mmap caching

[Laszlo Nagy]

> In fact, memory that is read in because of mmap should *never* cause
> a MemoryError. 
This is certainly not true. You can run out of virtual address space by 
reading data from a memory mapped file.
> Python calls MapViewOfFile when mmap.mmap is invoked,
> at which point the operating commits to providing that much address
> space to the application, along with backing storage on disk
> (typically, from the file being mapped, unless it is an anonymous
> map). Later access to the mapped range cannot fail (except for
> hardware errors), and if it would, you wouldn't see a MemoryError.
>   
Hmm, maybe I'm wrong. Are you sure that Windows allocates the size of 
the whole file in terms of memory address space? I also wrote a program 
before (in Delphi). That program was playing a memory mapped wave file. 
 From the task manager, I have seen that "used memory" was growing as 
the program was playing the wave file. For me, this indicates that 
Windows extends the mapped address space in chunks.

Regards,

   Laszlo