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Java Tuning

Default JVM Configuration

With the resources described in Server (12GB Memory, 8 Core), Java autoconfigures the following values:

  • InitialHeapSize: 197132288 (~ 197MB)

  • G1HeapRegionSize: 2097152 (~ 2MB)

  • MaxHeapSize: 3135242240 (~ 3.1GB)

  • MinHeapSize: 8388608 (~ 8MB)

  • SoftMaxHeapSize: 3135242240 (~ 3.1GB)

  • UseContainerSupport: true

  • UseG1GC: true

  • UseParallelGC: false

  • UseSerialGC: false

  • UseShenandoahGC: false

  • UseZGC: false

For microservices running in Docker containers with the specified server resources, the following JVM arguments are recommended:

-Xmx1g -Xms256m -XX:G1HeapRegionSize=8M -XX:+UseG1GC -XX:+UseContainerSupport -XX:MaxGCPauseMillis=100 -XX:+UseStringDeduplication -XX:MinHeapFreeRatio=20 -XX:MaxHeapFreeRatio=35 -XX:+ParallelRefProcEnabled -XX:+ExitOnOutOfMemoryError

Explanation of Arguments

Argument

Description

-Xmx1g

Sets the maximum heap size to 1GB. This is a conservative setting that allows multiple services to run on the same host without exhausting memory.

-Xms256m

Sets the initial heap size to 256MB. Starting with a smaller heap reduces startup time and memory usage when the service is lightly loaded.

-XX:G1HeapRegionSize=8M

Sets the G1 garbage collector region size to 8MB. Larger regions can improve performance for services with larger heaps.

-XX:+UseG1GC

Enables the G1 garbage collector, which is designed for applications with large heaps and predictable pause time requirements.

-XX:+UseContainerSupport

Enables container awareness, allowing the JVM to detect container memory limits and CPU resources.

-XX:MaxGCPauseMillis=100

Sets a target for maximum GC pause time of 100ms. This helps maintain responsiveness in microservices.

-XX:+UseStringDeduplication

Enables string deduplication, which reduces memory usage by sharing identical String objects.

-XX:MinHeapFreeRatio=20

Sets the minimum percentage of free heap space after a GC cycle.

-XX:MaxHeapFreeRatio=35

Sets the maximum percentage of free heap space after a GC cycle.

-XX:+ParallelRefProcEnabled

Enables parallel reference processing, which can reduce GC pause times.

-XX:+ExitOnOutOfMemoryError

Ensures container orchestration can properly handle OOM situations

Last modified: 18 May 2025
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