By default, this option is enabled, and compressed pointers are used when Java heap sizes are less than 32 GB. To disable the perfdata feature, specify -XX:-UsePerfData.ĭisables the use of compressed pointers.
Disabling it suppresses the creation of the hsperfdata_userid directories. This option is enabled by default to allow JVM monitoring and performance testing. I didn't find an official doc, but it seems that this prevent GC from writing in the file system.Įnables the perfdata feature. The performance effect of explicit garbage collections can be measured by disabling them using the flag -XX:+DisableExplicitGC, which causes the VM to ignore calls to System.gc().Įnables parallel reference processing. This can force a major collection to be done when it may not be necessary (for example, when a minor collection would suffice), and so in general should be avoided. By default, this option is disabled and all pages are committed as JVM heap space fills.Īnother way that applications can interact with garbage collection is by invoking full garbage collections explicitly by calling System.gc().
The option can be used in testing to simulate a long-running system with all virtual memory mapped to physical memory. This gets all pages into the memory before entering the main() method. By default, this option is disabled and experimental performance features are not used.Įnables touching of every page on the Java heap during JVM initialization. By default, the option is disabled and the heap is not optimized.Įnables the use of aggressive performance optimization features, which are expected to become default in upcoming releases. This sets various parameters to be optimal for long-running jobs with intensive memory allocation, based on the configuration of the computer (RAM and CPU). XX:+AggressiveOpts -XX:+AlwaysPreTouch -XX:+DisableExplicitGC -XX:+ParallelRefProcEnabled -XX:+PerfDisableSharedMem -XX:+UseCompressedOops -XX:-UsePerfData AggressiveHeapĮnables Java heap optimization.
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