RE: How can Java eat up 160meg of memory?

Jeffrey --
 Your comment about "built-in cleanup" may not be too far off the mark.
 At COMMON Last Spring there was a presentation about "small object
performance" on the AS/400. It turns out that the string functions in Java
create a LOT of small objects that get discarded. The "garbage collector"
has to clean up this mess, creating a performance problem.

 The example cited was an application that absolutely fit Java's string
handling capability. (It was something like parsing cash register
information or some such thing). The problem was the application ate a
good-sized model AS/400 model 170 alive. You guessed it -- running the
garbage collector!
 The presenter was from Rochester and had been assigned to figure out what
was happening in this application. His report back was:
*       The application did in fact make proper use of the JAVA string
functions.
*       The way string functions are defined in Java will result in the a
LOT of "garbage" to clean up.
*       The problem was a fundamental language definition problem.
*       The recommended change was to re-code using either JAVA stringbuffer
data types (which do not have the built-in sub-string functions etc -- but
also do not create nearly the garbage to clean up). -- OR -- use the JAVA
code as a prototype and re-code in another language(!).
The main point of the presentation:
*       The Java language has pieces of it's definition that _will_ cause
problems on _ALL_ platforms. Yes they tried the application in the report on
other platforms -- some IBM some "others". (Would you believe the AS/400
garbage collector was the fastest of the bunch ;-) ?) 
*       JAVA is no programming panacea. Just another tool to be used
appropriately. (OK OK -- no flames for suggesting that the marketing hype
should be ignored from time to time).

George Lemen
Sr. Project Analyst
CIBER Inc
Weyerhaeuser CER Technical Support and Operations Manager
Weyerhaeuser phone: (253) 924-7975
Weyerhaeuser e-mail: george.lemen@weyerhaeuser.com
CIBER Phone (425) 451-2575 x142
CIBER E-mail: glemen@ciber.com

> ----------
> From:         Jeffrey L. Morris[SMTP:jlm@dessertfirst.com]
> Reply To:     MIDRANGE-L@midrange.com
> Sent:         Monday, February 28, 2000 12:57 PM
> To:   MIDRANGE-L@midrange.com
> Subject:      Re: How can Java eat up 160meg of memory?
> 
> >We have an application running on an NT server.  It's a pentium pro 200
> with
> >160meg of memory and 2 2gig scsi hard drives.
> >
> >Now, this application is "written in Java!!!".  First of all, as
> expected,
> >it's a slow running app.  but I can deal with that.
> >
> >The real problem is after only 5 days of running, we have to reboot
> because
> >we get so many "out of memory" errors.  this is a machine that needs to
> be
> >24/7.
> >
> >I can only assume it's the "awesome" builtin cleanup with Java that is
> >eating resources like candy.  I run my pentium 200mhz PC with 48meg of
> >memory for up to 3 weeks at a time and never get memory errors (it just
> >reboots itself..haha..).
> >
> >So, maybe Java cleanup isnt so good?  Maybe there is some knowledge of
> >memory management needed that this application doesn't use?
> >
> >I'd be interested in hearing what folks have to say.  I'm not saying what
> >the software is, though.  Maybe if you ask privately I'll tell.  ;)  This
> is
> >more of a Java gripe than a software gripe, but they do go hand in hand.
> >Maybe "written in Java" means to steer clear?  160meg of memory is a LOT
> of
> >memory to eat up in a few days.
> >
> 
> Maybe you should try running it on a machine that has a Real Java VM,
> instead of MicroSoft's bolluxed-up version?  (My opinion.., see Sun's
> lawsuit against MS for further details..)
> 
> JLM
> 
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