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Java Forum / General / June 2007Page file and memory in Java
Hi, I have to allocate a large amount of memory in java appl., but I noticed that operating system (windows xp) move large parts of heap from ram to page file. Does anybody know how can I avoid paging in java? Thanks in advance > Hi, > [quoted text clipped - 4 lines] > > Thanks in advance Java doesn't do the paging; the underlying OS handles that.  SignatureSteve W. Jackson Montgomery, Alabama > I have to allocate a large amount of memory in java appl., but I noticed > that operating system (windows xp) move large parts of heap from ram to > page file. > Does anybody know how can I avoid paging in java? Java allocates virtual memory from the OS. The OS back that virtual memory with physical memory and page file. It is not a Java problem. It is an operating system problem. I don't think WinXP really limits a processes RAM usage, so maybe there are two many and too big processes for the available RAM ? Arne > Java allocates virtual memory from the OS. The OS back > that virtual memory with physical memory and page file. [quoted text clipped - 7 lines] > > Arne I know, but I hoped that there was some 'magic' option of JVM which forbids WinXP to move ram to page file. > I know, but I hoped that there was some 'magic' option of JVM which > forbids WinXP to move ram [sic] to page file. There is - run it in Linux or add more RAM or stop running the other programs on the same box. OK, only the first option actually forbids Win XP to swap the JVM's RAM. The others can help, though. SignatureLew >> I know, but I hoped that there was some 'magic' option of JVM which >> forbids WinXP to move ram [sic] to page file. [quoted text clipped - 4 lines] > OK, only the first option actually forbids Win XP to swap the JVM's > RAM. The others can help, though. I think there is some magic you can do - but note that it will not be portable to other OSs. Take a look at the KeepResident plugin for eclipse: http://suif.stanford.edu/pub/keepresident/ This shows you how to do it. Windows is over-zealous about paging out because it thinks its better to keep memory for disk buffer cache than for your large (in Windows terms) badly behaved JVM....... Dave >>> I know, but I hoped that there was some 'magic' option of JVM which >>> forbids WinXP to move ram [sic] to page file. [quoted text clipped - 19 lines] > > Dave If you have sufficient physical memory (2GB or more) you could just disable paging at the OS level. I routinely run my 2GB desktop and laptop with paging turned off (paging file size == 0). > If you have sufficient physical memory (2GB or more) you could > just disable paging at the OS level. I routinely run my 2GB > desktop and laptop with paging turned off (paging file size == 0). I do the same thing. Even though I never exhaust physical RAM, I've noticed that disabling the page file on Windows results in a huge performance increase. Linux doesn't seem to have this problem. >> If you have sufficient physical memory (2GB or more) you could >> just disable paging at the OS level. I routinely run my 2GB [quoted text clipped - 6 lines] > > Linux doesn't seem to have this problem. As someone else said, Windows is very aggressive about swapping out application code in favor of I/O buffers, while Linux uses a more sane approach. In linux you can actually control the 'swappiness' of the system as a whole (but I can't remember the parameter right now). Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. Simply choose a title, complete the application form and submit it. Read more ...
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