I've read a lot about commit charge and something still is bugging me. On my mac (and probably on linux too), what is the relation between VM size and and Commit memory (windows). I think I fully understand commit after some testing, but in windows it doesn't seem that the amount of virtual memory ever exceeds the swap space + ram. IN OSX (and linux) the VM size seems to almost exceed the size of my harddrive! I'm guessing it either includes shared memory more than once, or it includes allocated but untouched or written to memory. Let's say I make a malloc(2gb) (obviously not like this), is different from actually writing to that entire 2gb.
So this brings me to my question, what exactly is VM size measuring in OSX and linux. Is it a total of all the malloc calls for example (or total possible VM for instance, including practically 4gb for each process on a 64 bit machine), and how does this compare to the Commit (limit,peak,use) on windows? Does windows not let you allocate more than your swap + ram limit, as OSX and linux do and why?
In the images below you can see that in windows swap + ram equals commit (2gb). In OSX my VM size is over 200gb on a about 200gb harddrive.