Can anyone suggest me....
wxites It depends on the programming language. There are profilers for almost every language. Search and set up the right profilers for your language. Many frameworks give inbuilt debug tools that profiles to see where are performance issues
Several categories of tools:
wxites many tools are available
Could you define "performance bug" please?
Chrome Audit tab.
For things on the server side, it will depend on programming language, database, etc. Your DBMS may include logging options to let you know about any queries that are slow.
Here are some tools that you can use to find a performance bug
Performance bug Tools