Windows任务管理器中的内存是什么鬼

 

PC Magazine：Apparently, a certain amount of virtual memory has been "committed." As for "charge," who knows? What we do know is that people who come up with such names should be "committed" to a place prohibiting them from creating user interfaces.

请求分页系统建立在基本分页系统基础之上，为了支持虚拟存储器功能而增加了请求调页功能和页面置换功能。请求分页是最常用的一种实现虚拟存储器的方法。

“请求”二字不知谁给加得。In computer operating systems, memory paging is a memory management scheme by which a computer stores and retrieves data from secondary storage for use in main memory. Paging refers to writing portions, termed pages, of a process'memory to disk. Swapping /swɔp US swa:p/, strictly speaking, refers to writing the entire process, not just part, to disk. In Linux, true swapping is exceedingly rare, therefore the terms paging and swapping often are used interchangeably.

    

Commit charge is a term used in Windows to describe the total amount of virtual memory of all processes that must be backed by either physical memory or the page file. Windows' pagefile.sys functions as virtual memory, which allows your computer to swap information between system memory and your hard drive. Through the process of paging, the contents of the virtual memory may move between physical memory and the page file, but it cannot exceed the sum of sizes of those two.

• Total is the amount of pagefile-backed virtual address space in use, i.e., the current commit charge. It is composed of main memory (RAM) and disk (pagefiles). The corresponding performance counter is called "Committed Bytes".
• Limit is the maximum possible value for Total; it is the sum of the current pagefile size plus the physical memory available for pageable contents (this excludes RAM that is assigned to non-pageable areas 如DMA缓冲区或内存映射IO). The corresponding performance counter is called "Commit Limit".
• Peak is the highest amount that the total commit charge has reached since the operating system was last started.

目前还没有字典说commit能做名词。charge倒是和amount, load等沾边。commit:  give or transfer sb/sth to (a state or place) for safe keeping, treatment, etc. OS commits data to RAM and disk? charge解释为电量的量? 也许commit charge应译为委托量或托付量。甭用commit charge, total virtual memory不好吗？TVM也行啊。:-)

Virtual memory not related to commit charge includes virtual memory backed by files and all-zero pages backed by nothing. Virtual memory backed by files是MapViewFile得到的东西。All-zero pages等有人开始往里写了再分配：lazy initialization is the tactic of delaying the creation of an object, the calculation of a value, or some other expensive process until the first time it is needed. It is a kind of lazy evaluation that refers specifically to the instantiation of objects or other resources.

Commit charges (3个所以用复数) may also be displayed as percentages. 百分比只有2个，Limit / Limit ≡ 1.

The program Process Explorer reports the same set of values, labeling the Total as Current, and additionally providing percentages of Peak and Current towards the Limit value.

The commit charge increases when any program is opened and used, and goes down when a program is closed. It will also change when already-running programs allocate or free private virtual memory; for example, with the VirtualAlloc and VirtualFree APIs.

In the Task Manager utility under Windows XP and Windows Server 2003, the graphical displays labeled as "PF usage" and "Page File Usage History," despite their labels, reflect not the pagefile contents but the total (or current) commit charge. The height of the graph area corresponds to the commit limit. These do not show how much has actually been written to the pagefile, but only the maximum potential pagefile usage: The amount of pagefile that would be used if all current contents of RAM had to be removed. In Windows 2000 and Windows NT 4.0, these same displays are labeled "Mem usage" but again actually show the commit charge and commit limit. Similar displays in the Task Manager of Windows Vista and later have been changed to reflect usage of physical memory.

In Task Manager's "Processes" display, each process's contribution to the "total commit charge" is shown in the "VM size" column in Windows XP and Server 2003. The same value is labeled "Commit size" in Windows Vista and later. The total commit charge will always be larger than the sum of these values, as the total includes system-wide allocations such as the paged pool.

In the same display, the "Mem Usage" column in Windows XP and Server 2003, or the "Working Set (Memory)" column in Windows Vista and later, shows each process's current working set. This is a count of physical memory (RAM) rather than virtual address space. It represents the subset of the process's virtual address space that is valid, meaning that it can be referenced without incurring a page fault.

The commit charge for each process does not include other major contributions to the process's virtual address space, such as mapped files. For this reason, the process's working set (the portion of its address space that can be referenced without incurring a page fault) may be larger than its contribution to total commit charge, and the total commit charge is not inclusive of the total memory (physical or virtual) actually in use.

The commit limit may be increased by either creating additional pagefiles or, if pagefile expansion is enabled, by expanding an existing one. The operating system will expand the pagefile automatically, if possible, when the total commit charge approaches the limit. In such an event a popup window will be displayed stating that "The system is running low on virtual memory."

If the system ever runs completely out of commit charge (that is, if the total reaches the limit), a popup window will be displayed stating that "The system is out of virtual memory," and it may become extremely sluggish or even nonresponsive. Closing programs (if the user is still able to do so at this point) decreases the total commit charge and may thereby free up the system.

Windows 任务管理器中的几个内存概念 | Pushing the Limits of Windows: Virtual Memory

六级/考研单词: commit, prohibit, compute, retrieve, data, portion, swap, strict, thereby, seldom, physics, compose, correspond, assign, tactic, expense, evaluate, allocate, utility, usage, despite, graph, valid, incur, decrease