OpenVPN performance boost observation

[robi]

I've noticed drastic improvements on file transfers through OpenVPN, between two sites using the same Supermicro A1SRi-2758F systems, running both pfSense 2.3.2 64-bit, by just adding these lines to both client and server:

sndbuf 0;
rcvbuf 0;
fast-io;

[heper]

–fast-io
    (Experimental) Optimize TUN/TAP/UDP I/O writes by avoiding a call to poll/epoll/select prior to the write operation. The purpose of such a call would normally be to block until the device or socket is ready to accept the write. Such blocking is unnecessary on some platforms which don't support write blocking on UDP sockets or TUN/TAP devices. In such cases, one can optimize the event loop by avoiding the poll/epoll/select call, improving CPU efficiency by 5% to 10%.

This option can only be used on non-Windows systems, when –proto udp is specified, and when --shaper is NOT specified.

[robi]

Well, site-to-site connections provided by OpenVPN on pfSense certainly qualify for that option.
Plus, the option can be used on pfSense as server, while Windows clients can stay as they are (without this option).