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From Rizwan Merchant <rizwan.merch...@sysconet.ca>
Subject Re: tomcat memory usage questions
Date Tue, 03 Oct 2006 14:30:19 GMT

Thanks for the response Robert.
Is it abnormal to see the mem usage % for tomcat to go as high as 80 or 
90%? Currently its only at 11%, but I am wondering at what point I 
should start panicking. :)

Robert Harper wrote:
> The memory should peak at some point and the go up and down with need. There
> are a few things you have to be aware of though. The garbage collector is a
> very low priority thread so if your server never has a dull moment, you end
> up exhausting memory just because the garbage collector does not get a
> chance to run.
>
> Care in development should be taken with respect to use of objects and
> having circular references. You can cause memory leaks with circular
> references because you might leave free and object from the servlet but then
> have two objects referring to each other and the GC will not see them as
> having gone out of scope. Another thing to think about is if you are doing a
> lot of string concatenation the StringBuffer object is much better to use
> than the String object. StringBuffer will be easier on memory and more
> efficient.
>
>
>
> Robert S. Harper
> Information Access Technology, Inc.
>
> -----Original Message-----
> From: Rizwan Merchant [mailto:rizwan.merchant@sysconet.ca] 
> Sent: Tuesday, October 03, 2006 7:41 AM
> To: tomcat
> Subject: tomcat memory usage questions
>
> Hi,
> We recently developed and deployed a web based application using the 
> following technologies...
>
> Struts
> Spring
> Hibernate 3.0
> Mysql 5.0
> tomcat 5.5
> Linux Fedora Core 4
>
> After the system went live, I have been monitoring the CPU and memory 
> usages. I dread the outOfMemory errors and am a little paranoid about it.
>
> There are 2 main processes I am monitoring, tomcat and mysqld.
> The tomcat process memory usage is slowly creeping up...after 8 hours of 
> application usage it is at 13.3% and the mysqld memory usage is at 1.3%.
>
> I am wondering what kind of pattern I should be observing for the memory 
> usages. Should it go up and then down again (like the CPU usage)? Or is 
> it ok for it to slowly go up (the way it is doing right now)? The swap 
> memory is not being used, so I am guessing thats a good thing.
>
> Also, someone told me that hibernate and spring will try and cache 
> everything it can, which could be the cause of the memory creeping up 
> slowly. Is this true? and if it is, will this be a problem when the 
> memory gets to a high number like 80 or 90% ?
>
> Also, is there a way to tell if there are any processes spawned by 
> tomcat that are hanging around uselessly?
>
> Any help, ideas, tips would be appreciated. I am just concerned about 
> having any memory issues with this LIVE application.
>
> Thanks,
> -Riz.
>
> <http://forum.springframework.org/newreply.php?do=newreply&p=79473>
>
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