Posting again here as previous post was deleted from r/cpp.

I have a low latency Linux application that uses Boost ASIO to communicate over TCP to upto 100000 servers in async way. This application is a client to all these TCP servers.

Currently, I call io_service.run() from [2 * number of core] threads to process IO to/from peers.
I know internally, ASIO would create an epoll on single fd for the io_service and the calls to run from threads would have contention around queue polling.

I wanted to know how to understand if having a single io_service, albeit spread across multiple threads, could be a potential bottleneck.

Is io_service, limited by:

1. epoll
2. Contention on internal queue

Note: changing application to use multiple io_service is bit involved, hence could not do a quick POC as of now.