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From Christopher Schultz <>
Subject Re: Hundreds of Instances
Date Tue, 04 Dec 2007 16:13:48 GMT
Hash: SHA1


Breno Jacinto wrote:
> Hi Christopher,
>>>     Not really. I dont have the exact numbers, but I think we'd get at
>>> most 50 users every 10 minutes = 5 users / min. I believe that´s
>>> pretty low.
>> Is that estimated, or measured?
>     It's just estimation. BTW, is there any tool that could help me
> with effectively measuring this, get some statistics etc?

You could turn on the AccessLogValve and then simply look at the log
files. Another option would be to write your own Valve or Filter and
record the accesses yourself, but the AccessLogValve is already there. I
think it can easily be configured to emit "standard" httpd-style logs so
you can use tools webalizer to graph the usage over time and stuff.

> JAVA_OPTS="-server -Xms128m -Xmx384m
> -Djava.library.path=/usr/src/dbxml-2.2.13/install/lib/"

Really? From your other message, you make it look like Java is taking
something like 1GB of memory. Sure, the JVM adds some overhead to the
heap size you configured, but it shouldn't be more than 5% or 10%...
nothing like 200%.

>     OK. The only problem is that this site is on production, but I
> believe it'll possible to run Tomcat under the profiler and get some
> significant results. An alternative is to replicate the system and try
> simulating some load and common operations (which I found out JMeter
> is the tool for this).

If you really are only serving 10 users per minute, attaching a memory
profiler isn't going to significantly impact your performance (unless
you're running with an old VM which requires disabling the JIT in order
to instrument the VM). You said you're running 1.5.0, which should allow
this type of instrumentation.

> :)). I had this experience once - it's hard to believe char[] are
> so evil! :).

Not evil... just plentiful. All those class and method names gotta go

- -chris

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