This includes web browsers, especially if there are multiple tabs opened, 3rd party daemons, agents, and kernel extensions (which EtreCheck will show you), file sharing utilities such as, etc. Quit as many programs as you can when you want to run your virtual memory hog(s) and try not to run them concurrently if there is more than one. Since your Macbook Pro already has its maximum amount of RAM (16GB), you cannot give the operating system more RAM to work with, so you only choice is to reduce the amount of virtual memory being used by your Mac. If too many programs/apps request too much virtual memory the kernel runs out of memory it can devote to page tables. Each page of virtual memory requires the operating to have a page table entry to keep track of whether the virtual page is in memory and if so, what physical memory address contains your data, or if the page is in the original file (such as program code), and if so what file and what block of storage contains that page, or if the page has been paged out to a /var/vm/swapfile, and if so which swapfile and what block in that swap file. A) you do not have enough free disk space to create /var/vm/swapfile(s), BUT since you have 128GB of free disk space, it is NOT that.ī) The other, is that the collections of programs and apps is using more virtual memory that the operating system can manage. A lot has changed, but some core principles have remained unchanged. I worked on my first virtual memory hardware back in the 1975 timeframe (I was writing a virtual memory hardware diagnostic program for manufacturing testing). You know, not everybody like onions.įully understanding virtual memory is like an onion □Īnd to keep it interesting, every operating system has slightly different approach to its implementation, so of that because of the CPU's virtual memory hardware, and some of it because that is how the operating system was written. You get it? We both have layers.ĭonkey: Oh, you both have layers. Only user modified data gets paged to the swapfile(s), so I do not have humongous swapfile(s) being created.ĭonkey: Oh, you leave em out in the sun, they get all brown, start sproutin’ little white hairs. Also all the program code is stored in the programs executable file. counted, as shared library/framework code only has one set of page tables that every process gets to share, but my counting method does not take that into account, as my counting method is rather simple minded. NOTE: A lot of the virtual memory I'm showing is double/triple/quad/. My Mac was using 13GB of physical RAM (RSS) and 880GB of virtual memory (VSZ). Just to give you an idea of how much virtual memory can be used, I ran the following command from a Terminal sessionĪnd then added up all the RSS and VSZ entries. That is what the page tables do.Īt what point do you want to give all the RAM to the operating system so it can manage page tables and none of the RAM to applications, so you end up spending all your time moving pages to/from storage attempting to use the hand-full of pages not being taken up by virtual memory page tables? Any you need a "Buried Treasure Map" to find all the bits, for all the applications, and where they have been stored. The amount of virtual memory exceeds the physical amount of RAM by orders of magnitudes. So wash/rinse/repeat for every process listed in Activity Monitor -> View -> All Processes, and you will find that the amount of virtual memory being used is huge.Īnd if it is not clear yet. Now repeat that for every process, and eventually you are consuming a lot of physical RAM just to manage the page tables.įor example if a page table entry takes 128 bits (16 bytes), that 1,128,840 page table entries would consume 18,077,440 (about 17MB of RAM). That is 1,129,840 (million) page table entries. You will notice that the physical memory being used in 392.9MB, but the virtual memory being used is 4.31GB.Įvery 4K of that 4.31GB needs an entry in the operating system page tables to keep track of where that 4K lives. Select process (app), and use Activity Monitor -> View -> Inspect Process -> Memory (or select process, Command-I (command-eye), or select process and click on the ℹ (info) button in the Activity Monitor upper left edge of the window) You can still see virtual memory usage for a process via Activity Monitor. Secondly It may seem like a daft question but how do I identify a virtual memory hog? Activity monitor shows memory for processes but none appear to be particularly large.Īctivity Monitor used to have a virtual memory column, but they did away with it a few operating system release ago. Thus the MacBook would likely slow down but not stop completely (which is what appears to happen). I always thought that the point of virtual memory was that it would be swapped in/out of disk provided that there was available disk space.
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