Why is there a large loading of the site on Bitrix?

Question

Apache HTTP Server

Good afternoon!
The site on Bitrix, for some reason, is always a big load - 85-90% of RAM from 16GB is eaten. Site traffic is not very high. Bots were blocked to the maximum through .htaccess, leaving only search engines.
When you restart Apache, the RAM is cleared, but within 2-3 hours it again reaches the 80-90% bar.
Tell me where to dig?
Atop showed the following picture:

Answer 1

As far as I understand, you just use memory for the cache, which is excellent. If necessary, system resources are instantly released.