: 1008152 bytes, 42790072 total : 849770K->62511K(917504K), 0.0296150 secs] 1585488K->798923K(1968000K), 0.0299000 secs] [Times: user=0.11 sys=0.00, real=0.03 secs] Heap after GC invocations=70427 (full 39): par new generation total 917504K, used 62511K [0x0000000730000000, 0x0000000770000000, 0x0000000770000000) eden space 786432K, 0% used [0x0000000730000000, 0x0000000730000000, 0x0000000760000000) from space 131072K, 47% used [0x0000000768000000, 0x000000076bd0bf30, 0x0000000770000000) to space 131072K, 0% used [0x0000000760000000, 0x0000000760000000, 0x0000000768000000) concurrent mark-sweep generation total 1050496K, used 736411K [0x0000000770000000, 0x00000007b01e0000, 0x00000007f0000000) concurrent-mark-sweep perm gen total 262144K, used 44072K [0x00000007f0000000, 0x0000000800000000, 0x0000000800000000) } 上面是我的一个GC日志，我想问这种日志该怎么看呢？之前只是学过一些理论的东西，头一次接触真正的GC日志

Answer 1

可以看看深入理解java虚拟机... 里面有讲解..

Answer 2

1、数字“11.569：”代表了GC发生的时间，这个数字的含义是从Java虚拟机启动以来经过的秒数。
2、[ParNew表示GC发生的区域，这里的显示跟GC收集器类型有关，这里表示用ParNew收集器
3、859714K->96106K(917504K), 0.0484250 secs，表示GC前该内存区域已经使用的容量-->GC后该内存区域使用容量(该内存区域总容量)
4、859714K->96106K(1966080K), 0.0486090 secs，表示GC前java堆已使用容量-->GC后java堆已使用容量(Java堆总容量)，该内存区域GC所占用的时间。
5、[Times: user=0.19 sys=0.00, real=0.05 secs]表示程序耗时、系统耗时、实际耗时。这里user的时间超过real的时间，这是正常的，表示是多线程进行CPU切换，叠加了多线程的时间。