January 2018
Intermediate to advanced
350 pages
9h 7m
English
Content preview from Java EE 8 High Performance
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Heap dump
Sometimes, you will need to get a heap dump to investigate what is in memory and why the GC runs so often or for so long. To do so, the JDK provides a tool called jmap that allows you to take a dump from the Java PID:
jmap -dump:format=b,file=/path/to/dump.hprof <PID>
This command will stop the application (a bit like a stop the world pause) and write all the instances into the configured file. Opening the output with jvisualvm will enable you to investigate the instances, and, in particular, the number of instances and the corresponding allocating size.
Here is what it can look like:
Normally, you should mainly see JVM classes such ...
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.