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The Status Monitor's History Page

The History Page is a plug-in page for the Status Monitor that displays a histogram of JNIPort activity.

Status Monitor showing History page

The graph is updated at intervals controlled by the 'View⇒Update interval⇒' sub-menu (which is initially set from the JVM's #statusMonitorSettings configuration settings). The traces are labelled by the “legend” (which can be turned off from the View menu), they are:

Local refs (solid blue)

The number of “local” references to Java objects that were wrapped by JNIPort objects at the sampling time.

Global refs (solid dark green)

The number of “global” references to Java objects that were wrapped by JNIPort objects at the sampling time.

The distinction between local and global is an internal matter (reflecting one of the odd features of JNI). Local references are not used at all if JNIPort has been configured to support callbacks.

Refs created per sec (light green line)

The rate at which JNIPort wrapped references to Java objects over the period since the previous sampling time.

Refs released per sec (pink line)

The rate at which JNIPort discarded and released references to Java objects over the period since the previous sampling time. (Since references are released by finalisation, this is a measure of how much work JNIPort is giving the finaliser to do.)

Callbacks per sec (yellow line)

The rate at which JNIPort serviced callbacks over the period since the previous sampling time.


Copyright © Chris Uppal, 2003-2005

Java, JNI (probably), JVM (possibly), and God knows what else, are trademarks of Sun Microsystems, Inc.