Operating system experiment three, process scheduling simulation program

Experiment Three Process Scheduling Simulation program

Major: Shang Soft second class name: Jiang Zhibin No.: 201406114225

1. ExperimentsPurpose and requirements

1.1. Purpose of the experiment

A process scheduler is completed in a high-level language to deepen the understanding of process concepts and process scheduling algorithms.

1.2. Experimental Requirements

1.2.1 Example: design a process scheduling simulation program with n processes executing concurrently.

Process scheduling algorithm: Using the highest priority scheduling algorithm (that is, the processor is assigned to the highest priority process) and first-come first service (if the same priority) algorithm.

(1). Each process has a Process Control block (PCB) representation. The Process Control block contains the following information: Process name, priority, arrival time, required run time, elapsed CPU time, process state, and so on.

(2). The priority of the process and the desired run time can be specified in advance, and the running time of the process is calculated in time slices.

(3). The state of each process can be either ready, running R (Running), or completing one of the three states of F (finished).

(4). The ready process can only run one time slice after the CPU is acquired. Represented by the elapsed CPU time plus.

(5). If the elapsed CPU time of a process has reached the desired run time after a time slice is run, the process is undone, and if the elapsed CPU time of the process after running a time slice has not reached the required run time, that is, the process needs to continue running, the priority number of the process should be reduced by 1 (that is, lowering the first , and then insert it into the ready queue for scheduling.

(6). Each time the scheduler is run, the PCB for each process in the running process and ready queue is printed for inspection.

(7). Repeat the process until the process is complete.

Thinking: What is the difference between job scheduling and process scheduling?

1.2.2 experimental question A: write and debug a simulated process scheduler, using the "highest priority priority" scheduling algorithm to n (n not less than 5) process scheduling.

The basic idea of the "highest priority priority" scheduling algorithm is to allocate the CPU to the process with the highest number of priorities in the ready queue.

(1). The static precedence number is determined when the process is created and no longer changes during the entire process run.

(2). The dynamic precedence number refers to the process's priority number, which can be given an initial value when the process is created, and the priority number can be modified by a certain rule. For example, when a process obtains a CPU, it reduces its priority by 1, and the process waits longer than a certain time period (2 timecode time) to increase its priority number, and so on.

(3). (*) The priority number of the process and the running time required can be specified in advance (or can be generated by random numbers).

(4). (*) The process can be created (incremented) during the simulation scheduling process, and its arrival time is the time that the process entered.

1.2.3 experimental question B: write and debug a simulated process scheduler, using "time-slice rotation" scheduling algorithm to n (n not less than 5) process scheduling. The "Rotation method" has the simple rotation method and the multilevel feedback queue scheduling algorithm.

(1). The basic idea of the simple rotation method is that all ready processes FCFS into a queue, always assigning the processor to the team's first process, and each process takes on the same length of time slices of the CPU. If the running process has not finished using its time slice, send it back to the end of the ready queue and reassign the processor to the team's first process. Until all processes have finished running. (Is there a priority for this scheduling algorithm?) ）

(2). The basic idea of the multilevel feedback queue scheduling algorithm is:

The ready queue is divided into N-level (N=3~5), each ready queue has different precedence and is assigned to different time slices: the higher the queue level, the lower the priority number, the longer the time slice, and the smaller the priority, the shorter the time slice.

The system is scheduled from the first level, when the first level is empty, the system turns to the second level queue, ... When the running process runs out of time slices, it discards the CPU and enters the next level queue if it is not completed.

When the process is first ready, it enters the first-level queue.

(3). (*) Consider the blocking State B (Blocked) of the process to increase the blocking queue. The time at which the process is blocked and blocked is determined by the resulting "random number" (the frequency and length of the blocking is more reasonable). Note that a process can be converted to a blocking state only if it is in a running state, and the process is only ready to be converted to a running state.

2.Experimental content

According to the assigned experimental subjects: A (1), A (2), B (1) and B (2)

Complete the design, coding and commissioning work, complete the experiment report.

Note: The entry with the * * number indicates the selection.

3.Experimental environment

Turbo C can be chosen as the development environment. You can also choose a visual environment such as VB,CB under Windows, which makes it easy to use various controls. Choose the experimental environment independently.

4. Experiment principle and core algorithm reference program segment

Dynamic precedence (The priority number is reduced only):

Source:

#include <stdio.h>#include<stdlib.h>#include<string.h>#defineMax 100typedefstructpcb{CharName[max];//Process Name    intPriority//Priority Level    intArrtime;//Arrival Time    intNeedtime;//Run time required    intUsedtime;//used Time    CharState//process Status}PCB; PCB Pcb[max]; intn=1;intPtime;//time slicesCharSelectmenu ();voidInput ();voidSort ();voidPrint ();voidAttemper ();CharSelectmenu () {Char Select; printf ("function Menu:"); printf ("\ n 1. Increase and dispatch the process"); printf ("\ n 2. Printing process"); printf ("\ n 3. Exit"); printf ("\ n Please enter your choice (1--3):");  Do{        Select=GetChar (); } while(Select!='1'&&Select!='2'&&Select!='3'); return Select;}voidMain () {intchoice; N=1; printf ("\ n"); printf ("\t\t Welcome to the use of process scheduling simulation \ n"); Choice=Selectmenu ();  Do{        if(choice=='1') {printf ("\ n"); printf ("Please set the size of the time slice:"); scanf ("%d",&ptime);            Input ();            Print ();        Attemper (); }        if(choice=='2') {Print (); }        if(choice=='3')        {            return; } Choice=Selectmenu (); } while(1);}voidInput () { Do{printf ("\ n---Please enter the process of%d processes---\ n", N); printf ("\ n Process Name:"); scanf ("%s", Pcb[n].name); printf ("Process Priority:"); scanf ("%d",&pcb[n].priority); printf ("time required for the process:"); scanf ("%d",&pcb[n].needtime); Pcb[n].arrtime=N; Pcb[n].usedtime=0; Pcb[n].state='W'; N++; } while(n<5);}voidSort () {inti,j;    PCB temp;  for(i=0; i<n-1; i++)//Sort by arrival time    {         for(j=n-2; j>=i;j--)        {            if(pcb[j+1].arrtime<pcb[j].arrtime) {Temp=Pcb[j]; PCB[J]=pcb[j+1]; Pcb[j+1]=temp; }        }    }          for(i=0; i<n-1; i++)//Sort by Priority    {         for(j=n-2; j>=i;j--)        {            if(pcb[j+1].priority>pcb[j].priority) {Temp=Pcb[j]; PCB[J]=pcb[j+1]; Pcb[j+1]=temp; }        }    }    if(pcb[0].state!='F') {pcb[0].state='R'; }}voidPrint () {inti;    Sort (); printf ("\ n Process name priority arrival time takes time to use time process state \ n");  for(i=0; i<n;i++) {printf ("%8s%8d%8d%10d%10d%10c\n", pcb[i].name,pcb[i].priority,pcb[i].arrtime,pcb[i].needtime,pcb[i].usedtime,pcb[i].state); }}voidAttemper () { Do{        if((pcb[0].needtime-pcb[0].usedtime) >ptime)//determines whether the remaining elapsed time of the process is greater than the time slice{pcb[0].usedtime+=Ptime; pcb[0].priority--; pcb[0].state='W'; }        Else                       //completed Processes{pcb[0].usedtime=pcb[0].needtime; pcb[0].priority=-1; pcb[0].state='F';    } Print (); } while(pcb[0].state!='F');}

Operation Result:

 

Operating system experiment three, process scheduling simulation program