3.8) Scheduler: Scheduler in an operating system selects the next process to be admitted into the system and next process to run. The three schedulers and their differences are as follows:-
Long Term Scheduler: Long term scheduler also known as job scheduler, selects the process or jobs which are to be allowed to the ready queue in the main memory for execution. It decides what processes are to be run on the system. Long term scheduling has much less frequency of execution. The long term scheduler is responsible for controlling the degree of multiprogramming. Because of longer periods between the executions, long term scheduler has an ability to take time in selecting the process for execution. It is important to select an appropriate process. Generally processes can be described as I/O bound or CPU bound. I/O bound spends more time in doing I/O operations rather than other computations. CPU bound is contrast to I/O bound, which spends time doing all other
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It has a thread ID, a program counter, a register set, and a stack. Thread is smaller than a process so thread creation needs only some resources when with a process creation. In creating a process, it requires to allocate the process control block (PCB).The PCB includes a memory map and list of open files. A process creation makes memory being allocated for program instructions and data.
4.11) Concurrency: A condition that exists when at least two threads are in progress. Parallelism: A condition that exists when two threads are executing in parallel. Yes it is possible to have concurrency but not parallelism. This can be explained as: If there are 4 threads and they are executed on a single computing or multiple computing system, the threads will be in progress even though they do not execute in parallel way. This condition satisfies concurrency but no parallelism. But it is not possible to have parallelism without
Process view- this describes a system’s processes, it shows any communication between those processes, explores what needs to happen inside the system. Particularly helpful when your system will have a number of simultaneous threads or processes. And uml activity diagrams represent the process view.
Processing unit: It consists of a processor (microcontroller) and storage (RAM). In addition, it has operating systems as well as a timer. The responsibility of the processing unit includes collecting data from various sources then processing and storing. A timer is used to do the sequencing for the processes. This is basically where the
The Central Processing Unit (CPU) is a computer component that converts data input into information output. It is a complicated and broad set of electronic circuits that performs compiled instructions. All computers and laptops must have a central processing unit to operate as it acts as the ‘brain’ of the device. There are numerous ways of referring to a CPU, such as processor, microprocessor or central processor. Compared to some older models, the more recent models are small, square and have connectors underneath it. The CPU is attached to the slot or socket of the motherboard. It is usually secured and held down by a small lever.
The scheduling of Linux operating system is priority based scheduling. It is to make scheduling policies into the core of Linux which called Kernel for multi-tasking processes. There are two different scheduling: real time and normal, for handling large data processes performance balance and sharing CPU equally in the system. In the scheduling of Kernel, each process has a priority value which ranges from 1 to 139. 1 is the highest priority level. 139 is the lowest priority level. The real time priorities range from 1 to 99 and the normal priorities range from 100 to 139. The smaller number of priority value, the priority is higher. All real time programs have a higher priority than normal programs in the system. In Linux scheduling is implemented by a class named sched_class (Seeker, 2013).
In the first step of dealing with a CPU the fetch function is up first. The fetch function involves retrieving information that it needs to run from the program memory, and basically giving it instructions which is put in by a number of a whole line of them from the memory. Wherever the memory may be is determined by the (PC) which is also known as the program counter. The PC stores a number that can keep track of the current place in the program. When the instruction is fetched the Program Counter is then inputted by the length of the instruction in word terms of the
Computers today have developed from running single program capability and running run one program at a time to having the ability to run multiple programs at the same time. They are also able to use multiple threads to provide more than one task to be run at the same time. Processes were created to help manage the execution of the programs. A process is defined as a unit of work in a modern time-sharing system during the execution of a program. There are five states that a process may be in new, running, waiting, ready, and terminated. Only one process can be running on a processor and the other processes are in a ready and waiting state.
Procedure is set of coded instruction that tells a computer how to run a program and calculation and performs a specific task.
Therefore, the execution rate of all tasks is the same among all processors. Hence, the scheduling
Multithreading is the ability of operating system to run divide and run different parts of a process on a single CPU to obtain the same but fast result. Different parts of the code which run simultaneously are called
To improve the quality of services and maintaining the efficiency and fairness among the jobs the scheduler
Multiprocessing is the support of more than one processor at the same time. Applications in a multi-processing system are broken into smaller routines that run by themselves.
Microprocessor - This is the heart of your computer. It performs instructions and controls the operation of the computer.
sensors, motion detectors etc.). Almost all programs require some sort of input and produces output. This involves the use of I/O operations. The operating system hides the low level hardware communication for I/O operations from the user. User only specifies device and the operation to perform, and only see that I/O has been performed (i.e. choosing one of the printer in office for printing service). For security and efficiency, user level programs cannot control I/O operations. Therefore, the operating system must facilitate these services.
If a process took 45 minutes then the user would have to run 2 blocks simultaneously, taking up 1 hour, this means 15 minutes would be wasted, as the process wouldn’t actually take that long. This means that running a number of processes would take too long. This is considered Phase 1 of Operating systems and is called Serial Processing
7) A ___ timer _______ is set at the beginning of each job to prevent any single job from monopolizing the system.