Thursday, 12 November 2015

Using -Xgc:preferredHeapBase with -Xcompressedrefs

Saw this IBM Technote via Twitter: -


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"Why does the JVM report a native out-of-memory (NOOM) when using compressed references? I am using a 64bit JVM and I clearly have plenty of memory left. How can I resolve this problem?"

The IBM JVM will automatically use compressed references when using a maximum heap size less than 25GB. This automated behavior was introduced in Java 626 SR5 and Java 7 SR4*. Compressed references (CR) decreases the size of Java objects making better use of available memory space. This better use of space results in improved JVM performance. *(Java 7 SR1 and later uses compressed references by default on z/OS)
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Worth a read

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