Currently Cyberduck is a huge resource hog on my uploads. I'm a Backblaze employee and doing this from our office where we have ample bandwidth on our network. Attached are screenshots on the memory being allocated to Cyberduck (60GB... note my laptop has 16GB RAM) and with regular CPU usage of 350-467 %CPU. I'm at the point that it looks like the memory required to run Chrome and Cyberduck concurrently is causing problems. I've got it down to a 1 window margin where the application freezes if I open one more tab and works again when I close a tab.
Not sure what is causing the problem but you'll want to look into it.
With two transfers and the transfer concurrency set to 9 you will have 18 threads running for uploads. Please try to set a lower value for the number of connections allowed for transfers to lower CPU usage.
Even reducing the threads this is happening. The longer the app is open as transfers happen the more the memory allocation grows and grows. I'm trying an upload this morning and the app memory allocation quickly skyrockets even after an upload fails. Trying the upload again the memory allocation continues to grow. My upload is now at 41GB in memory allocated. Based on past experience when it hits 60GB on my machine it will crash it.
We could pin this down that this is not an issue when running in a sandbox. Somehow when requesting security scoped bookmarks and not running within an application sandbox is leading to this massive memory leak. Thus, the Mac App Store version should not be affected from this.
I also suffer from memory hogs (I have 84 bookmarks) on MacOS a long time now. Installing the latest snapshot didn't cure anything. Just opening CyberDuck without any connections alive, uses more than 1.1GB of memory.