Factorio Forums

For context, I have fiber to the home at high speed (gigabit or so). But while inside factorio, downloads (eg: large mods, or game updates) are often self-throttling to about 3 megabytes/second. I know it could go faster because the TCP receive buffers are highly full when I check them:
I also tried direct downloading the same content from a linux shell (factorio logs contain the URL, and I have my own authentication token). I can hit full speed consistently. However the game itself throttles.

My speculation as to a reason is that the menu screen still runs at 60 fps and as a result the network buffers are only checked periodically, resulting in a lot of available bandwidth being left on the table.

I am not able to reproduce any such issue when downloading huge mods in-game. I suspect this might be operating system socket specific (I'm on windows)?

I also cannot reproduce because Factorio is able to saturate my 200 Mbit/s internet connection. Your conjecture might be correct - we update libcurl on the main loop which only runs 60 times per second. Perhaps moving it to a dedicated thread would help things, but that is a fairly invasive change to fix a relatively minor issue.