Java garbage collector's parallel old collector

Parallel Old collectors are JAVA one of the garbage collectors in a virtual machine. like the Serial old collector, it works in the older era of JAV virtual machines. This garbage collector uses multithreading and the "mark-and-organize" algorithm. It is only available in JDK 1.6 .

in the focus on throughput and CPU resource-sensitive situations, they can be given priority Parallel Scavenge Plus Parallel Old Collector.

1 , run code

Package COM.GC;

Import java.util.ArrayList;

Import java.util.List;

/**

 * simple. JAVA Virtual machine Memory Reclamation , parallel old Use of Collectors

 * Parameters: -xms30m-xmx60m-xmn10m-xx:+useparalleloldgc-xx:+printgcdetails

* @author Fan Fangming

*/

public class Easyparallelold {

Public byte[] PlaceHolder =new byte[64 * 1024x768];// placeholder

public static Voidmain (string[] args) throws exception{

Outofmemorybyexpansionsize ();

}

private static Voidoutofmemorybyexpansionsize () throws exception{

List<easyparallelold>list = new arraylist<easyparallelold> ();

while (true) {

easyparalleloldserial = new Easyparallelold ();

List.add (serial);

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

}

}

}

2 , Parameters

-xms30m-xmx60m-xmn10m-xx:+useparalleloldgc-xx:+printgcdetails

-xms30m JVM Minimum 30M

-xmx100m JVM Maximum 100M

-xmn10m Cenozoic Fixed 10M

-xx:+ USEPARALLELOLDGC corresponding parallel scavenge +parallel old Collecting Device

-xx:+printgcdetails Print Details GC

3 , running results

...

[Full GC [psyounggen:3394k->3394k (6848K)] [paroldgen:50664k->50664k (51200K)]54058k->54058k (58048K) [ PSPERMGEN:2084K->2084K (12288K)], 0.0043610 secs][times:user=0.00 sys=0.00, real=0.00 secs]

[Full GC [psyounggen:3394k->3394k (6848K)] [paroldgen:50728k->50728k (51200K)]54122k->54122k (58048K) [ PSPERMGEN:2084K->2084K (12288K)], 0.0071480 secs][times:user=0.00 sys=0.00, real=0.01 secs]

[Full GC [psyounggen:3394k->3394k (6848K)] [paroldgen:50792k->50792k (51200K)]54186k->54186k (58048K) [ PSPERMGEN:2084K->2084K (12288K)], 0.0061676 secs][times:user=0.00 sys=0.00, real=0.01 secs]

[Full GC [psyounggen:3394k->3394k (6848K)] [paroldgen:50856k->50856k (51200K)]54250k->54250k (58048K) [ PSPERMGEN:2084K->2084K (12288K)], 0.0047575 secs][times:user=0.00 sys=0.00, real=0.00 secs]

[Full GC [psyounggen:3394k->3394k (6848K)] [paroldgen:50920k->50920k (51200K)]54314k->54314k (58048K) [ PSPERMGEN:2084K->2084K (12288K)], 0.0044603 secs][times:user=0.00 sys=0.00, real=0.00 secs]

[Full GC [psyounggen:3394k->3394k (6848K)] [paroldgen:50984k->50984k (51200K)]54378k->54378k (58048K) [ PSPERMGEN:2084K->2084K (12288K)], 0.0041311 secs][times:user=0.00 sys=0.00, real=0.00 secs]

[Full GC [psyounggen:3394k->3394k (6848K)] [paroldgen:51048k->51048k (51200K)]54442k->54442k (58048K) [ PSPERMGEN:2084K->2084K (12288K)], 0.0042710 secs][times:user=0.00 sys=0.00, real=0.00 secs]

[Full GC [psyounggen:3394k->3394k (6848K)] [paroldgen:51112k->51112k (51200K)]54506k->54506k (58048K) [ PSPERMGEN:2084K->2084K (12288K)], 0.0044147 secs][times:user=0.00 sys=0.00, real=0.00 secs]

[Full GC [psyounggen:3394k->3394k (6848K)] [paroldgen:51176k->51176k (51200K)]54570k->54570k (58048K) [ PSPERMGEN:2084K->2084K (12288K)], 0.0044082 secs][times:user=0.00 sys=0.00, real=0.00 secs]

[Full GC [psyounggen:3394k->3394k (6848K)] [paroldgen:51176k->51176k (51200K)]54570k->54570k (58048K) [ PSPERMGEN:2084K->2084K (12288K)], 0.0044738 secs][times:user=0.00 sys=0.00, real=0.01 secs]

Exception in thread "main" Java.lang.OutOfMemoryError:Java heap space

atcom.gc.easyparnew.<init> (easyparnew.java:12)

atcom.gc.EasyParNew.outOfMemoryByExpansionSize (easyparnew.java:39)

Atcom.gc.EasyParNew.main (easyparnew.java:14)

Heap

Psyounggen total 6848K, used 3456K [0x0ad30000, 0x0b730000, 0x0b730000)

Eden Space 3456K, 100% used [0x0ad30000,0x0b090000,0x0b090000)

From space 3392K, 0% used [0x0b090000,0x0b090000,0x0b3e0000)

To space 3392K, 0% used[0x0b3e0000,0x0b3e0000,0x0b730000)

Paroldgen total 51200K, used 51176K [0x07b30000, 0x0ad30000, 0x0ad30000)

Object Space 51200K, 99% used [0x07b30000,0x0ad2a0a0,0x0ad30000)

Pspermgen total 12288K, used 2105K [0x03b30000, 0x04730000, 0x07b30000)

Object Space 12288K, 17% used [0x03b30000,0x03d3e4a8,0x04730000)

4 , and serial Old Differences in Collectors

serial Old collectors are serialized for garbage collection, while Parallel Old collectors are garbage collected in parallel.

[Full GC [psyounggen:3394k->3394k (6848K)] [paroldgen:51048k->51048k (51200K)]54442k->54442k (58048K) [ PSPERMGEN:2084K->2084K (12288K)], 0.0042710 secs][times:user=0.00 sys=0.00, real=0.00 secs]

And

[GC [defnew:9108k->966k (9216K), 0.0049332 secs][tenured:46824k->46893k (46920K), 0.0033687 secs] 47800k-> 47790K (56136K), [perm:2086k->2086k (12288K)], 0.0084489 secs] [times:user=0.02 sys=0.00,real=0.01 secs]

Paroldgen said is parallel old in the age of recycling;

Tenured means that serial old is recycled in the older years.

Java garbage collector's parallel old collector