What I mean is will the memory be contiguous in fashion when it is resident.

AJ ONeal


On Mon, Aug 23, 2010 at 11:46 AM, Michael Torrie <[email protected]> wrote:

> On 08/23/2010 11:40 AM, AJ ONeal wrote:
> > Would it be true to say that if I allocate 120MB of memory with
> `malloc()`
> > that the physical memory underneath may actually be a block of 80MB and
> > 40MB?
>
> Not sure I understand your question.
>
> How much of the 120 MB of memory is resident (in physical memory)
> depends on the memory pressures and how the OS schedules things.  If you
> malloc the memory and do nothing with it, odds are zero bytes of the 120
> MB will be resident.
>
> > Now with a system with 4GB+ of memory, perhaps that's not very likely...
> but
> > it is possible, correct?
>
> Only if there's no swap enabled.  If swap is enabled, the kernel will
> likely swap out pages that aren't actually being actively used so that
> the physical RAM can be used for more useful things like disk caching.
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