In Sitecore 8.2 Update 4 we have unlimited cache setting. While we were in Update 3, had seen Memory leak issue but after applying Update 4 didn't see HIGH memory usage or memory leak.
Response time of the pages are also in acceptable range.
However, after upgrading to Sitecore 9.x during a LOAD test we noticed that Memory goes high and stay there almost 12 hours before it comes to normal. This is the case even with GC.
So why there is a different Memory handling in Sitecore 9.x?
Do you ever use unlimited cache, is it not recommended when you have sufficient resources and the site/content is not Huge?
Whats your suggestion?