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Usage Instructions for Azul Zing Builds of OpenJDK

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These are some recommendations and extra info related to the CRaC support in Azul Zing Builds of OpenJDK (Azul Zing).

Supported CRaC Engine

Only the Warp Engine is available in Azul Zing, check CRaC Engines for more info.

System Tuning Recommendations for CRaC

Increase the VMA limit on the host system, especially for the restore.

 
sudo sysctl vm.max_map_count=10000000

Enabling GC logging and including detailed restore tracing is recommended since it helps diagnose failures and performance issues. Add the following to the command-line during checkpoint:

 
-Xlog:gc*=info:file=<path-to-gc-log> \
-Xlog:crac=debug:crac.log

To diagnose checkpoint failures due to open files, you can also add the parameter -XX:+CRaCPrintResourcesOnCheckpoint.

Another recommendation is to turn off elastic heaps (unless it is absolutely needed) by setting Xms (InitialHeapSize) equal to Xmx (MaxHeapSize).