Reading Oracle Java 8 gc logs

Question

I have enabled GC logging for one of my application. Here is a part of the log. I have searched around to learn how to read this but it appears a bit different to old articles written ofr java 7 or older. I am specifically interested in the value in marked withh **. Why the value is close but diffferent in each line GC parameters as printed in log

Java HotSpot(TM) 64-Bit Server VM (25.5-b02) for linux-amd64 JRE (1.8.0_05-b13), built on Mar 18 2014 00:29:27 by "java_re" with gcc 4.3.0 20080428 (Red Hat 4.3.0-8)
Memory: 4k page, physical 8061636k(1507688k free), swap 8355832k(5938840k free)
CommandLine flags: -XX:InitialHeapSize=268435456 -XX:+ManagementServer -XX:MaxHeapSize=268435456 -XX:+PrintGC -XX:+PrintGCDetails -XX:+PrintGCTimeStamps -XX:+UseCompressedClassPointers -XX:+UseCompressedOops -XX:+UseParallelGC



85.003: [GC (Allocation Failure) [PSYoungGen: 74018K->350K(81408K)] 236281K->162693K(**256512K**), 0.0158446 secs] [Times: user=0.03 sys=0.00, real=0.02 secs]
85.200: [GC (Allocation Failure) [PSYoungGen: 75598K->406K(80896K)] 237941K->162843K(**256000K**), 0.0177163 secs] [Times: user=0.03 sys=0.00, real=0.02 secs]
85.405: [GC (Allocation Failure) [PSYoungGen: 75654K->390K(81920K)] 238092K->162915K(**257024K**), 0.0237740 secs] [Times: user=0.04 sys=0.00, real=0.03 secs]
86.921: [GC (Allocation Failure) [PSYoungGen: 77173K->2579K(81920K)] 239698K->165199K(**257024K**), 0.0315362 secs] [Times: user=0.06 sys=0.00, real=0.03 secs]
87.225: [GC (Allocation Failure) [PSYoungGen: 79373K->512K(81920K)] 241993K->163869K(**257024K**), 0.0306456 secs] [Times: user=0.05 sys=0.01, real=0.03 secs]
87.551: [GC (Metadata GC Threshold) [PSYoungGen: 42769K->594K(81920K)] 206126K->164086K(257024K), 0.0229454 secs] [Times: user=0.04 sys=0.00, real=0.02 secs]
87.574: [Full GC (Metadata GC Threshold) [PSYoungGen: 594K->0K(81920K)] [ParOldGen: 163492K->47257K(**175104K**)] 164086K->47257K(**257024K**), [Metaspace: 53346K->53346K(1099776K)], 0.9669507 secs] [Times: user=1.77 sys=0.01, real=0.97 secs]
89.126: [GC (Allocation Failure) [PSYoungGen: 76792K->1157K(82432K)] 124050K->48423K(257536K), 0.0158828 secs] [Times: user=0.03 sys=0.00, real=0.02 secs]

Thank you for your help.

Answer 1

而不是直接查看日志文件，诸如“ 垃圾收集和内存可视化器（GCMV） ”之类的工具将绘制数据图并提供统计分析。