First of all, if you have multiple processes trying to read/write the same config, that's kind of suspect, and if file I/O is a bottleneck for your config system, that's a different suspicious situation. Why are your processes writing to the config so... often?

But regardless, I can't see how those problems get immediately better by storing that config in a single file. If anything, having it split across multiple files would improve the situation, as different processes that might only be concerned with different sections of the config won't need to wait on file locks from process unrelated to their concerns.