7.6.9 -XX:[+|-]HitachiVerboseGCPrintTenuringDistribution

-XX:[+|-]HitachiVerboseGCPrintTenuringDistribution outputs the age distribution for the Survivor area to the Java VM log file.

Description

-XX:[+|-]HitachiVerboseGCPrintTenuringDistribution specifies whether the Survivor area age distribution that is output when -XX:+PrintTenuringDistribution is specified, is to be output to the Java VM log file.

Prerequisite option

-XX:+HitachiVerboseGC

Related options

-XX:+PrintTenuringDistribution
-XX:+HitachiVerboseGCPrintDate
-XX:+HitachiCommaVerboseGC

Format of output

[id]<date>[Desired survivor:size bytes][New threshold:value]
[MaxTenuringThreshold:  max_value][age1:total_age1][age2:total_age2]...
[agen:total_agen]

The following provides details about the output.

Output item	Output content
`id`	`PTD` (Java VM log file identifier)
`date`	Start date and time of GC
`size`	Target size of the objects in the Survivor area after GC
`value`	Age threshold for Java objects that are to be promoted to the Tenured area in the next CopyGC. This value is dynamically set for each CopyGC, based on the values set for the `-XX:MaxTenuringThreshold=value` option, the memory size of the Survivor area, and the `-XX:TargetSurvivorRatio=value` option. The Java objects whose age is equal to or greater than `value` will be promoted to the Tenured area in the next CopyGC.
`max_value`	Maximum value (value specified for the `MaxTenuringThreshold` option) of the age threshold (`value`) for the Java objects that are to be promoted to the Tenured area in the CopyGC. `value` is dynamically set for each CopyGC but cannot exceed `max_value`. The Java objects whose age is equal to or greater than `max_value` will always be promoted to the Tenured area in the next CopyGC.
`total_age1`	Total size (in bytes) of 1-year-old objects.
`total_age2`	Total size (in bytes) of 1-to 2-year-old objects.
`total_agen`	Total size (in bytes) of 1-to n-year-old objects. If n is close to `max_value`, it means that an object with a long life exists.

Syntax

-XX:[+|-]HitachiVerboseGCPrintTenuringDistribution

Specifiable values

Type: String

-XX:+HitachiVerboseGCPrintTenuringDistribution: Outputs the Survivor area age distribution that is output when -XX:+PrintTenuringDistribution is specified, to the Java VM log file.
-XX:-HitachiVerboseGCPrintTenuringDistribution: Does not output the Survivor area age distribution that is output when -XX:+PrintTenuringDistribution is specified, to the Java VM log file.

Default value

If the definition item is omitted:: -XX:-HitachiVerboseGCPrintTenuringDistribution

Example

[PTD]<Wed Jan 28 17:47:10 2009>[Desired survivor:32768 bytes][New threshold:30]
[MaxTenuringThreshold:30][age1:6872][age2:9632][age3:25632]

Notes

The amount of log data that is output during CopyGC when this option is specified is two or more times the amount of data that is output when this option is not specified.

For this reason, use this option only for tuning purposes.

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