Broker Publish performance slow

Based on the dynatrace monitoring, we noticed that the IS publish process causing some delay. worst will go up to 8 sec per publish. we are using the guaranteed document type and perform publish heavily for txn logging purposes.

this happen intermittently and below is my broker configuration :

is the disk IO causing the problem? based on my own read up, looks like broker disk IO is OK.

what will be the possible caused?

Can you Please check Jvm usage and threads consumed by trigger and Is jvm usage ,it will be the cause of slowness