Heap memory tuning

Many objects with data are created and destroyed in memory while streaming. Therefore it is recommended to allocate at least 1/2 of server physical memory for Java memory heap. For example, if server RAM is 32 Gb, then it is recommended to allocate 16 Gb with the following settings in wcs-core.properties file

-Xmx16g
-Xms16g

Garbage collector tuning

Garbage collector (GC) is an important part of Java VM. When GC is running, it dramatically increases the server load and may stop another tasks execution, therefore it is recommended to minimize GC launch with the following settings in wcs-core.properties file

#Disable heuristic rules
-XX:+UseCMSInitiatingOccupancyOnly

#Reduce Old Gen threshold
-XX:CMSInitiatingOccupancyFraction=70

# Use System.gc() concurrently in CMS
-XX:+ExplicitGCInvokesConcurrent

# Disable System.gc() for RMI, for 10000 hours
-Dsun.rmi.dgc.client.gcInterval=36000000000
-Dsun.rmi.dgc.server.gcInterval=36000000000

Concurrent Mark Sweep (CMS) Garbage Collector

The Concurrent Mark Sweep (CMS) collector is designed for applications that prefer shorter garbage collection pauses and that can afford to share processor resources with the garbage collector while the application is running. This collector should be considered for any application with a low pause time requirement.

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openjdk version "12.0.2":

The Z Garbage Collector

The Z Garbage Collector (ZGC) is a scalable low latency garbage collector for Java 12. ZGC performs all expensive work concurrently, without stopping the execution of application threads for more than 10ms, which makes is suitable for applications which require low latency and/or use a very large heap. You should pay attention to ZGC requires more processor resources compared to CMS GC.

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8.  After restarting WCS, the gc-core.log log files show the periodic operation of the garbage collector. To understand the working model of Z Garbage Collector, you can read the presentation.

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