How to understand why all the RAM on the VDS is clogged?

Question

linux

I have several sites on the VDS and there is a problem with full clogging of RAM and swap (approximately distributed like this):
1730MB php
983MB apache2 763MB
mysqld
62MB core

memory. Actually, it’s not clear whether the scripts are not optimized by php, or whether unnecessary processes may not end?

Answer 1

Limit the maximum amount of memory and the number of PHP processes, limit the memory available to the database. Change Apache to nginx, does it take a whole gigabyte?

Answer 2

You need to start using tools to monitor and profile the application for memory consumption and performance. For each YAP they are different. Plus there are Linux profiling tools. However, I would advise you to switch to them only after a thorough analysis of the application by means of the language.