Compressed, physical memory which hasn’t been used recently, so has been compressed to save space.Wired Memory, physical memory which can’t be either compressed or swapped out to disk, which should include all that being used by the GPU in Apple silicon Macs.App Memory, the total amount of physical memory allocated to system processes and apps, which might or might not include that being used by the GPU in Apple silicon Macs.Memory Used, the total amount of physical (real) memory being used by the system and apps, which for Apple silicon Macs should include that being used by the GPU.The breakdown given at the foot of the Memory view includes: Memory used is broken down into App and Wired memory, and the amount that’s compressed to save space. Looking at the detail at the foot of the window, you’ll see a value for the physical memory installed in your Mac, how much memory is used, whether there are any files which are cached to disk storage, and any swap memory usage. With my normal working apps open, the largest user of memory is Postbox, but none takes more than 600 MB. Confirm that the window title reads Activity Monitor All Processes. In the View menu, ensure that All Processes is ticked, or system processes will be hidden. Activity Monitor provides a good overview and plenty of useful detail on memory use in its Memory tab, particularly when you list processes in order of their memory use, by clicking the column header Memory to sort them with the largest at the top. The remainder of main system memory is available for use by apps and other processes, and is our main concern here. Investigating Mach zones isn’t easy: the best way to get an overview is with the sudo zprint command. This last happened in a release version of macOS back in Catalina 10.15.6, and caused kernel panics. There are hundreds of different zones, each of which is allocated early during the kernel phase of booting.Įxceptionally, the kernel or one of its extensions can leak memory from these Mach zones, by using it but failing to free it properly. These consist of pools of pre-allocated memory in a range of fixed sizes that can be used very quickly. To do that, and its other functions, the kernel dedicates some memory for its own use, and use by kernel extensions, known as Mach zones. Managing system memory is one of the main tasks of the macOS kernel. This article concentrates exclusively on main system memory. There are also smaller specialised memories dedicated to the support of specific chips, such as cache memory for CPU cores. Intel Macs may have separate graphics memory, if they have a separate graphics card, or that memory may be allocated from main memory, in which case it doesn’t work the same as Unified Memory. If you have an Apple silicon Mac, you’ll be aware that it has Unified Memory, which means that, instead of having dedicated graphics and other memory in its chip, (almost) all its memory is in one place, where it’s accessed by the CPU, GPU, and other systems such as the Neural Engine. This article concentrates on basics, aiming to improve understanding so you can tackle memory problems better. Now we can’t do that, making the most of the memory our Macs have becomes even more important. When most Macs could have their memory upgraded, one of the most popular ways to improve performance was to add more memory modules. Memory is one of the most precious resources in our Macs, and one of the most complicated to understand and manage.
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