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SubjectRe: address space reservation functionality?
Arjan van de Ven wrote:
> On Mon, 2005-01-10 at 15:52 -0500, Robert W. Fuller wrote:
>
>>Hi,
>>
>>I was wondering if some functionality existed in Linux. Specifically,
>>in Solaris, you can mmap the null device in order to reserve part of the
>>address space without otherwise consuming resources. This is detailed
>>in the Solaris manpage null(7D). The same functionality is also
>>available under Windows NT/XP/2K by calling the VirtualAlloc function
>>with the MEM_RESERVE flag omitting the MEM_COMMIT flag. Does Linux have
>>a similar mechanism buried somewhere whereby I can reserve a part of the
>>address space and not increase the "virtual size" of the process or the
>>system's idea of the amount of memory in use? I could not find one by
>>using the source.
>
>
> malloc() already does this...
> what you describe is the default behavior of linux; only when you
> actually write to the memory does it get backed by ram.
>
>

Sorry about the top posting. This is a resend without it.

This is not quite the same thing. This still does a check for whether
or not there is enough memory and includes this in the virtual size of
the process. I simply want to reserve a part of the address space so
I'm guaranteed I can map something else over a contiguous portion of the
address space. I don't want it to check for available memory or
increase the virtual size of the process because I will be using this
region sparsely. That is why Solaris and Windows have separate
interfaces for this.
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