System PTEs can theoretically describe up to 2GB on x86 system and 128GB on 圆4 systems. Page Table Entries are a pool of PTEs used to dynamically map system pages such as I/O space, kernel stacks and the mapping of memory descriptor lists. : Page Table entries allow the mapping of virtual memory addresses to physical memory addresses. Kernel pooled memory that cannot be paged to disk. : Kernel pooled memory that can be paged to disk. Page tables contain PTEs (Page Table Entries), which describe virtual address usage. Pages that have been marked as shared can be used by multiple processes. For more details on mapped files, see the references at the end of this post. This can be a process mapping views of files into its memory (for reading or writing) or for the system file cache. Memory allocated for use only by a single process.Īlso known as section objects, mapped “views” of files are when the contents of that file are mapped to virtual addresses in memory. These are physical pages that have been marked as bad. This zeroing is periodically done at a low priority by the memory manager’s zero thread, or it can be done on demand when larger numbers of pages are needed and the zero list becomes exhausted. Contrary to the general notation of free memory being good, when you are looking at the Free list here, keep in mind that these pages will be put on the Zeroed list so they are one step closer to being used. These are usually pages that have been freed by an exiting process. After the system has “settled in” you will likely see these pages being put to good use somewhere on the Standby list as cache.įree pages are free to be used but have some type of “dirty” data in them so they must be zeroed for security reasons before given to a user process. You will usually only see a significant amount of Zeroed pages after a system is booted. Pages that have been zeroed out and are ready to be used – they can be quickly allocated for new physical memory allocations. Pages that are in transition between any of the other categories. Similar to modified pages but have been marked not to write out to disk. Similar to Standby, but these are pages of physical RAM that have been changed and must be flushed to disk before reusing them. Standby pages are essentially cache – it’s better to have infrequently used data kept in RAM “just in case” than pushing it out to disk when the memory isn’t needed for anything else. These are still left in physical ram but will be repurposed first by the memory manager (either returned to the active list or zeroed out and reused) if something needs physical ram for active pages. Pages of physical ram not actively being used. Pages of physical ram in active use by the specified category (usually a process working set or the system working set). Memory management is a complex beast, so let’s run through a quick refresher of these categories. It allows us to examine detailed memory usage information in a way that is easy accessible.Įach tab has its own wealth of data, but I’ll be focusing on Use Counts and File Summary tab as they offer the information I think most people will be interested in. This tool is called RamMap and it is available from SysInternals at I’d like to talk a bit about a new tool that allows us to examine a vital performance resource: physical memory. My name is Ray Ackley and I’m a Support Escalation Engineer in the Performance specialty. Hello everyone, I’d like to introduce myself. First published on TECHNET on Aug 13, 2010
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