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IBM J9 VM 8
This page describes the Optimization Pack for Eclipse OpenJ9 (formerly known as IBM J9) Virtual Machine version 8.
The following parameters require their ranges or default values to be updated according to the described rules:
Notice that the value
j9vm_compressedReferencescan only be specified for JVMs compiled with the proper
--with-noncompressedrefsflag. If this is not the case you cannot actively disable compressed references, meaning:
- for Xmx <= 57GB is useless to tune this parameter since compressed references are active by default and it is not possible to explicitly disable it
- for Xmx > 57GB, since the by default (blank value) compressed references are disabled, Akamas can try to enable it. This requires removing the
nocompressedreferencesfrom the domain
The following tables show a list of constraints that may be required in the definition of the study, depending on the tuned parameters:
j9vm_newSpaceFixedis mutually exclusive with
j9vm_oldSpaceFixedis mutually exclusive with
- the sum of
j9vm_minOldSpacemust be equal to
j9vm_minHeapSize, so it's useless to tune all of them together. Max values seem to be more complex.