I was reading the doc about CPU Share but my question remains
If I want an app having less priority do I have to set the CPU Share higher or lower ?
such as, I don't really care if tiny tiny rss only respond when the CPU is idle
should I slide the CPU Share at 20% or at 80% ?
The CPU share setting is a percentage relative to each app. So, you should make tinytinyrss slider to be 20%. That way, it will take less CPU compared to other apps (which are set to default to 80%).
There's a more detailed explanation here - https://www.batey.info/cgroup-cpu-shares-for-docker.html . When 50%, we set the CPU shares value to be 50% of 1024, when 20%, we set the CPU shares to 20% of 1024 and so on.