Investigating Performance issue in Live Environment

1. Take a thread dump when the issue is with CPU
2. Go for heap dump if this is affecting high memory usage
3. Replicate similar load testing in some other environment.
4. Do performance Baselining/Benchmarking.

List of java process running :

jcmd -l

Java Histogram : To get java object statistics 

jmap -histo <process_id> > histogram_current_time.txt

*Strings are not part of object size in the above results

Get Threaddump:

jstack -l <pid>

Sometimes threads are stuck and other threads are blocked , this causes shooting up heap uses

HeapDump:

jmap -dump:format=b,file=<relative>/heap.bean

Profiling Tool:
Jconsole:
Open jconsole
adding remote host:port and credential
It will show dashboards for heap memory, thread, class,cpu usage, VM summary,Mbeans
Mbeans is useful to do lot of java exposed operation
-By seeing the memory usage diff between before and after an operation, the increase in memory tells the memory utilisation in an activity or set of objects.
-You can trigger GC run to clean up unused objects.

visualVM:
Add new jmx connection:hostname:port/credentials
we can take snapshot, do cpu sampling
Both the above tools allow perform GC,
visual VM has option to get heap dump, it saves on the m/c java is running.

JVisualVM

- jvosualvm, JDK provided tool