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Huge Pages:

Huge pages allow for mapping of contiguous pages in kernel.
To see how to enable it on debian, see https://wiki.debian.org/Hugepages#pages-size

Following are the steps I took for allocating 2 chunks, each of 1 GB on my system:

1) Run command 'grep pdpe1gb /proc/cpuinfo | uniq'
If this command output is not empty, the x86 system supports 1GB hugepages.

2) Edit /etc/default/grub to add "hugepagesz=1GB hugepages=2 default_hugepagesz=1GB"
as boot params.
This allows kernel to reserve the memory during system boot.

3) Run command 'update-grub2'
This updates grub so that kernel get the new boot commands.

4) Reboot system

5) Run 'cat /proc/meminfo | grep "Hugepagesize:"'
The output should be 1048576 kB. This means now the default Hugepage is set to 1GB

6) Run 'cat /proc/meminfo | grep "HugePages_Free:"'
The output should be 2. This shows 2 chunks of 2 GB has been reserved.

7) Now your application can mmap() using MAP_HUGETLB. 1GB chunks will be used 
as it is set as the default huge page size.