JVM Garbage Collection logs, you do not want to ignore them! - Reversim Summit 2015
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The document discusses the intricacies of JVM garbage collection (GC) logs and their importance in performance tuning. It outlines how to log GC activities, suggesting specific command line options and explaining the process of interpreting log data. It also emphasizes the significance of managing overhead and adjusting heap size to optimize performance.
![The GC Log
2014-03-04T14:58:04.184+0000: 112134.528:
[Full GC [PSYoungGen: 1987780K-
>0K(266920448K)] [ParOldGen: 536855033K-
>340775638K(538269056K)] 538842813K-
>340775638K(805189504K) [PSPermGen: 38132K-
>38120K(67968K)], 310.6279200 secs]
[Times: user=5357.69
sys=2.73,
real=310.64 secs]](https://image.slidesharecdn.com/reversimsummit2015final-150312152653-conversion-gate01/85/JVM-Garbage-Collection-logs-you-do-not-want-to-ignore-them-Reversim-Summit-2015-14-320.jpg)
JVM Garbage Collection logs, you do not want to ignore them! - Reversim Summit 2015
- 1. Reversim Summit 2015 JVM Garbage Collection logs, you do not want to ignore them! Haim Yadid - Performize-IT
- 2. 3 2 1
- 4. About Me: Haim Yadid •22 Years of SW development experience •Performance Expert •Consulting R&D •Training http://il.linkedin.com/in/haimyadid lifey@performize-it.com www.performize-it.com blog.performize-it.com https://github.com/lifey @lifeyx
- 6. GC •You allocate • myObject = new MyClass(2015) •GC cleans •So everything is cool !
- 9. Overhead GCtime ————— Total Time
- 10. Logging GC activity Add the following to the command line -XX:+PrintGCDetails -XX:+PrintGCTimeStamps -XX:+PrintGCDateStamps -Xloggc:<logfile>
- 11. When should I use it ? Always In production ?
- 13. Log File Rotation -XX:+UseGCLogFileRotation Control log file size -XX:GCLogFileSize=1000 Number of log files -XX:NumberOfGCLogFiles=10 Starting from Java 7 Tuning Memory: Tuning GC
- 14. The GC Log 2014-03-04T14:58:04.184+0000: 112134.528: [Full GC [PSYoungGen: 1987780K- >0K(266920448K)] [ParOldGen: 536855033K- >340775638K(538269056K)] 538842813K- >340775638K(805189504K) [PSPermGen: 38132K- >38120K(67968K)], 310.6279200 secs] [Times: user=5357.69 sys=2.73, real=310.64 secs]
- 15. Whats nice about GC log They are not human readable Takes time and knowledge to understand Not machine readable Good luck writing a parser
- 16. GCViewer
- 18. What can we do about it ?
- 19. So what are we doing with it? Overhead should be less than 5% Usually high overhead is due to heap too small Make your heap larger and reduce overhead
- 20. So what are we doing with it? shenandoah reduce footprint Tune JVM