I'm sorry: cpu usage is not 100% because Java:
53% java, 47% Apache Server...
Actual report:
86000 loops, 7128K ram + 5072K virt, rt.free()=2097144
Edson Richter
----------
From: Michael E. Moores
Sent: quarta-feira, 5 de janeiro de 2000 17:40
To: Edson Carlos Ericksson Richter
Cc: [EMAIL PROTECTED]
Subject: RE: heap space and performance
so you can also see the heap get used up
with the win32 JDK?
i don't see how the blackdown JDK can be used
for programs that persist for long periods.
i tried several versions of that code.
i agree you will always get a performance
benefit by NOT calling object contructors inside of a long running loop.
but my reason for doing it is to test out the
jvm garbage collection and determine if the JDK is
usable in a real application.
i think the jvm/jdk has a big leak with one or more of the
classes used. i was having the same problem with HttpServlet..
i cannot build a website with servlets and have it run
longer than about 40,000 requests; using a servlet
that DOES NOTHING BUT PRINT HELLO!
i placed the main code in work() to make it obvious that
the objects fall out of scope.
here is the latest version, with construction IN THE LOOP!
it runs out of heap after about 45,000 iterations,
on linux 2.2, blackdown 1.2 (glibc 1.2.1)
????who can show me this running a million iterations?????
public class newtest extends Thread {
URLConnection yc;
Runtime rt = Runtime.getRuntime();
String inputLine;
int thflag;
public static void main(String[] args) throws Exception {
new newtest( args );
}
public newtest( String [] args ) {
int arg;
thflag = 0;
arg = Integer.parseInt( args[ 0 ] );
this.start( );
for( int i = 0; i < arg; i ++ ) {
work( i );
}
thflag = 1;
}
private void work( int i ) {
try {
if( i % 100 == 0 ) {
System.out.println( i + ": " + rt.totalMemory( ) + " bytes\n" );
}
URL yahoo = new URL( "http://127.0.0.1/" );
yc = yahoo.openConnection( );
BufferedReader in = new BufferedReader(new
InputStreamReader(yc.getInputStream()));
while((inputLine = in.readLine()) != null) {
//System.out.println(inputLine);
}
in.close();
in = null;
yahoo = null;
} catch( IOException e ){ System.out.println("IO EXC\n"); thflag = 0;}
}
public void run( ) {
while(thflag == 0 ) {
try {
this.sleep( 5000 ); // Encourage Garbage Colection every 5
seconds
rt.gc( );
} catch( Exception e ) {}
}
}
}
At 05:16 PM 1/5/00 -0200, you wrote:
>Well, I've read your considerations, and make sense.
>
>But, I've tested this at work: using jdk1.2.2 final from Sun for NT (is at
>my hands here).
>And memory consumption does goes up with the code that I've writed...
>
>I'll try the code in a Linux box at this night, and make new
>considerations. Really, using new() you will make an new allocation too.
>Reading my old notes I've noted that using a class scope variable the code
>run fastest (I've get this tip from Sun Dev. Conn.).
>
>Something that you can do to "inform" to Garbage Coll that a variable is
>no more in use is putting Null value in the variable after their use.
>
>Try this, and report-me if you have success.
>
>No problems in contact-me directly.
>
>About e-commerce, values, and so on, I'm developing a healt care app, and
>I know what about it. But Java (especially JSP and Servlets) is more
>stable (I can't guarantee Linux version) than Visual Basic (by example)
>and anyone take less errors coding in Java than C.
>
>[]s
>
>Edson Richter
>
>
>----------
>From: Michael E. Moores
>Sent: quarta-feira, 5 de janeiro de 2000 16:55
>To: [EMAIL PROTECTED]
>Subject: RE: heap space and performance
>
>(edson, i should have CCd you..)
>
>
>Edson (& java-linx),
>
>this code below runs out of heap space even faster than
>my original program. sorry the code probably does not
>look good after being pasted into this email..
>but the basic -->test<-- is to write some code which
>will 1) actually do something and 2) will run -->FOREVER<--
>(well... 6 months would be acceptable)
>
>i want to know that i can use the blackdown implementation
>for serving a medium volume ecommerce site which is responsible
>for millions of dollars of revenue.
>so far, not so good. but i am not a senior java developer,
>so some inputs would be very much appreciated!
>
>i can bascially make any code run out of heap (latest build of 1.2)
>even if i use this in a loop and then fall out of scope:
>Integer[] int_a = new Integer[100000];
>
>in the code, you took a reference declaration and moved it
>into class scope. i don't see how this does anything.
>we are still calling new() in each iteration, and the garbage
>collector SHOULD eventually free up the space.
>the 5 second thread does not do anything more than making gc run a bit more
>often; memory just goes up and after 40000 iterations blackdown jdk
>dies hard.
>moving declarations into class scope is not a rule we should use
>unless that variable is shared amongst many methods and/or
>must persist across method calls.
>why does it matter if i repeat the use of new()?????????
>i am not allocating the whole heap before the gc runs!!!!!!!!!
>
>
>Edson wrote:
> >Heap consumption and performance are real problems in Java.
> >But some great pratices in coding solve (or amenizes) the problem:
> >
> >1) Don't repeat declaration of common used variables:
> >
> >2) Create a thread in your main class taking a "forced garbage collection".
> >
> >See the following program, that I've reorganized to avoid duplicated
>declarations, and should work forever:
>
>import java.io.*;
>import java.net.*;
>
>public class newtest extends Thread {
> URL yahoo;
> URLConnection yc;
> Runtime rt = Runtime.getRuntime();
> BufferedReader in;
> String inputLine;
> int thflag;
> public static void main(String[] args) throws Exception {
> new newtest( args );
> }
>
> public newtest( String [] args ) {
> int arg;
> thflag = 0;
>
> arg = Integer.parseInt( args[ 0 ] );
> this.start( );
>
> for( int i = 0; i < arg; i ++ ) {
> work( i );
> }
> thflag = 1;
> }
>
> private void work( int i ) {
> try {
> if( i % 100 == 0 ) {
> System.out.println( i + ": " + rt.totalMemory( ) + "
> bytes\n" );
> }
>
> // the declarations was transferred to class
> scope, avoiding wasted
>memory allocation
> yahoo = new URL( "http://127.0.0.1/" );
> yc = yahoo.openConnection( );
> in = new BufferedReader( new InputStreamReader(
> yc.getInputStream( ) ) );
>
> while( ( inputLine = in.readLine( ) ) != null ) {
> //System.out.println(inputLine); don't
> care about the output..
> }
>
> in.close( );
> } catch( IOException e ){
> }
> }
>
> public void run( ) {
> while(thflag == 0 ) {
> try {
> this.sleep( 5000 ); // Make a forced
> Garbage Colection every 5 seconds
> rt.gc( );
> } catch( Exception e ) {
> }
> }
> }
>}
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