Memory space using a 32bit Java process on Redhat Linux

I have a java process that I need a lot of memory for. Its a 32 bit process, and I have no desire to have it as 64bit due to the huge pointers it forces.
So I know I can turn to Solaris where I will have close to 4GB of memory available for this process (right?). But are there Linux alternatives? I am especially curious regarding Redhat on intel64 machines as I have (which is the common desktop hardware nowadays).
I heard about the hugemem kernel for Redhat, but I am lost understading its nature. It is said it is not available for v.5 for x86. So is it available for the intel64 processors as I have? And what is the max memory space for a java process?
Any other bit of information about java 32bit process running on a linux flavor on an intel64 machine will be greatly appreciated.
thanks in advance!
Woody
Message was edited by:
Woody.Benoty

I'd say this is normal. There are a few things to consider when looking at an application like this:
1. The 14 MB your process consumes include the memory required to load the java virtual machine. That is, all the base classes, native links, the just in time compiler etc. 14 MB isn't a lot, all things considered.
2. When you display a message box, java will load additional classes and resources. They increase the heap size, though not really by 4 MB. Java preallocates portions of memory for the heap. If, for instance, your application consumes 16 MB of memory and you allocate another MB, the heap size may grow to 32 MB. Having a free section of heap space to spare increases performance, since java won't have to ask the underlying system for free memory every you create an object. You might want to check out your program in JVisualVM (deployed with every JDK6), which will tell you how much of the allocated heap size is really in use, or you can rely on the according methods in the Runtime class.
3. The JVM is capable of 'heap shrinking', meaning it will return allocated sections of memory to the OS once in a while. However, it will not do so unless the heap size is significantly larger than the used portion of the heap (otherwise, it would defeat the purpose of preallocating memory). So if you allocate 2GB of RAM when clicking your button and allow this memory to be cleared by the garbage collector, you'll observe that the heap will shrink again eventually.

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Management of memory space - using totalMemory() and maxMemory()

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RoyEpperson wrote:
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Dear All,
I was just writing to enquire whether there was a method of monitoring the size in memory of an external program being called via the Runtime.exec() method. I am trying to submit a program to a cluster and as I have no access to the source code of the program I am submitting I need some way of externally monitoring it's size and I was wondering whether this was possible in Java?
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Biologist wrote:
Dear All,
I was just writing to enquire whether there was a method of monitoring the size in memory of an external program being called via the Runtime.exec() method. I am trying to submit a program to a cluster and as I have no access to the source code of the program I am submitting I need some way of externally monitoring it's size and I was wondering whether this was possible in Java?
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Hi everyone!
I'm running a servlet Oracle iAS 9i, Jserv. It receives an image posted by a user and does a System.exec() which performs a call to convert (an image processing utility included in ImageMagick).
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java.lang.UNIXProcess.<init>(), line 54.
java.lang.Runtime.execInternal(), line -2.
java.lang.Runtime.exec(), line 553.
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Have you had any solutions to this pal?
I am also suffering. I tried closing the processes by:
Runtime runtime = Runtime.getRuntime();
Process proc = runtime.exec("/opt/sta_rpms.sh " + sFileName);
proc.waitFor();
proc.getInputStream().close();
proc.getOutputStream().close();
proc.getErrorStream().close();
proc.destroy();
proc = null;
but still after like a day...Though our codes are not alike, it sounds like the same reason.
Cheers!

How to check actual allocated and used memory for java process in solaris?

Hi,
I'm testing performance for java application on solaris 10. And I would like to know how to measure actual memory allocated and used for java process.
I'm setting -Xms512m -Xmx512m for my java process and I use prstat command to monitor it's memory. But I found that when I run prstat to check, in SIZE column is more than I setting (found 644).
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Thank you.

With Xms/Xmx you specify the Java heap size. On top of that comes the permanent generation (default max size 64m) and the C part of the process (the JVM itself with all its libraries and data).
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What's in the JVM Process's Memory Space?

Hello
I'm noticing the following behavior on an NT system. On
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Used Heap 5.5 MB
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After a "login" operation which loads a few more
classes:
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Used Heap 8.2 MB
java.exe memory (from NT Task Manager) 53 MB
Heap memory leaks have been ruthlessly suppressed
(thanks to OptimizeIt and careful programming). The
behavior I do not understand is that the NT process
(java.exe) increased in size by 17 MB when the Java
heap increased by only 3 MB. The .jar file in which the
application resides is less than 1 MB, so this 14 MB
growth can not be attributed to new classes being
loaded.
Does anyone know what is going into the process
memory space of java.exe? It tends to grow larger
and larger.
Should I even care? Do I want a large allocation of
process memory for java.exe, or will that hamper
performance of machines with less physical memory?
Posts on related topics in this forum have sometimes
advocated allocating a lot of memory to the JVM with
-X options.
Thanks

Hello
I am facing exactly the same problem on NT. However, on 2000 Server this problem doesn't seem to exist. Are you, by any chance, using JNI? We are extensively using JNI in our Servlets and found that there is definitely some momory leak there. We could not figure out any substantial leak at Java end. In NT's "Task Manager" java.exe is always listed first and very rarely the memory usage seems to come down. On 2000 Server the performance is far better.
Please visit this link:
http://forum.java.sun.com/thread.jsp?forum=33&thread=211330
Regards
Manish Bhatnagar

Locate rogue java process eating swap space.

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I'd start with ps -e -o vsz,pid,args | sort -nThe process with the largest VM footprint will be on the bottom.
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Spawn a java process using runtime.exec() method

Hi,
This is my first post in this forum. I have a small problem. I am trying to spawn a java process using Runtime.getRuntime().exec() method in Solaris. However, there is no result in this check the follwoing program.
/* Program Starts here */
import java.io.*;
public class Test {
public static void main(String args[]) {
String cmd[] = {"java", "-version"};
Runtime runtime = Runtime.getRuntime();
try{
Process proc = runtime.exec(cmd);
}catch(Exception ioException){
ioException.printStackTrace();
/* Program ends here */
There is neither any exception nor any result.
The result I am expecting is it should print the following:
java version "1.4.0"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.4.0-b92)
Java HotSpot(TM) Client VM (build 1.4.0-b92, mixed mode)
Please help me out in this regard
Thanks in advance
Chotu.

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Memory used by oracle 11g processes on solaris 10

I am running oracle 11.1.0.7 on solaris 10. The database uses some 280M virtual memory size for each oracle backup or user process. See the SZ column in output of ps -efl below.
I just wonder how come oracle that much of memory for each process. Is that something we can control through some system/database parameters or is that the way oracle 11g on solaris works?
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0 S oracle 2145 1 0 40 20 ? 284792 ? 12:18:11 ? 0:06 ora_dbw3_cttrain6
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user567271 wrote:
I am running oracle 11.1.0.7 on solaris 10. The database uses some 280M virtual memory size for each oracle backup or user process. See the SZ column in output of ps -efl below.
I just wonder how come oracle that much of memory for each process. Is that something we can control through some system/database parameters or is that the way oracle 11g on solaris works?As you have already said, it is "virtual" memory. This is not real, "physical" memory. Solaris has a virtual memory sub-system layer in it, as do almost all other modern operating systems. Google "operating system virtual memory" to find out more on what virtual memory is and how it works.
In terms of your question, virtual memory means that not all of a process's memory space needs to be in physical memory for it to run and execute. The process virtual memory space is broken up into equal sized pages, and only those pages currently being referenced (used) are mapped and read into physical memory pages. Thus the virtual size of a process is irrelevant to how much physical memory is being used. Look at the RSS column (ps -ely) for the physical memory used by each process - Resident Set Size.
Furthermore, an Oracle shadow server process (oracle) uses a large segment of shared memory for the SGA. This shared memory only exists once in physical memory, and is shared amongst all the shadow server processes. But it is mapped into the address space of each process, and so appears and is counted in the virtual and physical memory of each process.
So each reported virtual size (SZ) of each oracle process is also counting the mapped shared memory pages in each process, and so counting the same pages multiple times across all the oracle processes. You need to subtract the size of the SGA shared memory from the virtual size of each oracle process to determine the private, local memory per shadow process.
If you want a further breakdown of the memory map of each process, look at the manual pages for pmap (man pmap), which will break it down by text, private data, zero initialized, shared and other types. By subtracting the shared size from the resident size you can get a true view of the private, local memory per oracle shadow server process.
John

Can any java process exceed the maximum memory allocated

Hi,
I have a basic question on the memory settings. Assume I have a java process where the memory settings are like:
-Xmx1024m
where the server capacity is say 8GB Then can the process exceed the allocated memory of 1GB and go further say upto 4 GB.
If above thing is possible, how can we limit the process not to exceed the given limit? What settings need to be used.

Krish8 wrote:
Hi,
I have a basic question on the memory settings. Assume I have a java process where the memory settings are like:
-Xmx1024m
where the server capacity is say 8GB Then can the process exceed the allocated memory of 1GB and go further say upto 4 GB.
If above thing is possible, how can we limit the process not to exceed the given limit? What settings need to be used.Yes the used memory can exceed that if you e.g. are using memory mapped files. Don't know if you can restrict it unless your OS has some kind of support for it.
Kaj

Weblogic java process slowly hogging memory

My unix 'top' utility tells me that my Weblogic java process is slowly
hogging memory, over a period of hours under heavy load, until the machine
finally starts swapping and performance goes into the toilet.
I got a copy of jprobe, which I had hoped would show me that I have memory
leaks, but it said everything was fine, I could see the little graph of heap
memory getting sent back down to 10 Meg every minute or so. Then I bring up
'top' with no jprobe, and I watch "SIZE" grow to 250 Meg and I run out of
virtual memory. Anybody know what is up?
System info: Weblogic Server 5.1, sp5, Solaris 2.7, JDK 1.2.2_07.
Thanks in Advance
Greg

250M for WLS is not very much. How much physical memory is on
the machine? What do you have your heap size set to?
Use the command /usr/proc/bin/pmap to dump out the memory
segments of the JVM. You will find one of the segments labeled
'heap' this is not the Java Heap, this is the C heap. Does it
grow? If it does, do you have native code (type 2 db drivers)or
any other native code? The JVM also uses the C heap. Compiling
JSPs seems to use a lot of memory. JSPs compiled with SP9 will
use less C heap than pre-SP9.
There will be another 'anon' segement that corresponds to the
size of the max Java Heap as shown by the weblogic console.
The 'Total' should correspond to the 'size' you see in top.
Mike
"Greg Lems" <[email protected]> wrote:
My unix 'top' utility tells me that my Weblogic java process is slowly
hogging memory, over a period of hours under heavy load, until the machine
finally starts swapping and performance goes into the toilet.
I got a copy of jprobe, which I had hoped would show me that I have memory
leaks, but it said everything was fine, I could see the little graph
of heap
memory getting sent back down to 10 Meg every minute or so. Then I bring
up
'top' with no jprobe, and I watch "SIZE" grow to 250 Meg and I run
out of
virtual memory. Anybody know what is up?
System info: Weblogic Server 5.1, sp5, Solaris 2.7, JDK 1.2.2_07.
Thanks in Advance
Greg

OOM Killer is killing the Java processes without using the swap?

Hi All,
We are using RHEL 5 64 bit on blade server CISCO UCS B230-M2.
Below is the memory details on the server. I could see from the sar -r command it did not used the swap memory at all but it calls the OOM killer everyday.
su@ /root-> free -g
             total       used       free     shared    buffers     cached
Mem:           125        119          5          0          2         81
-/+ buffers/cache:         35         89
Swap:          251          0        251
The issue is occuring every day and doesnt allow any user to connect to the server in that perticular time, After some time we could see the below messages in /var/log/messages and once the java processes are getting killed it allow the new telnet connections.
Any help on this is much appreciated.
Oct 18 01:47:57 usdc01qd51 kernel: cpu 28 cold: high 62, batch 15 used:10
Oct 18 01:47:57 usdc01qd51 kernel: cpu 29 hot: high 186, batch 31 used:20
Oct 18 01:47:57 usdc01qd51 kernel: cpu 29 cold: high 62, batch 15 used:6
Oct 18 01:47:57 usdc01qd51 kernel: cpu 30 hot: high 186, batch 31 used:93
Oct 18 01:47:57 usdc01qd51 kernel: cpu 30 cold: high 62, batch 15 used:10
Oct 18 01:47:57 usdc01qd51 kernel: cpu 31 hot: high 186, batch 31 used:137
Oct 18 01:47:57 usdc01qd51 kernel: cpu 31 cold: high 62, batch 15 used:6
Oct 18 01:47:57 usdc01qd51 kernel: HighMem per-cpu: empty
Oct 18 01:47:57 usdc01qd51 kernel: Free pages:    37295696kB (0kB HighMem)
Oct 18 01:47:57 usdc01qd51 kernel: Active:15955130 inactive:6377121 dirty:1470607 writeback:0 unstable:0 free:9323924 slab:301569 mapped-file:1506506 mapped-anon:7952475 pagetables:78246
Oct 18 01:47:57 usdc01qd51 kernel: DMA free:0kB min:0kB low:0kB high:0kB active:0kB inactive:0kB present:9076kB pages_scanned:0 all_unreclaimable? yes
Oct 18 01:47:58 usdc01qd51 kernel: lowmem_reserve[]: 0 4024 126242 126242
Oct 18 01:47:58 usdc01qd51 kernel: DMA32 free:1202200kB min:1448kB low:1808kB high:2172kB active:275860kB inactive:55140kB present:4120800kB pages_scanned:0 all_unreclaimable? no
Oct 18 01:47:58 usdc01qd51 kernel: lowmem_reserve[]: 0 0 122217 122217
Oct 18 01:47:58 usdc01qd51 kernel: Normal free:36093496kB min:44024kB low:55028kB high:66036kB active:63544660kB inactive:25453344kB present:125151120kB pages_scanned:0 all_unreclaimable? no
Oct 18 01:47:58 usdc01qd51 kernel: lowmem_reserve[]: 0 0 0 0
Oct 18 01:47:58 usdc01qd51 kernel: HighMem free:0kB min:128kB low:128kB high:128kB active:0kB inactive:0kB present:0kB pages_scanned:0 all_unreclaimable? no
Oct 18 01:47:58 usdc01qd51 kernel: lowmem_reserve[]: 0 0 0 0
Oct 18 01:47:58 usdc01qd51 kernel: DMA: 0*4kB 0*8kB 0*16kB 0*32kB 0*64kB 0*128kB 0*256kB 0*512kB 0*1024kB 0*2048kB 0*4096kB = 0kB
Oct 18 01:47:58 usdc01qd51 kernel: DMA32: 21352*4kB 18549*8kB 13617*16kB 5772*32kB 1097*64kB 52*128kB 8*256kB 1*512kB 1*1024kB 1*2048kB 118*4096kB = 1202200kB
Oct 18 01:47:58 usdc01qd51 kernel: Normal: 144164*4kB 1746735*8kB 1130515*16kB 102420*32kB 1956*64kB 83*128kB 42*256kB 2*512kB 3*1024kB 1*2048kB 6*4096kB = 36093496kB
Oct 18 01:47:58 usdc01qd51 kernel: HighMem: empty
Oct 18 01:47:58 usdc01qd51 kernel: 14377659 pagecache pages
Oct 18 01:47:59 usdc01qd51 kernel: Swap cache: add 507, delete 507, find 163/244, race 0+0
Oct 18 01:47:59 usdc01qd51 kernel: Free swap = 263740076kB
Oct 18 01:47:59 usdc01qd51 kernel: Total swap = 263740648kB
Oct 18 01:47:59 usdc01qd51 kernel: Free swap:       263740076kB
Oct 18 01:47:59 usdc01qd51 kernel: 32770048 pages of RAM
Oct 18 01:47:59 usdc01qd51 kernel: 648871 reserved pages
Oct 18 01:47:59 usdc01qd51 kernel: 10183423 pages shared
Oct 18 01:47:59 usdc01qd51 kernel: 0 pages swap cached
Oct 18 01:47:59 usdc01qd51 kernel: Out of memory: Killed process 9529, UID 502, (java).
Thanks,
Sachin.

It looks like you experience low memory exhaustion. The kernel uses low memory to track allocations of all memory and the more memory you have, the more low memory will have to be allocated. When low memory is exhausted, it doesn't matter how much high memory is available, the oom-killer will begin killing processes to keep the server alive. There are a number of bug reports and patches available regarding this problem affecting Enterprise Linux kernels 4.4 - 4.8. Other solutions are to move to a 64-bit kernel or use 32-bit hugemem. Are you running NFS?
Perhaps you might want to try the following:
# cat /proc/sys/vm/lower_zone_protection
You can try to increase the value and see what happens:
# echo "250" > /proc/sys/vm/lower_zone_protection
To set this option on boot, add the following to /etc/sysctl.conf:
vm.lower_zone_protection = 250
As a last resort effort, you can disable the oom-killer. This option can cause the server to hang, so use it at your own risk.
Check status of oom-killer:
# cat /proc/sys/vm/oom-kill
Turn oom-killer off/on:
# echo "0" > /proc/sys/vm/oom-kill
# echo "1" > /proc/sys/vm/oom-kill

Learn about Java memory spaces?

Hi, I'm a student, and I need to do some research on and write a small paper about the "three or more Java memory spaces", what they do, how they differ.
The only problem is that spending a half hour searching google and reading quite a bit of documentation, I can't find any significant reference to or classification of these memory spaces! Can anyone provide me with a link to documentation that describes these memory spaces and their uses?
Thanks for your help!

Also
http://java.sun.com/products/hotspot/docs/whitepaper/Java_HotSpot_WP_Final_4_30_01.html
http://java.sun.com/developer/technicalArticles/Programming/turbo/ and the documents referenced at the end of the article
http://java.sun.com/docs/hotspot/gc1.4.2/faq.html
http://java.sun.com/docs/hotspot/gc5.0/gc_tuning_5.html
Thes will lead you to additional documentation.

Is there a method I can use to test the space cost of a Java program?

I am trying to test the space cost of a Java program (or a few lines of executed codes), however...
Firstly I tried to use the method freeMemory() in runtime class at start and end of a number of lines tested on, and then find the differences between them. But because I don't know when JVM releases memories, this idea seems not working.
I also tries to use the -verbose:gc to print the GC actions, which is also hard to be automatically collected (Computing the results one by one by hand is too burdensome).
Is there a method in some classes can be used for doing this? Could anyone help me on this, please?

Up _+ ...

Memory space using a 32bit Java process on Redhat Linux

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