Ok... so I just got a new rMBP with 16 GBs of RAM. Yesterday I checked activity monitor to see how much RAM I was using and it said 9 GBs. This was with Firefox,itunes,mail,adium (aim client), terminal, maybe pages (don't remember), messages open. Today I opened it after some one pointed out that with as fast as applications load, you don't need to have everything open at once (which made me think he has a point, I'm so used to having everything open but when he pointed that out I realized it was cause things took so long to load). So I closed the mail app (and I don't have pages open right now) and checked activity monitor and it says I am using 15.99 GBs of RAM. WTF?! (I already thought it was a bit weird yesterday it said 9 GBs when I've been running the same stuff except replace Pages with MS word on my previous Macbook with only 4 GBs of RAM. But I figured maybe that was why my computer was so laggy). It's not saying there is much memory pressure yet and it hasn't used any swap yet. But I'd rather it not use swap (I hear that reduces your life of your flash storage). The biggest usage of RAM is from Kernal_task with 972 MBs (firefox unsurprisingly second at 410). So is it normal to just fill up the RAM usage? Or should I worry that i have something hidden that is taking up RAM on my computer (entirely possible, I used migration assistant to just get all the software over on this one and have it mirror my old one. And I did the same with the old one from my previous computer. So I haven't done a fresh install in like 7 years?).