Why performance doesn't improve under Link Aggregation mode?
Due network communication protocol limited, the link aggregation have advantage for multiple client trans data during heavy loading period, thus we can’t get perfromance advantage via single client.
And following link & chart for your reference:
https://delightlylinux.wordpress.com/2014/07/12/speed-up-your-home-network-with-link-aggregation-in-linux-mint-17-and-xubuntu-14-04/
EX: Typical Gigabit LAN
https://delightlylinux.files.wordpress.com/2014/07/net0331.png?w=620&h=428
EX: 2 Gigabit LAN with Link Aggregation
https://delightlylinux.files.wordpress.com/2014/07/net0341.png?w=620&h=515