Java Garbage Collection Timeline Report
The garbage collection feature in JVM scans the heap memory and empties the memory space occupied by objects that have remained unused or have not been referenced for a long time. Garbage collection runs automatically at frequent intervals and improves application performance by optimizing the memory. The Java Garbage Collection Timeline Report displays the memory size cleared by the memory managers at a particular time frame in the selected profile and jvm environment.
The information in the report is displayed in two sections:
- A line graph displaying the memory used by global and scavenge memory managers.
- A data table with detailed information about each memory manger.
To access the report
- In the myStrobe window, select a Performance Profile. For more information, see Creating performance profile.
- Click
and select Java >JVM Name-PID from the menu.
- From the list of available Strobe for Java report, select the Java Garbage Collection Report.
The report is generated in the form of a line graph. - Click anywhere on the thread line in the plot area to view the CPU time.
In the line graph:
- The x (horizontal) axis displays time stamps based on the specified time interval.
- The y (vertical) Size in Mb axis represents the memory size (in megabytes).
- The blue line represents the memory used by the scavenge Memory Manager, which collects new objects.
- The green line represents memory used by the global Memory Manager, which collects old objects.
You can perform the following actions on the line graph:
- To view the exact object memory value at a point, hover over that point.
- To zoom in, click and drag the line at a data point.
- To zoom out, double-click the line.
- To create and save notes on the observations you make in the report, click
.
Data table
When you select a specific data point of either of the two memory managers on the graph, the corresponding information gets displayed in the data table.
To view or hide details about a specific thread, click 
and 
.
The data table consists of the following fields:
Field | Description |
|---|---|
Memory Used | Indicates the memory space occupied |
Memory Manager Name | Indicates the name of memory manager, global or scavenge |
Timestamp | Displays the date and time |
Average GC Time | Displays the average time taken by each Garbage Collection cycle in microseconds |
Accumulated GC Time | Indicates the cumulative time take by the JVM in garbage collection |
Accumulated Memory Freed | Indicates the cumulative memory space emptied by the JVM after garbage collection |
Accumulated GC Count | Indicates the cumulative count of Garbage Collection cycles in the jvm environment |