I've been noticing some very strange RAM readings from my 2012 rMBP (8GB). In both Memory Clean and Activity Monitor, it's consistently showing as little as 7MB free, while the 'used' section includes up to 3.5GB of 'inactive'/'file cache'. The odd thing is, this seems to only happen when the MBP is plugged in, and it does not come with any noticeable slowdown or lag. I spent the last couple of days running on battery, and it almost never dropped below 5GB free, which is much closer to what I was used to, and the performance remained exactly the same in both cases. I'm not too worried, because there's no noticeable slowdown, but at the same time I can't help think it's not healthy to be running on what claims to be less than 10MB free out of 8GB. So, in the hope that someone else on here might have had a similar experience, or know why so much RAM is being assigned to the file cache only when the machine is plugged in, I thought I'd ask around. Any thoughts / suggestions / explanations?