Suricata

Suricata insert DPDK module, DPDK responsible for package and release the package. when I test ,I found the problem:first,send a lot of different IP packets,the flow application memory reach the flow.memcap, the process of IPS takes up resources achieve a relatively stable value.then send less fixed IP packets, the flow application memory decreases, but the process of IPS takes up resources have not fallen.last, send a lot of other different IP packets,the process of IPS takes up resources increase a little,then send less fixed IP packets, the flow application memory decreases, but the process of IPS takes up resources still have not fallen.the process of IPS takes up resources will become more and more big.
so ,which module should I check,what should I do,thank you.