Yes, I remember when I was a UNIX user, and first started using Linux. The first thing I thought looking at "top" output was where did all the free memory go. There was all this cached memory, and little "free" memory. Didn't take long to find out that I had lots of free memory, it was being used as permitted as a cache for previously loaded software. So that software wouldn't have to be reloaded if needed again. But that cached memory was available for re-use if needed. Good strategy, using available memory to speed up running programs, I like that.