What are the -Xms and -Xmx parameters when starting JVM?

Operational detail of -Xms and -Xmx

The role of parameters

• -Xms: Affects startup efficiency by setting initial heap size.
• -Xmx: Limits max heap size, preventing java.lang.OutOfMemoryError.

Principles for usage

• Adequate -Xms improves start-up performance and reduces unnecessary garbage collection.
• Optimal -Xmx value prevents lengthy JVM pauses for garbage collection.

//-Xms, taking baby steps to efficiency!
//-Xmx, the big brother that says, "You can't take more than this!"
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Precise allocation of memory using -Xms and -Xmx

Dimensioning memory with units

• Units k, m, g represent kilobytes, megabytes, and gigabytes respectively.
• Precise memory allocation is possible using these units with both -Xmx and -Xms.

java -Xms512m -Xmx2g -jar App.jar //Little one has room to grow!
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Beyond setting memory limits

• JVM's actual memory consumption includes more than just the heap; such as native interfaces and internals.
• Plan accordingly, as total memory footprint of JVM might exceed -Xmx.

Tweaking -Xms and -Xmx in Eclipse and other applications

Setting heap size in Eclipse

In Eclipse, -Xms and -Xmx are accessible via Run Configurations → VM arguments.

Accessing JVM options

JVM options including -Xms and -Xmx can be displayed by running java -X in the terminal.

java -X //Unveiling the power settings of JVM, handle with care!
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