Pharaoh . wrote:
Afaik, for a 32 - bit machine we can not address more than 2^32
addresses. Now, If I
have another machine with 1 GB RAM and 4 GB swap then, as per above
inference I
should be able to allocated 5 GB memory at max ! Out of this only lower
4 GB will be
addressable.
Is there some loophole in the above argument?
On a 32 bit x86 system, there is 3GB of virtual address space
available for user space. All allocations, including the mapping
of the executable, shared libraries, the stack, etc. need to fit
inside that.
Address randomization (a security method) eats up some address
space.
This limits the maximum amount of memory allocated my malloc to
the remaining 2.8 or so GB.
The reason you cannot "allocate more than you can address" is
that malloc returns a virtual address. Once virtual memory
fills up, there's no other place to map the memory.
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