How to print out Java jvm memory use for debugging purposes?

Question

I have a large Java app that uses massive amounts of memory at times and I would like to monitor this at intervals to see if heap or permgen limits are reached or have gotten near to them.

How can I print out the most relevant pieces of mem usage information using java?

Lauri Piispanen · Accepted Answer · 2018-10-23 06:51:17Z

20

Here's a snippet from a piece of code we have that periodically logs the memory usage of our app:

import java.lang.management.GarbageCollectorMXBean
import java.lang.management.ManagementFactory
import java.lang.management.MemoryPoolMXBean
import java.lang.management.MemoryUsage

log("Heap", ManagementFactory.getMemoryMXBean().getHeapMemoryUsage());
log("NonHeap", ManagementFactory.getMemoryMXBean().getNonHeapMemoryUsage());
List<MemoryPoolMXBean> beans = ManagementFactory.getMemoryPoolMXBeans();
for (MemoryPoolMXBean bean: beans) {
    log(bean.getName(), bean.getUsage());
}

for (GarbageCollectorMXBean bean: ManagementFactory.getGarbageCollectorMXBeans()) {
    log(bean.getName(), bean.getCollectionCount(), bean.getCollectionTime());
}

edited Oct 23, 2018 at 6:51

answered Mar 27, 2012 at 10:26

Lauri Piispanen

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2 Comments

Lauri Piispanen Over a year ago

Likely copy-paste snafu from editing the original source. Fixed! 👍

lucasvc Over a year ago

Could you please add how the method log works or specify if it comes from any library?

Jakub Zaverka · Accepted Answer · 2012-03-27 10:33:46Z

1

You can try visualVM, a Java profiler that goes with every JDK. You will find it in the "bin" folder.

answered Mar 27, 2012 at 10:33

Jakub Zaverka

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1 Comment

Jan Wikholm Over a year ago

I know of VisualVM and have used it for when I am actively debugging a problem as it is happening. But some problems occur during nightly runs which means I need to log them somewhere to process them later. I could of course leave the VisualVM app open for the night, but it is not quite the long-term solution I am looking for, since logs are permanent and accessible by all users on the system and not tied to my computer :)

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