• I have searched the issues of this repository and believe that this is not a duplicate.
• I have checked the FAQ of this repository and believe that this is not a duplicate.

Environment

• Dubbo version: master
• Operating System version: windows
• Java version: 1.8

In ExtensionLoader, EXTENSION INSTANCES is a ConcurrentHashMap with a default size, and the extension class provided in Dubbo has exceeded 16.
Start the program, it will expand at least twice. I think it is more appropriate to add an initial size of 64 here.
Other places where ConcurrentHashMap is used should also pay attention to a suitable initial size