use of memory by java on hpux

[Shivkumar]

Dear Sirs,

In what respect java uses memory (ram) different than other software such as c, c++ etc ?

Thanks,
Shiv

[Bill Hassell]

Java code doesn't use memory differently, but unlike most simple c++ programs, a lot of the library code is threaded so many subprocesses (threads) may be started. Java seems to use a lot of additional memmory, but this is generally due to Java libraries and choices made by programmers.

[Arunvijai_4]

Shiv, JVM uses lot of memory in any OS, you can try loading a applet in your IE and check task manager :-(. Since Java built on top of C and C++, it consumes more memory and CPU.

-Arun

[Arunvijai_4]

http://www.javaworld.com/javaworld/jw-02-1998/jw-02-jperf_p.html

[ Performance tests show Java as fast as C++]

-Arun

[Joseph Loo]

hi shiv,

i like this explanation:

http://javaboutique.internet.com/articles/java_memory/

regards.

[Yogeeraj_1]

hi shiv,

please allow me to add the following informations that will allow you to monitor your "java"

if you have glance plus, you can run the following:
glance -j10 -adviser_only -iterations 2 -syntax ./gln_proc_template_syntax_file


which will give you a detailed output which will look as:
# User CPU Util Cum Disk Thd
#Process Name PID PPID Pri Name ( 200% max) CPU IO Rate RSS Cnt
#------------ ------ ------ --- -------- ------------ -------- --------- ------- ---
# 10/24/05 10:27:57 C= 80 D= 9 M=100 S= 55
java 2143 1 255 root 0.0/ 0.0 394.4 0.0/ 0.0 141.3mb 10
# 10/24/05 10:28:07 C= 88 D= 10 M=100 S= 55
java 2143 1 255 root 0.0/ 0.0 394.4 0.0/ 0.0 141.3mb 10



hope this helps too!

kind regads
yogeeraj

[Vibhor Kumar Agarwal]

Java requires a bit more memory than C/C++ as its interpreted and others are compiled.

So it caches some in Ram to increase the performance. Otherwise it will become quite slow.

[Shivkumar]

Yogeeraj, When i executed your command i got the below error message:

Syntax file ./gln_proc_template_syntax_file is not available. Use default syntax file.

[Shivkumar]

Someone told me that java uses only heap and not stack area of memory ??

[RAC_1]

You can control the java memeory usage to certain extent. When starting java, you can specify the initial heap size, maximumum heap size.

Check what your process is using.

ps -efx|grep [j]ava

java -help will give available options.

[Yogeeraj_1]

hi again,

sorry, you will also need the template file.

see attachment.

kind regards
yogeeraj

[Yogeeraj_1 · Accepted solution]

hi again,

sorry, you will also need the template file.

see attachment.

kind regards
yogeeraj

[C. Beerse_1]

From my coding point of view, with c one can write code with the least memory usage.

C++ is a superset of c, however, there are way more functions in more libraries which use more space. Then C++ has some 4-gl and/or object-oriented features, including memory managers and garbage collectors and such. In the end, both c and C++ provide binaries that do need some libraries but that's it. The major difference will be a larger text-size for C++.

Then Java is more a 4-gl and/or object-oriented than C++, relying more on the memory management and the garbage-collector. This might result in a smaller text-size but will give a larger data-size And at run-time, java does need its virtual machine, which does occupy its resources.

So from code point of view, I see c as the most lean and clean code and java the most wastefull. However, with larger code sets, the differences will become less.

If you are willing to know, try to find something that is created in java and c/c++. Like 'hello_world.c' (just print the string "hello world" on the screen). I do know vnc (http://www.realvnc.com), that provides binary viewers for lots of platforms and also a java viewer.

[Ted Buis]

I don't believe that Java will be as fast as C or C++ in general. Data I have seen has it narrowing the gap, but I would think that a well optimized C or C++ compiler would beat Java almost always.

Memory reuse is different in Java where there is garbage collection, versus expicit control of this in C or C++. There are many debates over the merits of each approach. Well written C or C++ is likely to be better, but that assumes the code is well written.

[Ted Buis]

For more on Java GC then go to:
http://www.hp.com/products1/unix/java/java2/hpjtune/index.html