Process Scheduling Simulation

CONFIGURATIONS - Alter to vary simulation results

Simulate all the algorithms.

const bool SIMULATE_ALL_SCHEDULING_ALGORITHMS = true;

Scheduling algorithm to use. Implemented algos- SCHEDULING_FCFS, SCHEDULING_SJF, SCHEDULING_PRIORITY, SCHEDULING_ROUND_ROBIN

const int SCHEDULING_ALGORITHM = SCHEDULING_ROUND_ROBIN;

Time quantum (in milliseconds) to be used. This is used in case of Round-Robin scheduling algorithm. This is the maximum time window a job will be allocated for execution. If the job completes in this duration, then the next job is processed. Otherwise, the job is paused and its state is saved. The scheduler will process other jobs for this time quantum again and return back to process this job again.

const long long TIME_QUANTUM = 500;

This parameter identifies the jobs whose response time period exceeds the permissible value in comparison to its time required for completion. So for instance if a job requires 200ms. to complete and if the response time threshold is 2, then response time threshold for this job is 400ms.

const int RESPONSE_TIME_THRESHOLD = 2;

Number of jobs for which simulation has to be done. Use '-1' to create jobs continuously.

const long int JOBS_TO_CREATE = 1000;

Show details of job running status

const bool SHOW_JOB_STATUS = false;

Use random sleep duration for creation thread

const bool USE_RANDOM_JOB_CREATION_SLEEP = false;

Seconds to wait before displaying statistics. Use -1 to display the stats only at the end of simulation. Be careful though, if the simulation is run without a finite number of jobs, no stats would be shown.

const int STATS_DISPLAY_INTERVAL = 10;

Max time duration (ms) before proceeding to create another job. This means that before creating a new job, the system will wait for any value in b/w 0 to JOB_CREATION_SLEEP_MAX-1 seconds.

const int JOB_CREATION_SLEEP_MAX = 1000;

Milliseconds before proceeding to create another job

const int JOB_CREATION_SLEEP_CONST = 1000;

Program Description

This program simulates the Process Scheduling. First a scheduler has to be created. Following are supported:

1. FCFS (First-come First-served)
2. Priority Scheduling
3. SJF (Shortest Job First)
4. Round Robin
5. Multi-level feedback queue

This has been implemented by inheriting from the ProcessScheduler class. Depending on the name of the algorithm, derived class for that particular scheduler is created.

Jobs with an ID and a random priority are continuously created by an RNG (Random Number Generator). The job creator is a separate thread. This is done so as to simulate scenarios where pre-emption is required.

The scheduler is then started with ProcessJobs() API. It will keep on processing the jobs present in the pending job pool list.