What causes the problem with the limited speed of the Transmission torrent client?

Question

Computer networks

I noticed a problem in the limited upload speed in the subject client.
Despite the gigabit network, the speed is exactly 7.98MiB/s. Peers are local, mostly gigabit links. But it does not rise above this value. Limits, of course, are disabled. I thought the problem was in the hardware, and something cuts the speed, but even on the localhost 2 clients drive traffic between neighboring sockets at the same speed. The effect is the same on different versions, including building from SVN. Played with buffers, slots, and other settings. Didn't give any results.
The problem is in the distribution (upload) from this client. If we take, for example, rtorrent and distribute from it, and receive it with transmission, then it gives out about 30-35 MiB / s, which is more or less acceptable.
Maybe someone came across? The problem is that I can not change the client, for reasons beyond my control.

Answer 1

Maybe the screw does not cope, did you look at the load on it during the distribution?

Answer 2

net.core.rmem_max and net.core.wmem_max
configured?
https://falkhusemann.de/blog/2012/07/transmission-...