1. Problems and phenomena

There is a dump file with a size of 14G, which is analyzed by the jhat tool

error out of memory

Reading from gl.hprof...
Dump file created Wed Jun 08 17:56:28 CST 2022
Exception in thread "main" java.lang.OutOfMemoryError: Java heap space
	at java.util.Hashtable.addEntry(Hashtable.java:436)
	at java.util.Hashtable.put(Hashtable.java:477)
	at com.sun.tools.hat.internal.model.Snapshot.addHeapObject(Snapshot.java:166)
	at com.sun.tools.hat.internal.parser.HprofReader.readInstance(HprofReader.java:744)
	at com.sun.tools.hat.internal.parser.HprofReader.readHeapDump(HprofReader.java:491)
	at com.sun.tools.hat.internal.parser.HprofReader.read(HprofReader.java:275)
	at com.sun.tools.hat.internal.parser.Reader.readFile(Reader.java:92)
	at com.sun.tools.hat.Main.main(Main.java:159)
[root@nccztsjb-node-27 data]# netstat -ntlp

I changed a host with 32G memory, and the execution still reported an error of memory overflow. I was thinking about whether the jhat tool itself has a memory limit…  

2. Solution

Increase the memory used by jhat

jhat -J-mx20g gl.hprof

Use -J to specify the size of the memory. [-J-mx20g]