I searched on this forum, and i do see this question came up before, but I still think this worth mentioning.
I am not here to question why it would current implementation takes that much memory.
My Sync Folder contains about 56632 files, and folders are: 575GB in size. Running on Ubuntu 16.04 and rslsync uses about 9.1 GB RAM. (CPU fluctuates between 5-8% during running)
For a comparison, i also use Dropbox Pro, I have 26602 files and 79GB in size. Dropbox uses about 329MB RAM. (0 % CPU when idle)
In this case, since server is powerful enough that I don't care about the RAM and CPU. But on a less powerful machine, it is also very resource intensive.
I have a laptop running windows, upon start, Sync eats 5 GB RAM, (this is given the fact only one folder (less than 200MB) is in full sync mode, most others are selective sync and with very few files synced).
When Sync finishes initialization, it stables at 2GB RAM. (At this point I have effectively 2.25GB data synced, Folder properties shown 113k Files). And CPU usage flucuates around 20-50% (this is a much weaker processor i7-4510U)
This is a LOT of resources for such small number data being synced in selective sync mode.
Again I am not here asking why it is so, or I am trying to say this is a bug. I think this huge resources footprint will greatly limit Sync's user base/ usage. And it simply cannot compete with Dropbox as a standard family sync tool. (All your photos, 4k videos etc, old backups of your OSes).