7.12.1 -XX:ExplicitMemoryAutoReclaimTargetBlockRatio

Description

-XX:ExplicitMemoryAutoReclaimTargetBlockRatio is used when the size of the used Explicit heap area continues to increase, even when automatic release processing is repeatedly executed after Explicit heap tuning has been performed and the objects to be allocated to the Explicit heap by the automatic placement functionality have been selected. In the automatic release processing for Explicit memory blocks, the Explicit memory blocks to be automatically released are selected. However, depending on the reference relationships among objects, you might not be able to delete certain objects just by specifying one Explicit memory block. Instead, you might need to specify multiple Explicit memory blocks. This option can be used to increase the number of memory blocks that are selected to be released.

Specify the maximum release rate that can be set in the automatic release processing of the explicit memory management functionality. The release rate is the ratio of the amount of the heap area that is actually released by automatic release processing, to the amount selected during the automatic release processing.

The explicit memory management functionality uses the previous release rate for the automatic release processing to determine the number of memory blocks to be selected for release. Based on this release rate, the number of memory blocks to be selected for release is adjusted according to the inflow amount of the Explicit heap. As a result, increases in the amount of used Explicit heap area can be prevented. Note, however, that if the number of memory blocks selected for release increases, the automatic release processing takes more time. Similar to the case of full GC, while the automatic release processing is running, the execution of applications stops. For this reason, an upper limit is set for the number of memory blocks selected for release, so that the automatic release processing does not take an excessively long time.

If you specify 0, the upper limit is the same as the limit that is set when this option is omitted. If you specify 100, the upper limit of the release rate that was set in the previous automatic release processing is increased to the maximum value. However, because of the behavior of the automatic release processing, even if you specify 100, this does not mean that all objects in the Explicit heap become targets of automatic release processing.

Prerequisite options

• -XX:+HitachiUseExplicitMemory

• -XX:+HitachiExplicitMemoryAutoReclaim

Syntax

-XX:ExplicitMemoryAutoReclaimTargetBlockRatio=integer_value

Specifiable values

integer_value

Type: Integer

Specify a value (as a percentage) from 0 to 100.

Default value

If the definition item is omitted:

-XX:ExplicitMemoryAutoReclaimTargetBlockRatio=0

If the value is omitted:

The following message is output to the standard error and Java VM is terminated with return code 1.

Improperly specified VM option 'ExplicitMemoryAutoReclaimTargetBlockRatio='
Error:  Could not create the Java Virtual Machine.
Error:  A fatal exception has occurred. Program will exit.