As an example, I've noticed then when apt install is unpacking a package. It seems to stay at the same point for a very long time, and when I do htop, I see only 1 or 2% CPU usage, nothing really happening. Memory isn't full and Swap is not being used.
Anyway I can check what this bottleneck is? Using Ubuntu 16.04.4 and...
Linux odroid64 3.14.79-117 #1 SMP PREEMPT Tue Jan 2 23:46:30 BRST 2018 aarch64 aarch64 aarch64 GNU/Linux
Maybe I should check SD r/w speed?