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From "Peter Crowther" <>
Subject RE: Load testing, benchmarking, and tuning
Date Tue, 07 Aug 2007 11:59:31 GMT
> From: rhull [] 
> Load testing with WAPT from a Windows box across the internet 
> to Tomcat
> running on the Linux machine, I'm only seeing something around 15
> transactions per second.  This seems like an unlikely low 
> number to me.

Are you bottlenecked on your internet bandwidth?  Are you bottlenecked
on latency, if you're not re-using HTTP connections?

> When I run load testing local to the Linux box using Siege, I'm seeing
> around 600 transactions per second.  This seems like an 
> unrealistically
> large number to me, and I assume the TCP/IP loopback is 
> taking a lot of
> network-related effort out of the equation.

Why do you feel this is unrealistically large?

Loopback will take a lot of the hardware and driver issues out, yes.
Can you not set up a second Linux box that shares the same LAN and test
on that?

> 29503 tomcat    25   0 1356m 200m  13m S  711  2.5  41:05.61 java

8 core box?  Looks like it.

> There's obviously some load on the box (though not 
> necessarily CPU), but it
> certainly doesn't seem to be maxed out close to 100% of any resources.

At under 10% free CPU, I'd call that "close" to maxing out the CPUs.
71% system time is certainly interesting - are you being clobbered by
context switches between Siege and Tomcat?  A swift "vmstat 5" will tell
you.  Look in the "cs" column.

> So, I'm kind of stuck:
> A) How can I determine what kind of ballpark, realistic transaction
> throughput I *should* be expecting with my particular combination of
> hardware and software?

As you are, except I'd separate Siege onto its own box.

> B) How can I determine what the bottlenecking factor(s) is(are) on the
> throughput?

Same as always - Java's no different, with the possible addition of
locking issues in some webapps and having to set Tomcat's heap sizes.
If you're used to load testing other apps, you won't see many surprises
with Tomcat.

		- Peter

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