Skip to main content

NS2 Installation in Ubuntu 22.04

Memory Management (Linux Kernel)


The data related to the processes are to be stored in the memory somehow by the operating system. In the olden days, primary memory is a scarce resource. and the application demands increases, so store the data of a process, it is necessary to use other forms of memory, either we can use

  • Physical address space
  • virtual address space
  1. Mapping the virtual addresses onto the physical addresses is the responsibility of the operating system’s memory management system.
  2. Memory protection prevents two processes exchanging data by changing the areas of memory used by both.
  3. The program code of a process can be executed in different threads at the same time. In principle, these threads share a common virtual address space.

Architecture Independent Memory Model

  1. Access time is the primary factor used in Physical (main) memory. To minimize the access times, the cache memory versions like Level1 Cache (L1 cache) and level2 cache (L2 Cache) were used.
  2. Cache memory improves the performance of Personal Computers.
  3. The physical memory is divided into pages (page memory) and the size is determined by the PAGE_SIZE macro of the asm/page.h file.
  4. For the x86 architecture, the page size is usually 4kbytes and 8kbytes for the 64 bit architecture and 64kbytes for the IA64 architecture
  5. The memory management units (MMU) of various architecture has the support the page size of 4Mbytes, which is necessary when the mapping between the physical address and virtual address takes place.

Virtual Address Space

  • The Code and the data of a process is scattered in the virtual address space.
  • the size of the Virtual address space depends on the number of bits used in the memory address, for example for a 32 bit memory address, nearly 4GBytes is available and for 64 bit memory address 16exabytes are available.
  • usually the process can be either in the user mode or system mode. Each process starts in the user mode initially and changed to system mode when there is a need to access the system resources.
  • The standard procedure to change from the user mode to the system mode is to call the software interrupt 0x80. In the user mode, access to kernel memory is forbidden. Access to the memory page can be granted to system mode or user mode.
  • The physical memory of the kernel maps to the virtual memory only after an offset (PAGE_OFFSET), but this memory space is permitted only under the system mode.
  • For this reason, the user address space is always smaller than the theoretical maximum. For example, for x86 – Page Size (4Kbytes) – User Address Space (3GB), but the theoretical maximum is 4GB.


Popular posts from this blog

Installation of NS2 (ns-2.35) in Ubuntu 20.04

Installation of NS2 (ns-2.35) in Ubuntu 20.04 LTS Step 1: Install the basic libraries like      $] sudo apt install build-essential autoconf automake libxmu-dev Step 2: install gcc-4.8 and g++-4.8 open the file using sudo mode $] sudo nano /etc/apt/sources.list Include the following line deb bionic main universe $] sudo apt update $] sudo apt install gcc-4.8 g++-4.8 Step 3:  Unzip the ns2 packages to home folder $] tar zxvf ns-allinone-2.35.tar.gz $] cd ns-allinone-2.35/ns-2.35 Modify the following make files. ~ns-2.35/ Change @CC@ to gcc-4.8 change @CXX@ to g++-4.8 ~nam-1.15/ ~xgraph-12.2/ ~otcl-1.14/ Change in all places  @CC@ to gcc-4.8 @CPP@ or @CXX@ to g++-4.8 open the file: ~ns-2.35/linkstate/ls.h Change at the Line no 137  void eraseAll() { erase(baseMap::begin(), baseMap::end()); } to This void eraseAll() { this->erase(baseMap::begin(), baseMap::end()); } All changes made Step 4: Open a new termi

Installing ns3 in Ubuntu 22.04 | Complete Instructions

In this post, we are going to see how to install ns-3.36.1 in Ubuntu 22.04. You can follow the video for complete details Tools used in this simulation: NS3 version ns-3.36.1  OS Used: Ubuntu 22.04 LTS Installation of NS3 (ns-3.36.1) There are some changes in the ns3 installation procedure and the dependencies. So open a terminal and issue the following commands Step 1:  Prerequisites $ sudo apt update In the following packages, all the required dependencies are taken care and you can install all these packages for the complete use of ns3. $ sudo apt install g++ python3 python3-dev pkg-config sqlite3 cmake python3-setuptools git qtbase5-dev qtchooser qt5-qmake qtbase5-dev-tools gir1.2-goocanvas-2.0 python3-gi python3-gi-cairo python3-pygraphviz gir1.2-gtk-3.0 ipython3 openmpi-bin openmpi-common openmpi-doc libopenmpi-dev autoconf cvs bzr unrar gsl-bin libgsl-dev libgslcblas0 wireshark tcpdump sqlite sqlite3 libsqlite3-dev  libxml2 libxml2-dev libc6-dev libc6-dev-i386 libclang-dev llvm-

VPL Jail Server Installation | Virtual Programming Laboratory with Moodle

Virtual Programming Laboratory (VPL)  This post tells you how to install VPL Jail Server Installation in Ubuntu 20.04 and how to configure it using Moodle Learning Management System. VPL - Virtual Programming Laboratory  For full installation with complete description, follow the video What is VPL? VPL is Virtual Programming Laboratory which is a tool for programming assignments, evaluation and running of programs. The programming languages supported by VPL is C, C++, Java, Python, Perl, PHP, NodeJS, Verilog, etc. Step 1 - Install  VPN Jail Server Installation  My Server configuration  16GB RAM and 16 Core PRocessor (Intel Xeon)  Virtual Machine  Ubuntu 20.04 (64 bit OS). To download the softwares  Unzip or untar the above file in the home folder (in my case it is /home/tspradeepkumar/ ) $ cd vpl-jail-system-2.7.2/ $ sudo ./install-vpl-sh VPL Jail Server Installation This will take some time based on your internet connection: To Star