enabling /largeaddressaware for cygwin in windows 7 64-bit

Corinna Vinschen corinna-cygwin@cygwin.com
Thu Aug 4 15:54:00 GMT 2011

On Aug  4 15:19, Amidon, William H. wrote:
> Hello,
> I am not a programming expert, and i wonder if you could give me some
> basic advice.
> I am running cygwin on a 64-bit Dell XPS, running Windows 7, with a
> Core i5 processor, and 12 GB of RAM installed.
> The fortran 90 code I am running keeps running out of memory (virtual
> memory or stack overflow errors) on jobs that the computer should

The main thread has a 2 Megs stack by default (Windows default).
If you're running out of stack space, there's not much we can do.
There's some way to define the default stacksize in the executable
header but off the top of my head I don't know how to change it.

> easily handle.  I have increased the paging memory to 36 MB, but I am
> afraid that CygWin is still being limited to ~ 1 GB of memory.

It's not.  It's limited to 2 Gigs usually, being a 32 bit DLL.  Only by
setting the large address awareness flag in the executable (not the
DLL!) you get a max of 4 Gigs of memory on 64 bit Windows.

> My problem is very similar to what is described here:
> http://cygwin.com/ml/cygwin/2011-01/msg00196.html
> I followed the instructions at [1] and [2] to increase the heap chunk

[2]?  That's not for 64 bit Windows.  If you tried that, take it back.

> available to cygwin, but I have also read that adding a
> /largeaddressaware link might further increase the amount of memory
> available to cygwin (see [3], which confused me a lot). 

If that confused you, you should probably not tamper with these
settings.  The maximum you should try is this:

- Revert the settings from [1].
- Download the latest Cygwin developer snapshot (only the DLL) from
- peflags --bigaddr=1 your_executable.exe

If that doesn't help, you're out of luck.


Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Project Co-Leader          cygwin AT cygwin DOT com
Red Hat

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