Low throughput for sFTP over high latency high bandwith network

Our client (that uses ssh.net) runs on AWS and the sftp server is hosted on Prem, and our uploads are multi-threaded.
We use the default UploadFile() method, which through various tests seem to perform the best on this network.

We however are seeing that the performance is way below par when compared to the sftp command from openssh for a single thread.
Like 3 times slower.
And with multiple threads, it goes crazy slow, to the point that the total throughput from all the threads are lower than that it gets from a single thread.

OpenSSH's sftp command on the other hand scales quite well.

Open SSH has a patch called HPN-SSH for such networks, not sure if something can be inspired from that.

Inizia con il percorso predefinito UploadFile() del client SFTP e analizza un singolo caricamento su una rete ad alta latenza, quindi confrontalo con il comportamento di OpenSSH sftp descritto nell’issue. Riproduci il caso multi-thread e misura se il throughput aggregato diminuisce all’aggiunta di thread; il lavoro è completato quando la causa è stata identificata e il throughput è stato migliorato oppure la limitazione è stata documentata.