CODEWITHSUNDEEP
java
Proyb2
Proyb2

Reputation: 993

limit java program with specify amount of memory

How do I set java program from consumption large amount of memory? Does constantly System.out.println increase in memory consumption?

I have profiling using VisualVM, I don't quite understanding on how to fix some part of the code.

Upvotes: 2

Views: 2142

Answers (2)

extraneon
extraneon

Reputation: 23980

The way to consume massive amounts of memory is by retaining objects. That is, keep them alive after you're done with them. A cache with infinite size for instance could do that.

But even then the JVM is limited to the memory assigned to it (on for instance the command line), it can never go beyond PermGenSize + HeapSize. If you hit that threshold java will stop with an OutOfMemoryError.

Using a large amount of memory according to the profiler does not mean that your program is actually needing that amount of memory. It can also be that the garbage collector has not yet run, or decided it doesn't need to run all that aggressively because there is still enough memory left.

Upvotes: 0

moinudin
moinudin

Reputation: 138497

Use the -Xmxn flag, e.g. java -Xmx100m foo to limit foo to 100MB.

-Xmxn

Specify the maximum size, in bytes, of the memory allocation pool. This value must a multiple of 1024 greater than 2MB. Append the letter k or K to indicate kilobytes, or m or M to indicate megabytes. The default value is chosen at runtime based on system configuration. For more information, see HotSpot Ergonomics

Examples:

-Xmx83886080

-Xmx81920k

-Xmx80m

Worth a read: http://javahowto.blogspot.com/2006/06/6-common-errors-in-setting-java-heap.html

Constantly using System.out.println() should not increase memory usage. Each call is independent of the next and they won't build up a stash of used memory.

Upvotes: 5

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