In SERVER-81784, Mathias suggested investigating MSG_ZEROCOPY along with MSG_WAITALL:

Could also investigate using MSG_ZEROCOPY with large messages to keep the Message object alive until the kernel knows it won't need it while allowing the kernel to avoid doing its own copies. They claim it is only beneficial for messages >10KB.

Splitting this into its own ticket because I think it warrants its own investigation (after looking at it for a bit, I think we would have to determine a threshold for message size at which it would be a useful flag to set)