This report enhances
the proposal, operation, and likely projects of Linux. In Real-Time Linux, a
typical time-sharing Operating System and a real-time decision-making route on
the parallel system. ICE (Interrupt controller emulation) is castoff to
assurance a truncated determined interrupt potential individualistically of the
base system. Existence of a one-shot timer makes it happen to accomplish a
truncated task statement jitter deprived of negotiating production. Lock-free
FIFO buers are working for communicating among real-time tasks and Linux
processes. User-dened schedulers are permissible as are run-time variations in
the scheduling strategy.
Table of Contents:
History of Linux
In 1970, it is introduced by Bell Labs.
Linux is an efficient kind of Unix. It is a very popular Real-Time
Operating system. It is easy to available and free to use system. It is familiar
to Unix. Linux is a multi-user atmosphere which delivers cost-effective access.
It can run multiple applications at similar time. It supports hierarchal file
Components of Linux:
Some basic components of Linux are:
All most important activities of system
are done by Kernel.
It contains extraordinary functions to
access Kernel’s features
It is responsible for specialized level jobs.
Architecture of Real-Time Linux Operating
Following are the layers on which the
architecture of Linux stands:
devices like RAM, HDD, CUP etc makes up the hardware layer.
Kernel is supposed to be the most important
component of Linux, it communicates directly to Operating systems, and serves
services to high layer components from low level components.
Shell hides from user,
the complexity of functions of kernel, it is basically an interface. It
executes functions of kernel by taking commands as an input from users.
Most of the
functionalities of operating systems are provided by utility programs.
Linux stands on some basic principles for
RAM: an unused RAM of page is garbage RAM. RAM stores data on disk for fastest
access and store for kernel. It is not only the user application data. Storage
of such data in RAM is refer as buffer, cache, disk cache. Cache is free
memory, it can easily and rapidly be substituted by any program that is on
running or just starting who wants memory.
Cache is essential in several means, it helps
reducing processing, recently processed page can easily be load in some little
time interval as it remains in Cache memory.
Free command in system is the command who
gives initial idea of how your RAM is to be used.
The physical address is provided by map.
Physical address is divided into frames which are
equivalent to 4KBS each.
Physical memory can never be allocated directly by the
system. It needs virtual memory and the virtual memory uses page for mapping
User and Kernal Address Space:
In many systems Linux Page Cache is the only main user of
RAM. The read() function is used to read data from file of disk and transfer it
to page cache. Kernel has privilege to discard the page after the read(), if
the page is not used. If you want to read same file the next time, you do not
need to process it again. It will show up directly on the next read. This is
the reason Linux page use the cache mostly, as it reduced the processing to
access the page again.
When no space is left in RAM and application
needs more space. It start swapping less occupied portion of pages for space.
The infrequently used pages of application are being under attack for this purpose.
For more memory information:
Scheduling in Linux:
Scheduling is basically done in a way the user is not
known when the source code is stop executing and paused for some time interval to give privileges
to another user to execute the source code.
The objectives on which scheduling processes are stand is
when to switch and what process to be selected are:
The response time should be quick
The process starvation must be evaded.
For backend jobs the good output is required.
Soft real time process must be maintained.
As per Priority policies, the high priority program
paused the low priority program and executes itself first; in short low
priority program is preempted by high priority program.
View of Kernel Scheduler:
This is how the kernel scheduler works:
The data in Linux is placed in a form of file system.
Types of file system:
There are 3 types of file in Linux:
All the data, page instructions or text
are stored in ordinary file.
It is like a folder. It store files that
are lists of both the ordinary and special files.
Special files supports input and output
mechanism and it also gives access to hardware.
Some common listing of files:
Listing of all files:
To list all the files:
We use * after the character to list all the files
starting with it:
To list all the hidden files we use –a:
In this report, we have discussed the architecture,
memory, scheduling and file system of Linux Operating System.