On Jan 3, 2006, at 11:44 AM, R. D. Preston wrote: > Is anyone up for a convo concerning System Memory? ? and why my > 'Inactive' > memory grows, while the 'Free' memory slowly dwindles to the point > of being > exhausted. I've noticed this while watching 'Activity Monitor' in > System > Memory mode during my modem-hangup problem.
What you're seeing is normal and desirable behavior for a Unix system. All Unix systems try very aggressively to use all your RAM all the time. The idea is that unused RAM is being wasted, so they cache all sorts of useful things there, such as recently opened files, system libraries and networking information. This RAM can be freed up very quickly, if it is needed by a program. In the mean time, it is available hundreds of times faster than through a disk access. You can look at the memory allocation by opening up a terminal window and typing 'top'. Here's part of what my PowerBook shows: PhysMem: 64.3M wired, 122M active, 286M inactive, 474M used, 550M free VM: 3.83G + 128M 26028(0) pageins, 0(0) pageouts Here's what each of the categories means: wired This is memory that's used all the time and is never freed up. It's where the operating system kernel lives. active This is allocated for use and has actually been used recently. inactive This is allocated for use, but has not been used recently.. used wired+active+inactive free Not yet used for anything. Since the power died last night, I just rebooted the machine for the first time in ages. That's why the free memory is so large. as I continue to use the machine, more stuff will get cached, and the free memory will dwindle. This is a good thing because frequently used data is being cached. As this happens, the whole system speeds up because your machine doesn't have to go to the slow hard drives as often. This is one reason why I hardly ever shut down a Mac OS X machine. People who shut down their machine every night may be taking a performance hit. Don't worry about your memory unless the pageouts number in the top display gets big. This is the indicator that shows you're using all your RAM and then some. Here's the same top information 10 minutes later. All I was doing in the interim was reading email, typing this message and printing a pdf. PhysMem: 66.4M wired, 226M active, 552M inactive, 746M used, 350M free VM: 3.94G + 128M 26868(0) pageins, 0(0) pageouts | The next meeting of the Louisville Computer Society will | be January 24 at Pitt Academy, 6010 Preston Highway. | The LCS Web page is <http://www.kymac.org>. | List posting address: <mailto:macgroup at erdos.math.louisville.edu> | List Web page: <http://erdos.math.louisville.edu/macgroup>
