Optimise GC and `jemalloc` of all other processes other than GitLab Rails
Related to:
We currently run a number of sibling processes that are not GitLab Rails as part of Omnibus.
We should ensure that their settings are optimised to conserve memory. This includes:
- Gitaly: Go + Ruby (GC settings, jemalloc)
- Workhorse: Go (GC settings)
- GitLab Exporter: Ruby (GC settings, jemalloc)
- PostgreSQL: C (like shared_buffers)
- Prometheus: Go (GC settings)
- ...
Currently, they run with defaults, but it appears that we can free a dozen MBs if we make the settings more tuned to smaller instances.