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From Reynir Þór Hübner <rey...@hugsmidjan.is>
Subject Re: JVM memory size changing dramatically
Date Wed, 28 Jul 2004 16:25:42 GMT
Hi,
The only good way of knowing what your setup is capable of, is testing.
if you do not reach the 500 concurrent visitors mark in simulation 
testings (using JMeter or some ohter stress tool) you will probably not 
be able to serve 500 real concurrent users.

Be sure to run the test over night, or at least for more than 5 or 10 
minutes, as your application might be leaking some memory over time.

Regarding the strange memory behaviour shown in TaskManager, when it 
goes up and then down, taskmanager is not showing correct information 
all the time. Try running tomcat in a command promt window, then watch 
how taskmanager reports memory statistics when you minimize the window.

if memory goes steadilly up, you should check if you are reloading jsp 
pages, or using developement settings for the jsp sservlet. Behaviour 
like you described could happen if you have context-reloading set to 
true, then if something changes in either web.xml or WEB-INF/lib or 
/WEB-INF/classes directory the classloader for that context is reloaded. 
  This can take up some memory, that usually is returned in GC.
hope it helps
-reynir


Safadi, Mazin wrote:

> 
> 
> But windows has enough space, 2GB memory, Dual processors, this app. is
> running but still Tomcat does not receive hits, what will happen if the
> server has up to 500 visitors concurrently, 
> How windows will handle this?
> How to make sure that JVM will not goes down?
> 
> 
> 
> 
> 
> 
>  
> 
> 
> 
> -----Original Message-----
> From: Shapira, Yoav [mailto:Yoav.Shapira@mpi.com] 
> Sent: Wednesday, July 28, 2004 17:19
> To: Tomcat Users List; msafadi@massar.com
> Subject: RE: JVM memory size changing dramatically
> 
> Hi,
> Windows needs additional space for other things (including possibly idle
> thread cleanup) and swaps your process into a paging area temporarily.
> It's fairly standard practice, and as you noted results in no errors, so
> don't worry about it.
> 
> Yoav Shapira
> Millennium Research Informatics
> 
> 
> 
>>-----Original Message-----
>>From: Futchi [mailto:msafadi@massar.com]
>>Sent: Wednesday, July 28, 2004 12:11 PM
>>To: Tomcat Users List
>>Subject: JVM memory size changing dramatically
>>
>>Hi all,
>>           I am running tomcat 5 on Win2003 server, my single app. has
>>several threads running in the background (threads loading and writing
>>data, detecting URL connections).
>>
>>Tomcat starting-up with 80 up 90 MB memory size as Win2003 shows in the
>>Tasks Manager, it keeps running stable and getting up and down between
>>80 and 93 MB memory size. After several hours, memory size gets down to
>>5 MB very fast, and then start goes up to 90 MB also fast.   This
> 
> change
> 
>>happening in about 2-3 minutes only, then it becomes stable again
>>jumping between 80-93 MB memory size.
>>
>>While this happening Tomcat is up and running, also my App. is up and
>>running. I do not have any memory error messages.
>>
>>
>>I doubt it is the GC, Anybody can explain that?!!!
>>
>>
>>My JAVA_OPTS as follows
>>
>>
>>JAVA_OPTS=-server -Xms256m -Xmx768m -XX:NewSize=64m -XX:MaxNewSize=64m
>>-XX:SurvivorRatio=8 -XX:MaxTenuringThreshold=5
>>-XX:TargetSurvivorRatio=75 -XX:PermSize=32m -XX:MaxPermSize=32m
> 
> -Xss128k
> 
>>-XX:+DisableExplicitGC
>>
>>
> 
> 
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