If I may, one additional thing that I found which helps a lot with memory issues as relate to MySQL: Use jemalloc or similar. Essentially I brought a system whi

If I may, one additional thing that I found which helps a lot with memory issues as relate to MySQL: Use jemalloc or similar. Essentially I brought a system which killed off the MySQL service every few weeks in OOM, to running faster than ever and never having memory issues. That isn't to say it's a substitute for full troubleshooting, but as a first step, using a different malloc routine can sometimes help quite a bit!