// Attempt to use splice/sendfile() optimization, A very specific behavior mentioned below is necessary.
		// See https://github.com/golang/go/blob/f7c5cbb82087c55aa82081e931e0142783700ce8/src/net/sendfile_linux.go#L20
		// Windows can lock up with this optimization, so we fall back to regular copy.
		sr, ok := rc.(*sendFileReader)
		if ok {
			// Sendfile sends in 4MiB chunks per sendfile syscall which is more than enough