Increase / Improve / Speed Up Renderung Performance

Hello Everybody,

i try to Create my Own Tileserver.

But it is soooo slow.

Therefore i use render_list to pre_render Tiles.

But why is it so Slow?! And only 740 MB of 5,4 GB are used (13 %)

I am running it on a VM. If i only use it for Belgium / one County → it is fast.

But Hole Europe → Slow

How can i improve the Performance? Please dont tell me use more RAM. You can tell me if there is no more Free RAM left. Ore a better CPU (4 Core, every usage unter 15 %)