Memory Usage

I am using Persistent Task Queue for the background worker class. When
the backgroundrb server is started it consumes as much
as a Rails instance consumes. Consider it consumes 300MB memory at the
beginning, but gradually it goes upto 600MB.
I am not getting why this worker class is consuming this huge memory.
The thread pool size is 5. In the same worker class
i am making a call for the add_periodic_timer twice for the two
different methods.

Can anyone figure out what might be causing it?