What is G1 garbage collector tuning: -XX:G1ReservePercent?

Usage:

You can set the initial size (in bytes) of the memory allocation pool:

-XX: G1ReservePercent=percent,  where percent is desired percent of the heap from 0 to 50 that's reserved as a false ceiling.

Examples:

To set the reserved heap to 20% use:

-XX:G1ReservePercent=20

Description:

G1 (Garbage First) GC is designed for apps in multi-processor environments with large memory space (more than 4GB). It is available from the JDK7 Update 4. Unlike other collectors, the G1 collector partitions the heap into a set of equal-sized heap regions (usually 1MB to 32MB) chunks, prioritizes them, and then performs the garbage collection on those chunks based on the priority. We can tune G1 with additional options, one of them is G1ReservePercent. It sets the percentage of the heap (0 to 50) that's reserved as a false ceiling to reduce the possibility of promotion failure for the G1 collector. When you increase or decrease the percentage, ensure that you adjust the total Java heap by the same amount. By default, this option is set to 10%.

Default Value:

Default value is 10%.

Errors:

None

Arguments related:

TODO link MaxHeapSize, MinHeapFreeRatio, MaxHeapFreeRatio, Xmx, Xms, NewSize

Related Posts:

• Quick start on Java GC
• Garbage collection tuning
• Garbage collectors documentation
• Quick start on Java GC

NOTE:

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