[PJUG Javamail] Java Memory Management

[Douglas Bullard]

In our instance, the CPU was cranking at 100%, but no usable work was  
being done - 95% of the CPU's effort was doing GC.

JConsole is a godsend for figuring out what's going on  when this  
happens - if you haven't used it, it's a very, very helpful tool.

One of the things which helped us out of our spot was changing the GC  
parameters - tuning the GC is a bit of an art, and a bit of black  
magic.  Twiddle until it works.  I hear vague rumors that a self- 
tuning GC is in the works...


Doug


On Jan 1, 2008, at 14:03, Bill Kayser wrote:

> Blow up as in OutOfMemoryError thrown?  The JVM crashes?
>
> From: Chris Kessel/Lou Doherty [mailto:chriskessel at verizon.net]
> Sent: Tuesday, January 01, 2008 1:57 PM
> To: 'Bill Kayser'; 'Douglas Bullard'; 'Carlus Henry'
> Cc: 'Javamail'
> Subject: Re: [PJUG Javamail] Java Memory Management
>
> I was going to say, "Yea, it's easy", but that was a couple JVM  
> iterations ago.
>
> Basically, a main with a for loop that allocates an array of 1000  
> elements over and over and over. It'll blow up as the GC can't keep  
> up with it.
>
> From: javamail-bounces at pjug.org [mailto:javamail-bounces at pjug.org]  
> On Behalf Of Bill Kayser
> Sent: Tuesday, January 01, 2008 1:37 PM
> To: 'Douglas Bullard'; 'Carlus Henry'
> Cc: 'Javamail'
> Subject: Re: [PJUG Javamail] Java Memory Management
>
> That's a neat trick.  I'd love to hear the details on that.  Do you  
> mean that you ran out of memory before the GC could clean everything  
> up?  I'm pretty sure I could write a program that did nothing but  
> allocate memory (non rooted) and I can't imagine the JVM would fall  
> over.
> You can swamp the garbage collector by creating too many objects,  
> generating them faster than it can collect them - we've run into  
> that with Hibernate at work.
>
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