Java maximum memory on Windows XP

Question

I ve always been able to allocate 1400 megabytes for Java SE running on 32-bit Windows XP  Java 1 4  1 5 and 1 6    java -Xmx1400m       Today I tried the same option on a new Windows XP machine using Java 1 5 16 and 1 6 0 07 and got the error   Error occurred during initialization of VM Could not reserve enough space for object heap Could not create the Java virtual machine    Through trial and error it seems 1200 megabytes is the most I can allocate on this machine   Any ideas why one machine would allow 1400 and another only 1200   Edit  The machine has 4GB of RAM with about 3 5GB that Windows can recognize

User · Answer

Oracle JRockit  which can handle a non-contiguous heap  can have a Java heap size of 2 85 GB on Windows 2003 XP with the  3GB switch  It seems that fragmentation can have quite an impact on how large a Java heap can be

User · Answer

This has to do with contiguous memory   Here s some info I found online for somebody asking that before  supposedly from a  VM god       The reason we need a contiguous memory   region for the heap is that we have a   bunch of side data structures that are   indexed by  scaled  offsets from the   start of the heap  For example  we   track object reference updates with a    card mark array  that has one byte   for each 512 bytes of heap  When we   store a reference in the heap we have   to mark the corresponding byte in the   card mark array  We right shift the   destination address of the store and   use that to index the card mark array    Fun addressing arithmetic games you   can t do in Java that you get to  have   to  -  play in C         Usually we don t have trouble getting   modest contiguous regions  up to about   1 5GB on Windohs  up to about 3 8GB on Solaris  YMMV    On Windohs  the   problem is mostly that there are some   libraries that get loaded before the   JVM starts up that break up the   address space  Using the  3GB switch   won t rebase those libraries  so they   are still a problem for us       We know how to make chunked heaps  but   there would be some overhead to using   them  We have more requests for faster   storage management than we do for   larger heaps in the 32-bit JVM  If you   really want large heaps  switch to the   64-bit JVM  We still need contiguous   memory  but it s much easier to get in   a 64-bit address space

User · Answer

The JVM needs contiguous memory and depending on what else is running  what was running before  and how windows has managed memory you may be able to get up to 1 4GB of contiguous memory   I think 64bit Windows will allow larger heaps

User · Answer

There are numerous ways to change heap size like    file- setting- build  exceution  deployment- compiler  here you will find heap size file- setting- build  exceution  deployment- compiler- andriod here also you will find heap size  You can refer this for andriod project if you facing same issue    What worked for me was    Set proper appropriate JAVA HOME path incase you java got updated  create new system variable computer- properties- advanced setting- create new system variable   name   JAVA OPTION value  -Xmx750m  FYI   you can find default VMoption in Intellij help- edit custom VM option   In this file you see min and max size of heap

User · Answer

This has to do with contiguous memory   Here s some info I found online for somebody asking that before  supposedly from a  VM god       The reason we need a contiguous memory   region for the heap is that we have a   bunch of side data structures that are   indexed by  scaled  offsets from the   start of the heap  For example  we   track object reference updates with a    card mark array  that has one byte   for each 512 bytes of heap  When we   store a reference in the heap we have   to mark the corresponding byte in the   card mark array  We right shift the   destination address of the store and   use that to index the card mark array    Fun addressing arithmetic games you   can t do in Java that you get to  have   to  -  play in C         Usually we don t have trouble getting   modest contiguous regions  up to about   1 5GB on Windohs  up to about 3 8GB on Solaris  YMMV    On Windohs  the   problem is mostly that there are some   libraries that get loaded before the   JVM starts up that break up the   address space  Using the  3GB switch   won t rebase those libraries  so they   are still a problem for us       We know how to make chunked heaps  but   there would be some overhead to using   them  We have more requests for faster   storage management than we do for   larger heaps in the 32-bit JVM  If you   really want large heaps  switch to the   64-bit JVM  We still need contiguous   memory  but it s much easier to get in   a 64-bit address space

User · Answer

I think it has more to do with how Windows is configured as hinted by this response  Java -Xmx Option  Some more testing  I was able to allocate 1300MB on an old Windows XP machine with only 768MB physical RAM  plus virtual memory   On my 2GB RAM machine I can only get 1220MB  On various other corporate machines  with older Windows XP  I was able to get 1400MB  The machine with a 1220MB limit is pretty new  just purchased from Dell   so maybe it has newer  and more bloated  Windows and DLLs  it s running Window XP Pro Version 2002 SP2

User · Answer

Keep in mind that Windows has virtual memory management and the JVM only needs memory that is contiguous in its address space  So  other programs running on the system shouldn t necessarily impact your heap size  What will get in your way are DLL s that get loaded in to your address space  Unfortunately optimizations in Windows that minimize the relocation of DLL s during linking make it more likely you ll have a fragmented address space  Things that are likely to cut in to your address space aside from the usual stuff include security software  CBT software  spyware and other forms of malware  Likely causes of the variances are different security patches  C runtime versions  etc  Device drivers and other kernel bits have their own address space  the other 2GB of the 4GB 32-bit space    You could try going through your DLL bindings in your JVM process and look at trying to rebase your DLL s in to a more compact address space  Not fun  but if you are desperate     Alternatively  you can just switch to 64-bit Windows and a 64-bit JVM  Despite what others have suggested  while it will chew up more RAM  you will have much more contiguous virtual address space  and allocating 2GB contiguously would be trivial

User · Answer

I got this error message when running a java program from a  limited memory  virtuozzo VPS  I had not specified any memory arguments  and found I had to explicitly set a small amount as the default must have been too high  E g  -Xmx32m  obviously needs to be tuned depending on the program you run    Just putting this here in case anyone else gets the above error message without specifying a large amount of memory like the questioner did

User · Answer

The Java heap size limits for Windows are    maximum possible heap size on 32-bit Java  1 8 GB recommended heap size limit on 32-bit Java  1 5 GB  or 1 8 GB with  3GB option    This doesn t help you getting a bigger Java heap  but now you know you can t go beyond these values

User · Answer

First  using a page-file when you have 4 GB of RAM is useless  Windows can t access more than 4GB  actually  less because of memory holes  so the page file is not used   Second  the address space is split in 2  half for kernel  half for user mode  If you need more RAM for your applications use the  3GB option in boot ini  make sure java exe is marked as  large address aware   google for more info    Third  I think you can t allocate the full 2 GB of address space because java wastes some memory internally  for threads  JIT compiler  VM initialization  etc   Use the  3GB switch for more

User · Answer

sun s JDK JRE needs a contiguous amount of memory if you allocate a huge block   The OS and initial apps tend to allocate bits and pieces during loading which fragments the available RAM  If a contiguous block is NOT available  the SUN JDK cannot use it  JRockit from Bea acquired by Oracle  can allocate memory from pieces

User · Answer

Everyone seems to be answering about contiguous memory  but have neglected to acknowledge a more pressing issue   Even with 100  contiguous memory allocation  you can t have a 2 GiB heap size on a 32-bit Windows OS   by default   This is because 32-bit Windows processes cannot address more than 2 GiB of space   The Java process will contain perm gen  pre Java 8   stack size per thread  JVM   library overhead  which pretty much increases with each build  all in addition to the heap   Furthermore  JVM flags and their default values change between versions  Just run the following and you ll get some idea    java -XX  PrintFlagsFinal   Lots of the options affect memory division in and out of the heap  Leaving you with more or less of that 2 GiB to play with     To reuse portions of this answer of mine  about Tomcat  but applies to any Java process       The Windows OS   limits the memory allocation of a 32-bit process to 2 GiB in total  by   default         You will only be able  to allocate around 1 5 GiB heap   space because there is also other memory allocated to the process    the JVM   library overhead  perm gen space etc         Why does 32-bit Windows impose a 2 GB process address space limit  but   64-bit Windows impose a 4GB limit       Other modern operating systems  cough Linux  allow 32-bit processes to   use all  or most  of the 4 GiB addressable space       That said  64-bit Windows OS s can be configured to increase the limit   of 32-bit processes to 4 GiB  3 GiB on 32-bit        http   msdn microsoft com en-us library windows desktop aa366778 v vs 85  aspx

User · Answer

Keep in mind that Windows has virtual memory management and the JVM only needs memory that is contiguous in its address space  So  other programs running on the system shouldn t necessarily impact your heap size  What will get in your way are DLL s that get loaded in to your address space  Unfortunately optimizations in Windows that minimize the relocation of DLL s during linking make it more likely you ll have a fragmented address space  Things that are likely to cut in to your address space aside from the usual stuff include security software  CBT software  spyware and other forms of malware  Likely causes of the variances are different security patches  C runtime versions  etc  Device drivers and other kernel bits have their own address space  the other 2GB of the 4GB 32-bit space    You could try going through your DLL bindings in your JVM process and look at trying to rebase your DLL s in to a more compact address space  Not fun  but if you are desperate     Alternatively  you can just switch to 64-bit Windows and a 64-bit JVM  Despite what others have suggested  while it will chew up more RAM  you will have much more contiguous virtual address space  and allocating 2GB contiguously would be trivial

User · Answer

sun s JDK JRE needs a contiguous amount of memory if you allocate a huge block   The OS and initial apps tend to allocate bits and pieces during loading which fragments the available RAM  If a contiguous block is NOT available  the SUN JDK cannot use it  JRockit from Bea acquired by Oracle  can allocate memory from pieces

User · Answer

First  using a page-file when you have 4 GB of RAM is useless  Windows can t access more than 4GB  actually  less because of memory holes  so the page file is not used   Second  the address space is split in 2  half for kernel  half for user mode  If you need more RAM for your applications use the  3GB option in boot ini  make sure java exe is marked as  large address aware   google for more info    Third  I think you can t allocate the full 2 GB of address space because java wastes some memory internally  for threads  JIT compiler  VM initialization  etc   Use the  3GB switch for more

User · Answer

There are numerous ways to change heap size like    file- setting- build  exceution  deployment- compiler  here you will find heap size file- setting- build  exceution  deployment- compiler- andriod here also you will find heap size  You can refer this for andriod project if you facing same issue    What worked for me was    Set proper appropriate JAVA HOME path incase you java got updated  create new system variable computer- properties- advanced setting- create new system variable   name   JAVA OPTION value  -Xmx750m  FYI   you can find default VMoption in Intellij help- edit custom VM option   In this file you see min and max size of heap

User · Answer

I think it has more to do with how Windows is configured as hinted by this response  Java -Xmx Option  Some more testing  I was able to allocate 1300MB on an old Windows XP machine with only 768MB physical RAM  plus virtual memory   On my 2GB RAM machine I can only get 1220MB  On various other corporate machines  with older Windows XP  I was able to get 1400MB  The machine with a 1220MB limit is pretty new  just purchased from Dell   so maybe it has newer  and more bloated  Windows and DLLs  it s running Window XP Pro Version 2002 SP2

User · Answer

sun s JDK JRE needs a contiguous amount of memory if you allocate a huge block   The OS and initial apps tend to allocate bits and pieces during loading which fragments the available RAM  If a contiguous block is NOT available  the SUN JDK cannot use it  JRockit from Bea acquired by Oracle  can allocate memory from pieces

User · Answer

Sun s JVM needs contiguous memory  So the maximal amount of available memory is dictated by memory fragmentation  Especially driver s dlls tend to fragment the memory  when loading into some predefined base address  So your hardware and its drivers determine how much memory you can get    Two sources for this with statements from Sun engineers  forum blog  Maybe another JVM  Have you tried Harmony  I think they planned to allow non-continuous memory

User · Answer

Oracle JRockit  which can handle a non-contiguous heap  can have a Java heap size of 2 85 GB on Windows 2003 XP with the  3GB switch  It seems that fragmentation can have quite an impact on how large a Java heap can be

User · Answer

The Java heap size limits for Windows are    maximum possible heap size on 32-bit Java  1 8 GB recommended heap size limit on 32-bit Java  1 5 GB  or 1 8 GB with  3GB option    This doesn t help you getting a bigger Java heap  but now you know you can t go beyond these values

User · Answer

Oracle JRockit  which can handle a non-contiguous heap  can have a Java heap size of 2 85 GB on Windows 2003 XP with the  3GB switch  It seems that fragmentation can have quite an impact on how large a Java heap can be

User · Answer

Keep in mind that Windows has virtual memory management and the JVM only needs memory that is contiguous in its address space  So  other programs running on the system shouldn t necessarily impact your heap size  What will get in your way are DLL s that get loaded in to your address space  Unfortunately optimizations in Windows that minimize the relocation of DLL s during linking make it more likely you ll have a fragmented address space  Things that are likely to cut in to your address space aside from the usual stuff include security software  CBT software  spyware and other forms of malware  Likely causes of the variances are different security patches  C runtime versions  etc  Device drivers and other kernel bits have their own address space  the other 2GB of the 4GB 32-bit space    You could try going through your DLL bindings in your JVM process and look at trying to rebase your DLL s in to a more compact address space  Not fun  but if you are desperate     Alternatively  you can just switch to 64-bit Windows and a 64-bit JVM  Despite what others have suggested  while it will chew up more RAM  you will have much more contiguous virtual address space  and allocating 2GB contiguously would be trivial

User · Answer

I think it has more to do with how Windows is configured as hinted by this response  Java -Xmx Option  Some more testing  I was able to allocate 1300MB on an old Windows XP machine with only 768MB physical RAM  plus virtual memory   On my 2GB RAM machine I can only get 1220MB  On various other corporate machines  with older Windows XP  I was able to get 1400MB  The machine with a 1220MB limit is pretty new  just purchased from Dell   so maybe it has newer  and more bloated  Windows and DLLs  it s running Window XP Pro Version 2002 SP2

User · Answer

The JVM needs contiguous memory and depending on what else is running  what was running before  and how windows has managed memory you may be able to get up to 1 4GB of contiguous memory   I think 64bit Windows will allow larger heaps

User · Answer

Sun s JVM needs contiguous memory  So the maximal amount of available memory is dictated by memory fragmentation  Especially driver s dlls tend to fragment the memory  when loading into some predefined base address  So your hardware and its drivers determine how much memory you can get    Two sources for this with statements from Sun engineers  forum blog  Maybe another JVM  Have you tried Harmony  I think they planned to allow non-continuous memory

User · Answer

First  using a page-file when you have 4 GB of RAM is useless  Windows can t access more than 4GB  actually  less because of memory holes  so the page file is not used   Second  the address space is split in 2  half for kernel  half for user mode  If you need more RAM for your applications use the  3GB option in boot ini  make sure java exe is marked as  large address aware   google for more info    Third  I think you can t allocate the full 2 GB of address space because java wastes some memory internally  for threads  JIT compiler  VM initialization  etc   Use the  3GB switch for more

User · Answer

First  using a page-file when you have 4 GB of RAM is useless  Windows can t access more than 4GB  actually  less because of memory holes  so the page file is not used   Second  the address space is split in 2  half for kernel  half for user mode  If you need more RAM for your applications use the  3GB option in boot ini  make sure java exe is marked as  large address aware   google for more info    Third  I think you can t allocate the full 2 GB of address space because java wastes some memory internally  for threads  JIT compiler  VM initialization  etc   Use the  3GB switch for more

User · Answer

The Java heap size limits for Windows are    maximum possible heap size on 32-bit Java  1 8 GB recommended heap size limit on 32-bit Java  1 5 GB  or 1 8 GB with  3GB option    This doesn t help you getting a bigger Java heap  but now you know you can t go beyond these values

User · Answer

Keep in mind that Windows has virtual memory management and the JVM only needs memory that is contiguous in its address space  So  other programs running on the system shouldn t necessarily impact your heap size  What will get in your way are DLL s that get loaded in to your address space  Unfortunately optimizations in Windows that minimize the relocation of DLL s during linking make it more likely you ll have a fragmented address space  Things that are likely to cut in to your address space aside from the usual stuff include security software  CBT software  spyware and other forms of malware  Likely causes of the variances are different security patches  C runtime versions  etc  Device drivers and other kernel bits have their own address space  the other 2GB of the 4GB 32-bit space    You could try going through your DLL bindings in your JVM process and look at trying to rebase your DLL s in to a more compact address space  Not fun  but if you are desperate     Alternatively  you can just switch to 64-bit Windows and a 64-bit JVM  Despite what others have suggested  while it will chew up more RAM  you will have much more contiguous virtual address space  and allocating 2GB contiguously would be trivial

User · Answer

The JVM needs contiguous memory and depending on what else is running  what was running before  and how windows has managed memory you may be able to get up to 1 4GB of contiguous memory   I think 64bit Windows will allow larger heaps

User · Answer

Sun s JVM needs contiguous memory  So the maximal amount of available memory is dictated by memory fragmentation  Especially driver s dlls tend to fragment the memory  when loading into some predefined base address  So your hardware and its drivers determine how much memory you can get    Two sources for this with statements from Sun engineers  forum blog  Maybe another JVM  Have you tried Harmony  I think they planned to allow non-continuous memory

User · Answer

Everyone seems to be answering about contiguous memory  but have neglected to acknowledge a more pressing issue   Even with 100  contiguous memory allocation  you can t have a 2 GiB heap size on a 32-bit Windows OS   by default   This is because 32-bit Windows processes cannot address more than 2 GiB of space   The Java process will contain perm gen  pre Java 8   stack size per thread  JVM   library overhead  which pretty much increases with each build  all in addition to the heap   Furthermore  JVM flags and their default values change between versions  Just run the following and you ll get some idea    java -XX  PrintFlagsFinal   Lots of the options affect memory division in and out of the heap  Leaving you with more or less of that 2 GiB to play with     To reuse portions of this answer of mine  about Tomcat  but applies to any Java process       The Windows OS   limits the memory allocation of a 32-bit process to 2 GiB in total  by   default         You will only be able  to allocate around 1 5 GiB heap   space because there is also other memory allocated to the process    the JVM   library overhead  perm gen space etc         Why does 32-bit Windows impose a 2 GB process address space limit  but   64-bit Windows impose a 4GB limit       Other modern operating systems  cough Linux  allow 32-bit processes to   use all  or most  of the 4 GiB addressable space       That said  64-bit Windows OS s can be configured to increase the limit   of 32-bit processes to 4 GiB  3 GiB on 32-bit        http   msdn microsoft com en-us library windows desktop aa366778 v vs 85  aspx

User · Answer

Here is how to increase the Paging size   right click on mycomputer--- properties--- Advanced  in the performance section click settings  click Advanced tab  in Virtual memory section  click change  It will show ur current paging  size   Select Drive where HDD space is available   Provide initial size and max size    e g  initial size 0 MB and max size  4000 MB   As much as you will require

User · Answer

I got this error message when running a java program from a  limited memory  virtuozzo VPS  I had not specified any memory arguments  and found I had to explicitly set a small amount as the default must have been too high  E g  -Xmx32m  obviously needs to be tuned depending on the program you run    Just putting this here in case anyone else gets the above error message without specifying a large amount of memory like the questioner did

User · Answer

Sun s JVM needs contiguous memory  So the maximal amount of available memory is dictated by memory fragmentation  Especially driver s dlls tend to fragment the memory  when loading into some predefined base address  So your hardware and its drivers determine how much memory you can get    Two sources for this with statements from Sun engineers  forum blog  Maybe another JVM  Have you tried Harmony  I think they planned to allow non-continuous memory

User · Answer

I think it has more to do with how Windows is configured as hinted by this response  Java -Xmx Option  Some more testing  I was able to allocate 1300MB on an old Windows XP machine with only 768MB physical RAM  plus virtual memory   On my 2GB RAM machine I can only get 1220MB  On various other corporate machines  with older Windows XP  I was able to get 1400MB  The machine with a 1220MB limit is pretty new  just purchased from Dell   so maybe it has newer  and more bloated  Windows and DLLs  it s running Window XP Pro Version 2002 SP2

User · Answer

The JVM needs contiguous memory and depending on what else is running  what was running before  and how windows has managed memory you may be able to get up to 1 4GB of contiguous memory   I think 64bit Windows will allow larger heaps

User · Answer

Oracle JRockit  which can handle a non-contiguous heap  can have a Java heap size of 2 85 GB on Windows 2003 XP with the  3GB switch  It seems that fragmentation can have quite an impact on how large a Java heap can be

User · Answer

sun s JDK JRE needs a contiguous amount of memory if you allocate a huge block   The OS and initial apps tend to allocate bits and pieces during loading which fragments the available RAM  If a contiguous block is NOT available  the SUN JDK cannot use it  JRockit from Bea acquired by Oracle  can allocate memory from pieces

User · Answer

This has to do with contiguous memory   Here s some info I found online for somebody asking that before  supposedly from a  VM god       The reason we need a contiguous memory   region for the heap is that we have a   bunch of side data structures that are   indexed by  scaled  offsets from the   start of the heap  For example  we   track object reference updates with a    card mark array  that has one byte   for each 512 bytes of heap  When we   store a reference in the heap we have   to mark the corresponding byte in the   card mark array  We right shift the   destination address of the store and   use that to index the card mark array    Fun addressing arithmetic games you   can t do in Java that you get to  have   to  -  play in C         Usually we don t have trouble getting   modest contiguous regions  up to about   1 5GB on Windohs  up to about 3 8GB on Solaris  YMMV    On Windohs  the   problem is mostly that there are some   libraries that get loaded before the   JVM starts up that break up the   address space  Using the  3GB switch   won t rebase those libraries  so they   are still a problem for us       We know how to make chunked heaps  but   there would be some overhead to using   them  We have more requests for faster   storage management than we do for   larger heaps in the 32-bit JVM  If you   really want large heaps  switch to the   64-bit JVM  We still need contiguous   memory  but it s much easier to get in   a 64-bit address space

User · Answer

Here is how to increase the Paging size   right click on mycomputer--- properties--- Advanced  in the performance section click settings  click Advanced tab  in Virtual memory section  click change  It will show ur current paging  size   Select Drive where HDD space is available   Provide initial size and max size    e g  initial size 0 MB and max size  4000 MB   As much as you will require

User · Answer

The Java heap size limits for Windows are    maximum possible heap size on 32-bit Java  1 8 GB recommended heap size limit on 32-bit Java  1 5 GB  or 1 8 GB with  3GB option    This doesn t help you getting a bigger Java heap  but now you know you can t go beyond these values

User · Answer

This has to do with contiguous memory   Here s some info I found online for somebody asking that before  supposedly from a  VM god       The reason we need a contiguous memory   region for the heap is that we have a   bunch of side data structures that are   indexed by  scaled  offsets from the   start of the heap  For example  we   track object reference updates with a    card mark array  that has one byte   for each 512 bytes of heap  When we   store a reference in the heap we have   to mark the corresponding byte in the   card mark array  We right shift the   destination address of the store and   use that to index the card mark array    Fun addressing arithmetic games you   can t do in Java that you get to  have   to  -  play in C         Usually we don t have trouble getting   modest contiguous regions  up to about   1 5GB on Windohs  up to about 3 8GB on Solaris  YMMV    On Windohs  the   problem is mostly that there are some   libraries that get loaded before the   JVM starts up that break up the   address space  Using the  3GB switch   won t rebase those libraries  so they   are still a problem for us       We know how to make chunked heaps  but   there would be some overhead to using   them  We have more requests for faster   storage management than we do for   larger heaps in the 32-bit JVM  If you   really want large heaps  switch to the   64-bit JVM  We still need contiguous   memory  but it s much easier to get in   a 64-bit address space

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