high load CPU for a CHR working QT

A simple configuration which was made in the CHR, we put it to manage the bandwidth.
CHR connected to a group of NASs (all are Mikrotik), they acts as a pppoe server on our network, 2000 active subscribers.
Queue Tree (PCQ) configured as the image 1 :
image1.PNG
and below is the diagram:
Diag-netw.png
thank you