-Xmx -Xms and paging

I have a 64 bit windows box with 2gigs.
The operating system takes 600 mgs.
If I do this:
-Xmx2000m -Xms512m
will it page (ie use virtual memory) only when it needs to and then stop using virtual memory when memory consumption goes back down?
In other words I have an algo that can spike in terms of memory, but I would like to know if after one of these spikes it can ever stop paging, or will the vm get in this case its 2gig of memory and the os will presume that it has to page?
thanks.

will it page (ie use virtual memory) only when it
needs to and then stop using virtual memory when
memory consumption goes back down?
Depends on the JVM implementation.
Some will release memory no longer needed after garbage collection, some will not, some may be smart enough to keep track of memory requirements over time and try to predict if that memory will be needed again soonish and keep it if so.
Whether it will page or not depends on your operating system and available hardware, not the JVM.

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<j2se version="1.4+" initial-heap-size="80m" max-heap-size="80m"/>
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There is a whole list ov vm-args considered "safe" by java web start listed in the developers guide at:
http://java.sun.com/j2se/1.5.0/docs/guide/javaws/developersguide/syntax.html#resources
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is the command line command.
But after I start the app server, when I look at the Window's task manager the java. exe has about 50M memory usage. Is there something wrong???
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hi all, i got a problem by allocating a very great boolean array.
first of all, here is my testcode:
public static void main(String[] args) {
          boolean[] testfield = new boolean[70000000];
          while(true){
          //NOP
     }as you see, i try to allocate an array with 70.000.000 boolean values - as 1 boolean may be represented as at least one physical bit we calculate the total amount of needed RAM-Space:
70.000.000 bit / 8 = 8750000 byte
8.750.000 byte = 8.75 MByte
My System ist WinVista Ultimate 64-bit running on a Quadcore T2200 with 2GB-DDR3 RAM
Looking in my Vista Ressourcemanager shows, that eclipse.exe reserves about 1.023 Mbyte....
As IDE I use eclipse
my eclipse.ini looks as follows:
-showsplash
org.eclipse.platform
--launcher.XXMaxPermSize
256M
-vmargs
-Dosgi.requiredJavaVersion=1.5
-Xms512m
-Xmx1024m
-XX:PermSize=512mby using following VMCommand "-XX:+PrintGCDetails" and running the above code the output displays:
[GC [DefNew: 180K->63K(960K), 0.0008311 secs][Tenured: 43K->107K(4096K), 0.0060371 secs] 180K->107K(5056K), 0.0069249 secs] [Times: user=0.00 sys=0.00, real=0.01 secs]
[Full GC [Tenured: 107K->105K(60544K), 0.0044835 secs] 107K->105K(61504K), [Perm : 17K->16K(12288K)], 0.0045553 secs] [Times: user=0.00 sys=0.00, real=0.00 secs]
Exception in thread "main" java.lang.OutOfMemoryError: Java heap space
     at termain.main(termain.java:15)
Heap
def new generation   total 4544K, used 163K [0x246a0000, 0x24b80000, 0x24b80000)
eden space 4096K,   4% used [0x246a0000, 0x246c8fe0, 0x24aa0000)
from space 448K,   0% used [0x24aa0000, 0x24aa0000, 0x24b10000)
to   space 448K,   0% used [0x24b10000, 0x24b10000, 0x24b80000)
tenured generation   total 60544K, used 105K [0x24b80000, 0x286a0000, 0x286a0000)
   the space 60544K,   0% used [0x24b80000, 0x24b9a420, 0x24b9a600, 0x286a0000)
compacting perm gen total 12288K, used 16K [0x286a0000, 0x292a0000, 0x2c6a0000)
   the space 12288K,   0% used [0x286a0000, 0x286a41c0, 0x286a4200, 0x292a0000)
    ro space 8192K, 62% used [0x2c6a0000, 0x2cba2ba0, 0x2cba2c00, 0x2cea0000)
    rw space 12288K, 52% used [0x2cea0000, 0x2d4e88e0, 0x2d4e8a00, 0x2daa0000)so can anyone tell me please, how i manage to allocate bigger arrays? or where at least is the problem?
Originally i was thinking like that way: Integer.MAXVALUE = (2^32)-1
=> biggest index an array can have
=> biggest allocation possible with ints weights (((2^32)-^1)/8)/1000*1000 = (round) 537 MByte < 2GByte => everything fine .... but it seems like not :-(
When i try to allocate 60.0000.000 it works fine....but that is far not enough :-&
thank you very much for your helping answers!

The Sun Java virtual machine stores booleans as bytes, not bits, so for an array of 70 million booleans you need 70 million bytes, plus 8 bytes for the object header, and 4 bytes for the array length.
I suspect that your eclipse.ini controls the JVM running the Eclipse IDE, not the JVM running your application. Note that in the -XX:+PrintGCDetails output at the end, it shows you running out of memory with 4MB of young generation and 60MB of old generation. That's the default configuration, as if you hadn't specified -Xms and -Xmx.
The array of 60 million booleans only requires 60 million bytes (plus overhead), which fits in the default old generation.
I think you need to put the -Xms and -Xmx in the same place you put the -XX:+PrintGCDetails, since that does seem to display information about the JVM running your application, not the JVM running Eclipse.

Why are -Xms and -Xmx limits so small?

On a Win XP machine with 3GB of installed memory, the limits for -Xms and -Xmx are 1GB. My knapsack program works for small inputs (< 20 objects). But for real world problems it crashes immediately with an out-of-memory error. What possible harm could it do to allow a Java user to increase -Xms and -Xmx to 2 or 3 GB, or even larger? I would not care if it thrashed, if it finally came up with a good answer.

CHE22 wrote:
CHE22 wrote:
On a Win XP machine with 3GB of installed memory, the limits for -Xms and -Xmx are 1GB.
tschodt wrote:
How did you arrive at that?
By reading this:
http://java.sun.com/j2se/reference/whitepapers/memorymanagement_whitepaper.pdf.
I guess you are referring to
Automatic Selection of Collector, Heap Sizes, and Virtual Machine
A server-class machine is defined to be one with
2 or more physical processors and
2 or more gigabytes of physical memory
13 Ergonomics - Automatic Selections and Behavior Tuning Sun Microsystems, Inc.
This definition of a server-class machine applies to all platforms, with the exception of 32-bit platforms running a version of the Windows operating system.
On machines that are not server-class machines, the default values for JVM, garbage collector, and heap sizes are
the client JVM
the serial garbage collector
Initial heap size of 4MB
Maximum heap size of 64MB
On a server-class machine, the JVM is always the server JVM unless you explicitly specify the -client
command line option to request the client JVM. On a server-class machine running the server JVM, the default
garbage collector is the parallel collector. Otherwise, the default is the serial collector.
On a server-class machine running either JVM (client or server) with the parallel garbage collector, the default initial and maximum heap sizes are
Initial heap size of 1/64th of the physical memory, up to 1GB. (Note that the minimum initial heap size is 32MB, since a server-class machine is defined to have at least 2GB of memory and 1/64th of 2GB is 32MB.)
Maximum heap size of 1/4th of the physical memory, up to 1GB.
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Shared memories inside of pool 40
Key:       42 Size:    17792992 ( 17.0 MB) DB TTAB buffer
Key:       43 Size:    53606392 ( 51.1 MB) DB FTAB buffer
Key:       44 Size:     8550392 (   8.2 MB) DB IREC buffer
Key:       45 Size:     7014392 (   6.7 MB) DB short nametab buffer
Key:       46 Size:       20480 (   0.0 MB) DB sync table
Key:       47 Size:    10241024 (   9.8 MB) DB CUA buffer
Key:       48 Size:      300000 (   0.3 MB) Number range buffer
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Key:        4 Size:      523048 (   0.5 MB) statistic area
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Key:        7 Size:       14838 (   0.0 MB) Update task administration
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Key:        9 Size:   134217828 ( 128.0 MB) Roll buffer
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Key:       19 Size:   119850000 ( 114.3 MB) Table-buffer
Key:       41 Size:    25010000 ( 23.9 MB) DB statistics buffer
Key:       63 Size:      409600 (   0.4 MB) ICMAN shared memory
Key:       64 Size:     4202496 (   4.0 MB) Online Text Repository Buf.
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Nr of operating system shared memory segments: 16
Shared memory resource requirements estimated
================================================================
Total Nr of shared segments required.....:         16
System-imposed number of shared memories.:       1000
Shared memory segment size required min..: 692224000 ( 660.2 MB)
System-imposed maximum segment size......: 35184372088832 (33554432.0 MB)
Swap space requirements estimated
================================================
Shared memory....................: 1654.8 MB
..in pool 10 328.6 MB,   58% used
..in pool 40 143.3 MB,   30% used
..not in pool: 1174.1 MB
Processes........................: 413.4 MB
Extended Memory .................: 6144.0 MB
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Process local heaps, worst case..: 3814.7 MB
Total, worst case requirement....: 21882.9 MB
Errors detected..................:    0
Warnings detected................:    3

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Have you seen the part of the example configs where it talks
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Hi,
i have the following doubts regarding the jdbc and paging please clarify me...
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Hi,
I have a problem with deploy bpel process , I get an error "java.lang.OutOfMemoryError: PermGen Space" several sources of information tells me that I have to change some parameters in the file "<ORACLE_HOME> / opmn / conf / opmn.xml" but I doubt some of the parameters, what is the difference between Xms and ms?
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I know what they are supposed to do, but am unable to see any tangible results from setting them...

On my machine they do exactly what they're supposed to...that is, to set the initial and max memory available for a program. I wrote two programs to test this :
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public void main(String args[]) {
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public static void main(String args[]) throws Exception {
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From the documentation:
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If I increate the values to a higher number it will create my reports OK.
What is the reason Novell recommends these values and what could be the issue if I increase it?
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-Xmx -Xms and paging

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