Can some throw bright light on Linux Memory Allocation

[MirJafar Aki]

Hello,

I have installed Ubuntu on a machine with following
config.

RAM :  2 GB
Machine:  Intel Core 2 Duo
OS:  Ubuntu 64 bit.
Disk:  250 GB.


I have attached a simple program to test memory allocation on linux and
something strange is happening.

1.    If I invoke large_memory function then maximum
       size I am allowed is 245GB.

2.    If I use less than 245GB  ( say 244 GB) then the
       second stage is also passed.  Where from OS is
       allocating 244GB ?

3.   Strange enough, if I use chuck memory, I can
      goto 3817GB before I get segmentation fault.
      ( and buf == NULL is never reached ).

4.   Much more strange, GoogleHeapProfiler, and
      ValGrindHeap profile also add to my uneasiness
      and report that 3817GB allocation is successful.

What is happening ? Please help.

Mir
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