[rules-users] Drools slowness in first calls

[Mark Proctor]

On 5 Jun 2014, at 16:48, Gael <gael.weil-jourdan at prestataire.april.com> wrote:

> Hi, 
> 
> We are using Drools for a heavy process and we notice some slowness during
> the first calls to kbases (containing about 1500 rules each) using
> StatefulKnowledgeSession. 
> Even if the kbase is "loaded", we need to make some "fictive" calls (fire
> the rules with some facts) until it begins to respond within a reasonable
> time. It's like we need to warm it up.. 
That’s sort of how the JVM works, it takes many thousands of iterations for JIT byte code to kick in. There is also some additional byte code generation we do on the fly to speed things up - you may also be seeing this.
> 
> Any idea about what Drools does during this time? 
> Is there a way to programmatically launch these processing without the need
> to have facts ? 
Not really, this is how the JVM works, likewise the additional byte code generation we do.

In 6.x there is an additional one off cost too, in calculating all the node memories and segments. This also is done “on the fly”, during the first session.

Mark
> 
> Thanks in advance and sorry for my english. 
> 
> NB : we use Drools 5.5. 
> 
> Regards, 
> Gael
> 
> 
> 
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