Viewing Heap Dump Information

Prerequisites

A real-time profiling task has been created and is in progress.

Procedure

1. In the Task/Report List area of the Java Profiler page, click the name of the analysis task under Real-Time Profiling.

   The Overview tab page is displayed.

2. Click the Memory tab and then the Start Heap Dump button.
   The heap dump histogram is generated. See Figure 1. For details about the parameters, see Table 1.

   

   • You can click in the upper right corner of the page to save the snapshot of the current page to the Snapshot tab page.
   • Only one snapshot needs to be saved for one heap dump. Multiple snapshots can be saved for multiple heap dumps for snapshot comparison.
   • You can enter a class name in the search box in the upper right corner of the page to quickly filter data.
   • You can click in the upper right corner of the page to save the current memory analysis report. The saved report contains the Heap Dump and Report Information tab pages. You can view or download the report in Data List on the home page.

   Figure 1 Heap dump (histogram)
   

   Table 1 Parameters in the histogram

   Parameter	Description
   Class name	The following types of class names are supported: Class name (displayed when instances are class instances) Instance ID GC root information (displayed when the instance is a GC root)
   Number of Instances	Number of instances after garbage collection.
   Shallow Heap Size	Size of the shallow heap occupied by the instances after garbage collection.
   Retained Heap Size	Size of the retained heap occupied by the instances after garbage collection.

   Click before a class name in Figure 1.

   Choose Shortest Common Path from GC Roots to Objects to generate the shortest common path. See Figure 2. For details about the parameters, see Table 2.

   

   You can select extended information in the upper right corner of the page.

   • Soft Ref: indicates soft reference. Softly referenced objects are included in the calculation of the reference path.
   • Weak Ref: indicates weak reference. Weakly referenced objects are included in the calculation of the reference path.
   • Phantom Ref: indicates phantom reference. Phantom reference objects are included in the calculation of the reference path.
   Figure 2 Shortest common path from GC roots to objects
   

   Table 2 Parameters on the Shortest Common Path from GC Roots to Objects page

   Parameter	Description
   Class	The following types of class names are supported: Class name (displayed when instances are class instances) Instance ID GC root information (displayed when the instance is a GC root)
   Referenced Instances	Number of referenced instances after garbage collection.
   Shallow Heap Size of the Current Object	Size of the shallow heap occupied by the current object after garbage collection.
   Shallow Heap Size of Referenced Instances	Size of the shallow heap occupied by the referenced instances after garbage collection.
   Reserved Heap Size of the Current Object	Size of the retained heap occupied by the current object after garbage collection.

   Choose List All Objects of the Class to list all objects. See Figure 3. For details about the parameters, see Table 3.

   Figure 3 Listing all objects of the class
   

   Table 3 Parameter description

   Parameter	Description
   Class Name	The following types of class names are supported: Class name (displayed when instances are class instances) Instance ID GC root information (displayed when the instance is a GC root)
   Shallow Heap Size	Size of the shallow heap occupied by the instances after garbage collection.
   Retained Heap Size	Size of the retained heap occupied by the instances after garbage collection.

3. Select Dominator tree from the Display drop-down list.

   Heap dump information is displayed in a tree structure. See Figure 4.

   Figure 4 Heap dump (dominator tree)
   

   Click before a class name in Figure 4.

   Choose Path from Objects to GC Roots to generate a path diagram. See Figure 5.

   Figure 5 Path from objects to GC roots