Hello Anurag
What is the version of your Portal system ?
In the SAP NetWeaver 'Java' systems, you don't have 'Dialog response time' as it is in ABAP systems as there are no Dialog work processes but J2EE server processes.
As mentioned, if you have a Portal from 7.1 version, go to http://<host>:<port>/nwa -> Availability and Performance -> System Overview.
You can see there the Host CPU usage and response times between the Portal components
If you want the details per Portal requests / transactions, go to Availability and Performance -> Resource Monitoring -> System performance statistics (Assuming your Portal is from 7.1 version).
Then if you have Wily Introscope installed, you can find the metrics you are looking for in the Wily Console -> Portal Triage Dashboard -> Host CPU usage / Portal Request Response Time
Best regards,
Johann