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From Peter Crowther <>
Subject RE: Optimal number of Tomcat instances versus Number of cores
Date Wed, 14 May 2008 11:46:32 GMT
> From: HLL []
> I have a doubt. How can I determine the optimal number of
> Tomcat servers in
> the same machine to achive the best throughput depending on
> the number of
> cores of the machine? That is, which is the optimal relation
> between number of tomcats and number of cores.

Measure your application, under your expected load, on your hardware.  There is no other way.

If your application is well optimised and is not waiting on locks, the optimal number of Tomcats
may be 1.  This optimises the cache behaviour of the cores, as you don't have multiple copies
of the same code and data loaded at different locations and competing for cache lines.  Lock
contention, garbage collector behaviour or many other variables could change that, and make
it more optimal to segment your application.  If your machine is large enough to have a memory
architecture where some processors have faster access to some memory, the optimal number of
Tomcats may be one per memory segment - but this will need a *lot* of analysis and tuning.

[For future posts to forums: A better English translation may be "question" rather than "doubt"]

                - Peter

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