JVM Tuning-Initialize the size of the space configuration

We get the active data size and we can configure our initialization space based on the active data.

here is a section of our application in the stabilization phase FULLGC . The generated code is at the end.

1 , active data Examples

[Full gc[psyounggen:64k->0k (4416K)] [psoldgen:51352k->51352k (56768K)]51416k->51352k (61184K) [Pspermgen: 2085k->2085k (12288K)], 0.0026228 secs][times:user=0.00 sys=0.00, real=0.00 secs]

Psyounggen : Cenozoic Situation

Psoldgen : The old age situation, occupy space 51352K , 51M , this is an active data situation in the old age.

Pspermgen : Permanent belt condition, space occupied 2085K , 2M , it is a permanent band of active data size.

2 , common experience parameters

2.1 old age Size

   Java The initialization and maximum values of the heap size (via -xms Span style= "Color:rgb (51,51,51)" >-xmx option to specify) should be the size of the old age of the active object 3 to 4

The above GC record shows that the old age size is 51M, then the corresponding initial and maximum values are at 153M to 204M between; -xms153m–xmx204m

2.2 Permanent Generation size

         Another rule is that the initial and maximum values of the permanent band (-xx:permsizeand the-xx:maxpermsize) should be permanent with the active object size1.2to the1.5times. In the aboveFULLGCafter that, the permanent occupancy space is2M. Therefore, the recommended size for a permanent generation is2.4Mto the3M,that can be set to-xx:permsize=3m-xx:maxpermsize=3m (1.5Times).

2.3 Cenozoic Size

The Cenozoic space should be 1 to 1.5 times the size of the active object in the old age . So in this example, the Cenozoic size can be set to 51M to 76M.

So the final parameter is:-xms200m-xmx200m-xmn60m-xx:permsize=3m-xx:maxpermsize=3m-xx:+useparallelgc-xx : +printgcdetails

After use,thefullgc is no longer present, and there is no memory overflow problem.

3 , calculate active data (simulate Full GC ) 's Source code

PACKAGECOM.GC;

Importjava.util.ArrayList;

Importjava.util.List;

/**

 * a simple simulation FULLGC To calculate the active data size

 * Parameters: -xms30m-xmx60m-xx:+useparallelgc-xx:+printgcdetails

* @author Fan Fangming

*/

Publicclass Easyactivedata {

Public byte[] PlaceHolder = new byte[1024* [1024x768]; placeholder 1M

public static void Main (string[] args) throws exception{

ActiveData ();

}

private static void ActiveData () throwsexception{

List<easyactivedata>list_a = new arraylist<easyactivedata> ();

List<easyactivedata>list_b = new arraylist<easyactivedata> ();

for (int j=0; J < 25;j + +) {

easyactivedataserial = new Easyactivedata ();

List_a.add (serial);

}

Thread.Sleep (+);// Pause under

for (int j=0; J < 30;j + +) {

easyactivedataserial = new Easyactivedata ();

List_b.add (serial);

}

Thread.Sleep (+);// Pause under

while (true) {

easyactivedataserial = new Easyactivedata ();

serial = List_a.get (0);

serial = NULL;

Serial =list_b.get (0);;

Thread.Sleep (+);// Pause Ten milliseconds

}

}

}

Operating parameters

-xms30m Boot Memory

-xmx60m Maximum Memory

-XX:+USEPARALLELGC Choice of garbage collection method

-xx:+printgcdetails Print GC Detail

4 , running results

...

[Full GC [psyounggen:64k->0k (4416K)] [psoldgen:51352k->51352k (56768K)]51416k->51352k (61184K) [Pspermgen: 2085k->2085k (12288K)], 0.0026228 secs][times:user=0.00 sys=0.00, real=0.00 secs]

[GC [psyounggen:4098k->48k (4416K)] 55450k->55496k (61184K), 0.0038392 secs] [times:user=0.00 sys=0.00, real=0.00 secs]

[Full GC [psyounggen:48k->0k (4416K)] [psoldgen:55448k->55448k (56768K)]55496k->55448k (61184K) [Pspermgen: 2085k->2085k (12288K)], 0.0025522 secs][times:user=0.02 sys=0.00, real=0.00 secs]

[Full GC [psyounggen:4098k->0k (4416K)] [psoldgen:55448k->56472k (56768K)]59546k->56472k (61184K) [Pspermgen : 2085k->2085k (12288K)], 0.0043092 secs]

...

JVM Tuning-Initialize the size of the space configuration