Major performance issues running gitlab

Hi, we are using gitlab 12.0 with CI and registry, and ci-runners in an external machine. We have 30-40 users and gitlab is running on a host on aws with 8GB ram (m3_large).

I find myself in need to restart the service at least once a day when it becomes amazingly slow. I wonder if there are any recommendation or best practices that i'm missing.

Btw, i installed the omnibus package ...