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:[EMAIL PROTECTED] Sent: Wednesday, July 28, 2004 17:19
To: Tomcat Users List; [EMAIL PROTECTED]
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:[EMAIL PROTECTED] 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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