Why the function consume the message from service bus topic so slowly?

Hi,

I created one function app to consume message from service bus, then import to cosmos DB, everything is ok, but the only problem is that the function consumes the message in service bus topic so slowly.

1. this is the function app configuration





2. this is the cosomos DB configuration


3, this the service bus topic, you could see, it assemble so many message, I tested, it seems that it only consume 50-60 messages/sec, even less if there are more message send to the topic.


What I want to do is correct, the message can be sent to the topic, function app can consume the message from topic and import to the cosmos DB, but it is too slowly.

Anything I did wrong for the configuration? Please tell me how to make it more quickly.

Thanks