BorlandTalk.com Borland discussion newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  Pagefile (swapfile) size          BorlandTalk.com Forum Index -> C++ Builder (Non-Technical) View previous topic :: View next topic   Author Message Nate Lockwood Guest Posted: Sun Sep 11, 2005 4:54 pm    Post subject: Pagefile (swapfile) size Recently I've been having problems with a third party application that takes lots of memory; XP says it's adjusting page size and everything slows down or freezes for a while. I suspect that the application asks for even more memory and XP allocates it etc. Since I had only 356 MB RAM I upgraded to 1.5 GB and the problem went away but I started thinking about swapfile size since I remembered that the size of the swapfile was related to the amount of RAM. Her is what XP Help says: "Managing computer memory When your computer is running low on random access memory (RAM) and more is needed to complete your current task, Windows uses hard drive space to simulate system RAM. In Windows, this is known as virtual memory, and often called the pagefile. This is similar to the UNIX swapfile. The default size of the virtual memory pagefile (appropriately named Pagefile.sys) created during installation is 1.5 times the amount of RAM on your computer." Now why would I need even more swapfile space with more RAM? I would think that the more RAM I have the less swapfile space I would need or that no matter how much RAM I have the required swapfile space would depend on how many concurrent processes are running and how much memory they want. Just curious. Nate Back to top Andrue Cope [TeamB] Guest Posted: Mon Sep 12, 2005 7:56 am    Post subject: Re: Pagefile (swapfile) size Nate Lockwood wrote: Quote: Now why would I need even more swapfile space with more RAM? I think it's because of the way Windows handles virtual memory which is a bit different to traditional systems. In traditional systems the 'swapfile' is where things end up when there's no RAM available to hold them. Basically they get squeezed out and end up on disk. In this scenario the swap file can be kept small. Adding enough RAM can actually make the swapfile redundant. Windows has a different strategy. In Windows RAM is reserved for things that are currently needed and less active data is proactively moved out to disk. In this case the swapfile will always be being used and adding more RAM implies that more swapfile is required as well. -- Andrue Cope [TeamB] [Bicester, Uk] http://info.borland.com/newsgroups/guide.html Back to top Nate Lockwood Guest Posted: Mon Sep 12, 2005 3:01 pm    Post subject: Re: Pagefile (swapfile) size Andrue Cope [TeamB] wrote: Quote: In Windows RAM is reserved for things that are currently needed and less active data is proactively moved out to disk. In this case the swapfile will always be being used and adding more RAM implies that more swapfile is required as well. Thanks, Andrue, that makes sense. Does that mean that data can exist in both places so that data in RAM can be used if it has not been over written? Nate Back to top Andrue Cope [TeamB] Guest Posted: Mon Sep 12, 2005 3:40 pm    Post subject: Re: Pagefile (swapfile) size Nate Lockwood wrote: Quote: Does that mean that data can exist in both places so that data in RAM can be used if it has not been over written? Yes, according to 'Inside Windows NT'. A page frame is zeroed before reuse (so as to adhere to the DoD C2 rules) but like most operations it is on-demand or 'lazy initialisation'. When a frame has been swapped out it remains in a 'Standby' state and can be reactivated. As I understand it each frame of a process (4kB chunk of its address space) has a PTE (Page Table Entry). The PTE indicates whether or not the frame is backed by RAM and if so, where it is. When a frame is swapped out of RAM the entry is initially changed to 'in transition'. It doesn't become 'invalid' unless the RAM backing it gets reused. Changing from 'in transition' back to 'valid' is apparently possible and a feature of the Windows VM. FWIW I haven't actually played with any of this myself. It's just an aspect of OS design that fascinates me so I've done a lot of research. 'Inside Windows NT' is a great source of information and a good read. It's by Helen Custer who also wrote 'Inside Windows NT File System'. My own experience of NTFS allows me to say that although she occasionally fudges the issue it's more a case of avoiding interminable detail rather than innaccuracy. ISBN:'Inside Windows NT':1-55615-481-X ISBN:'Inside Windows NT File System':1-55615-660-X Generally speaking I prefer the traditional 'swap out when you have to' strategy. ISTM that it allows a system to evolve into a stable, RAM-efficient configuration. In effect the VM adapts to the way the computer is being used and fully utilises RAM. Win2K is better than Win3 at least. Win3 seemed to like running with 50% of RAM unused which IMO was utter stupidity. Win2K seems more relaxed about things but I still think there's something wrong in using the swap file before RAM is exhausted. -- Andrue Cope [TeamB] [Bicester, Uk] http://info.borland.com/newsgroups/guide.html Back to top Nate Lockwood Guest Posted: Mon Sep 12, 2005 4:50 pm    Post subject: Re: Pagefile (swapfile) size Andrue Cope [TeamB] wrote: Quote: A page frame is zeroed before reuse (so as to adhere to the DoD C2 rules) but like most operations it is on-demand or 'lazy initialisation'. When a frame has been swapped out it remains in a 'Standby' state and can be reactivated. I guess that this would mean that availability of RAM wouldn't have to wait for transfer to disk in most cases and that would tend keep the execution speed high. I watched swap file usage by NIS when doing a Live Update. Norton insisted on updating my Parental Controls even though I don't use them. At the start the OS was using just over 256 MB of RAM and as the installation of the download progressed over 2 GB of swap file were used. It ramped up as a straight line and progress appeared to slow at the end. Now, unless the update was really, REALLY, compressed, it didn't appear to download anything like a couple of hundred MB of data so I don't know what it was doing - lots of recursive calls perhaps. It's lots faster with 1.5 GB of RAM compared to my old 1/4 GB, though, and the computer remains responsive. Thanks Nate Back to top Display posts from previous: All Posts1 Day7 Days2 Weeks1 Month3 Months6 Months1 Year Oldest FirstNewest First         BorlandTalk.com Forum Index -> C++ Builder (Non-Technical) All times are GMT Page 1 of 1   Jump to: Select a forum C++ Builder Newsgroups----------------C++ BuilderC++ Builder (ActiveX)C++ Builder (Announcements)C++ Builder (Command Line Tools)C++ Builder DatabasesC++ Builder Databases (ADO)C++ Builder Databases (Desktop)C++ Builder Databases (InterBase Express)C++ Builder Databases (Multi-Tier)C++ Builder Databases (SQL Servers)C++ Builder (Graphics)C++ Builder (IDE)C++ Builder (Internet)C++ Builder (Internet Socket)C++ Builder (Internet Web)C++ Builder (Jobs)C++ Builder (Language)C++ Builder (Language C++)C++ Builder (Compatibility with MFC)C++ Builder (Native API)C++ Builder (Non-Technical)C++ Builder (Students)C++ Builder (Third Party Tools)C++ Builder (Upgrade)C++ Builder (VCL)C++ Builder (VCL Components Usage)C++ Builder (VCL Components Development)C++ Builder (VCL Usage)C++ Builder (WinAPI)C++ Builder Installation Delphi Newsgroups----------------Delphi (General)Delphi ActiveX Controls UsageDelphi ActiveX Controls DevelopmentDelphi As400Delphi DatabasesDelphi Databases (ADO)Delphi Databases (dbExpress)Delphi Databases (Desktop)Delphi Databases (InterBase Express)Delphi Databases (Multi-Tier)Delphi Databases (SQL Servers)Delphi DeploymentDelphi GraphicsDelphi IDEDelphi InternationalizationDelphi InternetDelphi Internet Isapi-WebBrokerDelphi Internet WebSnapDelphi Internet WinsockDelphi JobsDelphi Language BASMDelphi Language ObjectPascalDelphi Model Driven Architecture (General)Delphi Model Driven Architecture (Third Party)Delphi MultimediaDelphi Native APIDelphi Non-TechnicalDelphi ObjectPascalDelphi OLE AutomationDelphi OO designDelphi OpenToolsAPIDelphi Reporting-ChartingDelphi RTLDelphi StudentsDelphi TeamSourceDelphi Thirdparty ToolsDelphi Thirdparty Tools (General)Delphi Thirdparty Tools (IntraWeb)Delphi Thirdparty Tools (RaveReports)Delphi UpgradeDelphi VCLDelphi VCL ComponentsDelphi VCL Components UsingDelphi VCL Components WritingDelphi WebServices SOAPDelphi WinAPIDelphi XMLDelphi Installationcomp.lang.pascal.delphi.components.misccomp.lang.pascal.delphi.components.usagecomp.lang.pascal.delphi.components.writingcomp.lang.pascal.delphi.databasescomp.lang.pascal.delphi.misccomp.sources.delphi JBuilder Newsgroups----------------JBuilderJBuilder AnnouncementsJBuilder Applet IssuesJBuilder As400JBuilder CompilerJBuilder CORBA/RMIJBuilder DatabasesJBuilder DB SwingJBuilder DebuggerJBuilder DeploymentJBuilder DocumentationJBuilder EnterpriseJBuilder HandheldJBuilder IDEJBuilder JavaJBuilder JavaAPIJBuilder Java LanguageJBuilder Java SwingJBuilder Java BeansJBuilder Java Beans UsageJBuilder Java Beans DevelopmentJBuilder JBCLJBuilder JDataStoreJBuilder JobsJBuilder LinuxJBuilder MacintoshJBuilder & MobileSetJBuilder MultiLingual AppsJBuilder Non-TechnicalJBuilder OpenToolsJBuilder Servlets (JSP)JBuilder StudentsJBuilder Team DevelopmentJBuilder Thirdparty ToolsJBuilder UpgradeJBuilder Installation InterBase Newsgroups----------------InterBaseInterBase Bug DiscussionInterBase GeneralInterBase IBConsoleInterBase OpenSourceInterBase ReplicationInterBase SQLInterBase ThirdpartyInterBase Installation Miscellaneous Borland Newsgroups----------------AppCenterAppServerEnteraVisiBroker  You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum Powered by phpBB © 2001, 2006 phpBB Group SEO toolkit © 2004-2006 webmedic.