Logstash consume a large amount of memory and CPU

Hello,

We are making some implementation on our system of logstash in order to retrieve some information on differentes sources (BDD,FILE, JMX).
We implemented 3 windows service that use the same logstash context with 3 different configuration (on input source for each kind of data to retrieve).

It's appear that theses 3 service consume a lot of CPU (20% each) withou any reason (no activity on the log during my check). I also not seen any relevant informations in log.

How could I control and validate what's not working as expected ?

Logstash Version (1.5.4)