How to Check Java Heap

Just some quick tips on checking the java heap.

You can get the process id from ps or use jps -l to list it.

jmap, jstat and jconsole are very good tools for finding out more about your jvm.

Check Heap size and details memory usage.

• jmap -heap <jvm proc id> 

Check Max Settings

• # ./jmap -heap 14272 |grep Max
• Attaching to process ID 14272, please wait...Debugger attached successfully.Server compiler detected.JVM version is 23.3-b01   MaxHeapFreeRatio = 70   MaxHeapSize      = 1610612736 (1536.0MB)   MaxNewSize       = 17592186044415 MB   MaxPermSize      = 536870912 (512.0MB)

Other Java Memory Tips 

Check Java Process ID 

•  ./jps -l 

Use jstat to See GC 

• ./jstat -gcutil <jvm proc> 10 1 

Output Info 

Here is a list of acronyms used in the above output. 

• S0 Survivor space 0 
• S1 Survivor space 1 
• E Eden Generation 
• O Old Generation 
• P Permanent Generation 
• YGC Young GC Count 
• YGCT Young GC time 
• FGC Full GC Count 
• FGCT Full GC time 
• GCT Any GC time 

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