Ask HN: What tools do you use to analyse server performance?

At one end there are many website and web-app performance analysis tools, at the other there are lots of low-level Linux performance tools (e.g. eBPF), but what tools do you use to analyse your application's performance (when looking to optimise it)?

This might include profilers, production server monitoring, static analysis tools, etc. They can be language specific or not.

What are you using day-to-day/week-to-week/month-to-month?