OSX keeps track of what this is and what it belonged to because of the idea of temporal locality, the idea being that if you opened an application you are somewhat likely to do so again and if the memory is still labeled, the application can start very quickly. Inactive memory is memory that has recently been used by an application that is no longer running.
#Ifreemem pc free#
If there is no inactive, or free memory, active memory can be used by other applications, but this causes the OS to write the current state of the active memory being traded to its owner's virtual memory pages on disk before granting the memory to another application. Since we are talking about the amount of RAM in use, we won't worry about virtual memory for the moment. If you look at a running process in the Activity Monitor list, you'll see a column for Real and a column for Virtual Memory. Note that thanks to the splendors of virtual memory, all of the memory needed by an application isn't necessarily contained here. Another application can't "borrow" wired memory.Īctive memory is what is currently in use by running applications.
Wired memory is used by the OS and is pretty much untouchable. OSX labels physical memory (RAM) as follows: Wired, Active, Inactive, and Free. If you open the Activity Monitor (found in utilities) and select the "System Memory" tab at the bottom, you'll see something that looks roughly like this: A friend of mine (Quinn) helped illuminate some of this for me. It turns out that the bug was in my understanding of how OSX uses-and labels-memory. Concerned that I had some kind of memory leak going on I started digging around to find out where the "bug" was. I happened to look at a resource monitor widget I had in my Dashboard, and was immediately concerned that I was only showing around 100 Mb free RAM. A couple of weeks after I got my MacBook, I was working one day on a programming project for school with nothing open but iTerm and a couple of gvim windows. There were others, but this is the one that leads to this discussion.
#Ifreemem pc windows#
One of the reasons I originally switched from Windows to Linux was resource efficiency. I have been a linux user for a few years, and I recently (6 months ago) switched to a MacBook.
I'm leaving this post as-is for historical reasons, but if you're running Mavericks you'll see things pretty differently. Edit/Update: Modern releases of OS X (Mountain Lion and particularly Mavericks) treat memory much differently.
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