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关于各种内存的解释，来源于stackoverflow Wired : This refers to kernel code and such. Memory that should not ever be moved out of the RAM. Also know as resident memory. Shared : Memory that is shared between two or more processes. Both processes would show this amount of memory so it can be a bit misleading as to how much memory is actually in use. Real : This is the "real" memory usage for an application as reported by task_info() - a rough count of the number of physical pages that the current process has. (RSIZE) Private : This is memory that a process is using solely on it‘s own that is used in Resident memory. (RPRVT) Virtual : The total amount of address space in the process that‘s mapped to anything - whether that‘s an arbitrarily large space for variables or anything - it does not equate to actual VM use. (VSIZE) Active : Memory currently labelled as active and is used RAM. Inactive : "Inactive memory is no longer being used and has been cached to disk. It will remain in RAM until another application needs the space. Leaving this information in RAM is to your advantage if you (or a client of your computer) come back to it later." - Mac OS X Help Free : The amount of RAM actually available without any data. Some One Answer It‘s almost a year and I figured it out. clean memory clean memory are memories that can be recreated, on iOS it is memory of: system framework binary executable of your app memory mapped files Also notice this situation: when your app link to a framework, the clean memory will increase by the size of the framework binary. But most of time, only part of binary is really loaded in physical memory. dirty memory All memory that is not clean memory is dirty memory, dirty memory can‘t be recreated by system. When there is a memory pressure, system will unload some clean memory, when the memory is needed again, system will recreate them. But for dirty memory, system can‘t unload them, and iOS has no swap mechanism, so dirty memory will always be kept in physical memory, till it reach a certain limit, then your App will be terminated and all memory for it is recycled by system. virtual memory virtual memory = clean memory + dirty memory. That means virtual memory is all the memory your App want. resident memory resident memory = dirty memory + clean memory that loaded in physical memory resident memory is the memory really loaded in your physical memory, it mean all the dirty memory and parts of your clean memory. conclusion At any time, this is always true: virtual memory == (clean memory + dirty memory) > resident memory > dirty memory If you are worrying about the physical memory your App is taking(which is the key reason your App is terminated due to low memory), you should mainly focus on resident memory.
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原文地址：http://my.oschina.net/u/1782374/blog/499294
