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Subject: RE: Load testing, benchmarking, and tuning
Date: Tue, 7 Aug 2007 13:43:39 +0100
Message-ID: <DDBBD1E00935D144AB9563D57EF98D624EF482@raccoon.melandra.net>
Thread-Topic: Load testing, benchmarking, and tuning
Thread-Index: AcfY7hfnFtW/KCuFRCKcLgVBuvU6bAAASyKw
References: <12032715.post@talk.nabble.com>
 <DDBBD1E00935D144AB9563D57EF98D624EF481@raccoon.melandra.net>
 <12033169.post@talk.nabble.com>
From: "Peter Crowther" <Peter.Crowther@melandra.com>
To: "Tomcat Users List" <users@tomcat.apache.org>

> From: rhull [mailto:rhull@pobox.com]=20
> I can't find any reason to believe I am.  I'm running on a 1.5mb
> download/256mb upload cable connection.  The Linux box is on=20
> similar.  The
> requests are fairly short HTTP POST request (couple hundred=20
> bytes), and the
> responses from the servlet are under 10K each.

OK, you're bottlenecked there I think (assuming you mean 256 *k*b rather
than 256 *m*b upload).  Consider: 10 kbytes is around 100 kbits (include
framing and other overheads).  15 transactions per second is therefore
15 x 100 =3D 1,500 kbits =3D pretty close to 1.5 Mbit/s.  I suspect that
isn't a coincidence.

> Right now, the servlet is serving the contents of ~1500 small=20
> xml files (the
> next phase of the project moves the files to memory in a service to be
> served up to the servlets).  My suspicion was that a lot of=20
> the system time was due to file activity/swapping.

Sounds likely.  Tracing system calls would tell you.

That's a pretty meaty system, doing some pretty small things.  600tps is
600/8 =3D 75tps per core; you've plenty of memory to go at, there's no
hardware network to drive, and the file contents will be in the OS disk
cache fairly early on in the test.  I can believe the numbers you're
getting with that webapp, and I suspect they'll go *up* if you bring the
files into memory.  At the moment, it wouldn't totally surprise me if
most of your app fitted into the L2 cache on the CPUs.

		- Peter

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