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From "Peter Crowther" <Peter.Crowt...@melandra.com>
Subject RE: Load testing, benchmarking, and tuning
Date Tue, 07 Aug 2007 12:43:39 GMT
> From: rhull [mailto:rhull@pobox.com] 
> 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 
> similar.  The
> requests are fairly short HTTP POST request (couple hundred 
> 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 = 1,500 kbits = 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 
> 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 
> 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 = 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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