Thanks, Chris. I'll do some load testing. I was thinking of using siege or
apache bench. _Tomcat: The Definitive Guide_ is my guide.
Do you know of a better way of getting heap numbers out of Java? Right now
I've got three metrics: jvm_mem_free; jvm_mem_max; jvm_mem_total. Examining
the graphs, I see that 'free' and 'total' are not exact opposites. 'max'
doesn't change and I believe this is set with the option -Xmx2048m. These are
the java options relating to the heap:
-Xmx2048m
-Xms1024m
-XX:MaxPermSize=256m
-XX:+UseParallelGC __/
__/
Jvm_mem_total creeps up to the max over time (about 2 days): __/ During that
time, jvm_mem_free fluctuates regularly, like this: /\/\/\/\/\
-----Original Message-----
From: Christopher Schultz [mailto:[EMAIL PROTECTED]
Sent: Thursday, March 06, 2008 11:54 AM
To: Tomcat Users List
Subject: Re: Tomcat Status Metrics: RRDTool Graph: Analysis
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David,
David Smithson wrote:
| Hi, Christopher. Thanks for your reply. This is a typical hour on
| any given day. What other things should I be looking at in Tomcat
| and Java? I've got plenty of metrics from other parts of the
| operating system.
Typically, I look at heap activity (in Java, not just free memory from
the OS's perspective) and CPU utilization. The cleaner your heap, the
faster everything will run.
| I've got my on the JVM memory metrics that come from the Tomcat
| status page as well. If I'm not mistaken, these numbers represent
| JVM memory fluctuations and relate to garbage collection routines.
Probably. Look for heap activity that looks like this: /\/\/\/\/\/\
~ __/
~ ___/
~ ___/
When you start seeing this: __/
You have a problem!
Just because your threads are not being used too much doesn't mean there
aren't other problems lurking. Even with low thread utilization, a bad
heap graph can mean that you're just waiting around for an OOME.
Consider performing load tests and watching the numbers instead of just
watching a typical hour of a typical day. You need to plan for peak
load, not for average load.
- -chris
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