How to increase speed inside GNS3?

Question

Computer networks

Good day!
There is a test stand
of 3 routers simulating the Internet, and 2 hosts - virtual machines from 2 ends.
OSPF routing configured.
When transmitting TCP traffic, the speed between hosts is 140Kb / s (tested on ftp, as well as using scp).
Tell me how to raise the speed to normal or is it a feature of gns3?