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I would like to write a program to consume all the memory available to understand the outcome. I've heard that linux starts killing the processes once it is unable to allocate the memory.
Can anyone help me with such a program.
I have written the following, but the memory doesn't seem to get exhausted:
#include <stdlib.h> int main() { while(1) { malloc(1024*1024); } return 0; } 
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To simply exhaust memory, you don't need that at all. You can call new int(i) and throw away the returned pointer, and the memory will still be allocated. Remember also that your machine likely has virtual memory beyond the 2 GB physical RAM you have installed.
In C, dynamic memory is allocated from the heap using some standard library functions. The two key dynamic memory functions are malloc() and free(). The malloc() function takes a single parameter, which is the size of the requested memory area in bytes. It returns a pointer to the allocated memory.
You should write to the allocated blocks. If you just ask for memory, linux might just hand out a reservation for memory, but nothing will be allocated until the memory is accessed.
int main() { while(1) { void *m = malloc(1024*1024); memset(m,0,1024*1024); } return 0; } You really only need to write 1 byte on every page (4096 bytes on x86 normally) though.
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Linux "over commits" memory. This means that physical memory is only given to a process when the process first tries to access it, not when the malloc is first executed. To disable this behavior, do the following (as root):
echo 2 > /proc/sys/vm/overcommit_memory Then try running your program.
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