Performance: All Things Work Together

G1GC Performance Tuning Parameters In this post, I will list some common observations from G1GC logs, and the parameters you can try to tune the performance. To print GC logs, please refer to  my blog about how to print gc logs . Threads Related In JDK9, with -Xlog:gc*=info, or -Xlog:gc+cpu=info, you can get log entry like: [12.420s][info][gc,cpu      ] GC(0) User=0.14s Sys=0.03s Real=0.02s This can give you some indication about the cpu utilization for the GC pause. For example, this entry indicates for this gc pause, total user-cpu is 0.14s, wall time is 0.02s, and system time is 0.03s. The ratio of User/Real could be used as an estimation of number of gc threads you need. For this case, 18 gc threads should be good. If you see long termination time,  User/Real less than the gc threads, you can try to reduce the number of gc threads. Here is a list of threads related parameters: Name Pa

How to Convert JDK8 GC Log Flags to JDK9 with Unified Logging: Introduction: JDK9 introduced unified logging for all JDK9 components. It provides a way for the users to configure the content of the logs. Since all the logs follow the unified format, it would make parsing easier. Users might have some difficulty finding the right tags and levels in JDK9, especially when migrating from JDK8.  This post provides some basic back ground about unified logging in JDK9, and tags and levels in JDK9 corresponding to JDK8 flags for GC logging. JDK9 Unified Logging: With a JDK9 build, you can logging help by "java -Xlog:help". Here is the output from the command ./bin/java -Xlog:help -Xlog Usage: -Xlog[:[what][:[output][:[decorators][:output-options]]]] where 'what' is a combination of tags and levels on the form tag1[+tag2...][*][=level][,...] Unless wildcard (*) is specified, only log messages tagged with exactly the tags specified will be matc