Upload & Sell: Off
OK after reading some more it is my understanding that OSX keeps all memory allocated by currently running applications but not recently used, into "Inactive". But these are running applications, not applications that have been closed again.
So if there is no Free memory left, and all memory is either Wired, Active and Inactive, all memory is in use by my applications and I've filled the 12GB of RAM. Opening more programs causes the system to write chunks of memory from the RAM (inactive section) to the hard drive to free up RAM for my new program. The Page-Outs start to rise.
So far so good. Well not good, but I understand it, at least. That is, if I interpreted it correctly.
How come my RAM seems to fill up much more than the physical RAM used for my applications? I did a test:
- Rebooted and checked Activity monitor. 600 MB used.
- Launched Firefox and Lightroom 4.1. According to Activity Monitor, LR eats 1.4GB and Firefox 330MB. That's 1,73 together. Still Free RAM fell to 8.27 GB, so 3.73 is in use. How come?600MB + 1.73GB = 2.33 GB, not 3.73.
- I can go on with other programs, the sum of the physical memory is not the amount of used memory.
Anyway, when the page-outs keep appearing, it's time to add memory. Whether the math is right or not (well I suppose the math is always right, but I just don't understand zip of it).
Assuming that 16GB will be enough for my usual workload, one would think that adding 1 4GB module will do the trick. However, the system will be slower because 3 modules (of any given identical size) works fastest in this configuration. So for best performance, I should upgrade to 3x8=24GB RAM.
But that's much more expensive AND I need to order it from the USA because in the Netherlands it costs about 155 € (180$) per 8GB chip, so 560$ for 24GB. OWC has an upgrade kit for 245$.
I'll have to give this some thought......