Excessive use of memory

Question

Why it's 3.5Gb is used, when I can see only 0.68+0.12+0.11+...=about 2Gb ? The same situation is observed when 7.9Gb is wired, but only 4Gb is really used by applications?

Answer 1

Wired is NOT all of RAM.  The memory in use is Wired+Active+Inactive
The Inactive is basically a cache which can be released and given to processes.  However, if something in the cache is needed again, it is much faster to either give the page(s) to the app direct from the cache or copy it from the cache, rather than read it from disk (even a solid state disk).
If you are going to go around adding up Real Mem usage, then you have to A) set the process pop-up to "All Processes", and B) scroll down to the bottom of the list to see every process.
Or you could run the following shell command from  Applications -> Utilities -> Terminal
ps -o rss -ax | awk '{sum += $1} END{print sum/1048576 "GB"}'