Unable to increase the java heap size

Question

I'm using 64bit Ubuntu and java vm 64 bit version.

I have 8GB ram.

I am unable to change the java heap size to 4096m, not even 2048m.

I tried these things:

uname -i

Output:

x86_64

java -version

OUTPUT:

openjdk version "11.0.4" 2019-07-16

OpenJDK Runtime Environment (build 11.0.4+11-post-Ubuntu-1ubuntu218.04.3)

OpenJDK 64-Bit Server VM (build 11.0.4+11-post-Ubuntu-1ubuntu218.04.3, mixed mode, sharing)

When I tried to change the heap size:

java -Xmx:4096m

OUTPUT

Invalid maximum heap size: -Xmx:4096m

Error: Could not create the Java Virtual Machine.

Error: A fatal exception has occurred. Program will exit.

The same for 2048m size

java -XX:+PrintFlagsFinal -version | grep HeapSize

OUTPUT:

size_t ErgoHeapSizeLimit                        = 0                                         {product} {default}
size_t HeapSizePerGCThread                      = 43620760                                  {product} {default}
size_t InitialHeapSize                          = 130023424                                 {product} {ergonomic}
size_t LargePageHeapSizeThreshold               = 134217728                                 {product} {default}
size_t MaxHeapSize                              = 2067791872                                {product} {ergonomic}
uintx NonNMethodCodeHeapSize                   = 5835340                                {pd <p>product} {ergonomic}
uintx NonProfiledCodeHeapSize                  = 122911450                              {pd <p>product} {ergonomic}
uintx ProfiledCodeHeapSize                     = 122911450                              {pd <p>product} {ergonomic}
openjdk version "11.0.4" 2019-07-16
OpenJDK Runtime Environment (build 11.0.4+11-post-Ubuntu-1ubuntu218.04.3)
OpenJDK 64-Bit Server VM (build 11.0.4+11-post-Ubuntu-1ubuntu218.04.3, mixed mode, sharing)

Answer 1

First check the default value:

java -XshowSettings:vm

then you'll need to edit the settings file for the JVM: sudo vim /etc/profile Add this to the beginning of the file:

export _JAVA_OPTIONS=-Xmx(size you want in here)m 

Press ESC, type :wq and press Enter

After that you can execute the same command to check if the size was changed:

java -XshowSettings:vm

Answer 2

The correct format is:

java -Xmx4G -jar test.jar

You can test it with:

java -Xmx4G -XX:+PrintFlagsFinal -version | grep HeapSize