JVM gc 算法 about ideas

[jiacai2050]

GC verbose 日志含义

• http://karunsubramanian.com/websphere/troubleshooting-gc-step-by-step-instructions-to-analyze-verbose-gc-logs/
• https://blogs.oracle.com/poonam/understanding-cms-gc-logs

The followings are other options that can be used with -verbosegc.

-XX:+PrintGCDetails
-XX:+PrintGCTimeStamps
-XX:+PrintHeapAtGC 
-XX:+PrintGCDateStamps (from JDK 6 update 4)

Minor gc

[GC [<collector>: <starting occupancy1> -> <ending occupancy1>, <pause time1> secs] <starting occupancy3> -> <ending occupancy3>, <pause time3> secs]

Full gc

[Full GC [Tenured: 3485K->4095K(4096K), 0.1745373 secs] 61244K->7418K(63104K), [Perm : 10756K->10756K(12288K)], 0.1762129 secs] [Times: user=0.19 sys=0.00, real=0.19 secs]

[jiacai2050]

Understanding JVM Internals

• http://www.cubrid.org/blog/dev-platform/understanding-jvm-internals/

[jiacai2050]

理解 gc 过程中的暂停

• http://blog.ragozin.info/2011/06/understanding-gc-pauses-in-jvm-hotspots.html

[jiacai2050]

SurvivorRatio

The SurvivorRatio parameter controls the size of the two survivor spaces. For example, -XX:SurvivorRatio=6 sets the ratio between each survivor space and eden to be 1:6, each survivor space will be one eighth of the young generation. The default for Solaris is 32. If survivor spaces are too small, copying collection overflows directly into the old generation. If survivor spaces are too large, they will be empty. At each GC, the JVM determines the number of times an object can be copied before it is tenured, called the tenure threshold. This threshold is chosen to keep the survivor space half full.

• https://docs.oracle.com/cd/E19159-01/819-3681/abeil/index.html

[jiacai2050]

Java Platform, Standard Edition HotSpot Virtual Machine Garbage Collection Tuning Guide

• https://docs.oracle.com/javase/8/docs/technotes/guides/vm/gctuning/toc.html
• http://www.oracle.com/technetwork/java/javase/tech/index-jsp-136373.html

[jiacai2050]

JVM Memory Structure

• https://www.yourkit.com/docs/kb/sizes.jsp
• http://stackoverflow.com/questions/16697135/monitor-non-heap-memory-usage-of-a-jvm

[jiacai2050]

2018-04-10T10:50:51.667+0800: 564548.110: [GC (Allocation Failure) 2018-04-10T10:50:51.668+0800: 564548.110: [ParNew: 564792K->6394K(629120K), 0.0244341 secs] 1051623K->493813K(2027264K), 0.0251491 secs] [Times: user=0.23 sys=0.02, real=0.03 secs]

• https://greencircle.vmturbo.com/community/products/blog/2016/02/12/understanding-gc-allocation-failure-messages-in-the-logs

正常行为，Allocation Failure 是 GC 触发的原因