Process Scheduler

A simple process scheduling simulator. The goal for this project is to get a basic but complete simulation of the process scheduling algorithm used by modern Operative Systems.

  npm install --save process-scheduler

Domain

• Hardware Resources

  • Processor - Represents the hardware CPU.

    • speed - Processor computation speed.
    • compute - Computes a given operation.

  • Memory - Represents the RAM

    • availableMemory - in bytes
    • speed - Memory allocation speed.

  • Disc - Represents the available secondary memory. (HDD)

    • availableSpace - in bytes

  • Devices - Represents an external device the computer can interact with.

• System

  • processors - Available processors on the machine.
  • primaryMemory - All RAM resources available.
  • devices - All available devices to the operating system (those which have a running driver).
  • generatePID - Generates a new unique PID.
  • getAvailableProcessor - Returns an available processor (the one with less work load). If there are not available processors, then this throws an error indicating there are not resources.
  • allocateMemory(memory) - Allocates a given amount of memory ram. If there is not enough memory to allocate, an error is thrown indicating it.
  • deallocateMemory(memory) - Deallocates a given amount of memory ram.

• Scheduler

  • states - Process possible states - New, Ready, Running, Waiting or Terminated.
    • queue - Each state process queue.
  • _transitions - Possible transitions between process states (Accepted, Run, Block, Exit)
  • scheduleProcess(pid, process) - Schedule a new process. The process starts at New state (added to the new queue). Emits the event transition, with a property transition.name set to STATE on each state transition.
    • NEW:
      • The process is added to the NEW queue.
      • The new process waits until is ready to be allocated. If there are enough resources the process transition to the READY state. If there are not enough resources, then the process is kept on the NEW queue until more resources are available.
    • READY
      • If the computation is done before the process quantum expiration, the process transition to the TERMINATED state.
      • If the computation takes more time than the quantum expiration, the process transition to the READY state and the resources are deallocated.
      • If the computation requires some external resource (device) or needs to wait for other resource to end its computation, the process transition to the WAITING state and the resources are deallocated.
    • TERMINATED
      • The process lifecycle has ended. The resources are deallocated.
    • WAITING
      • The process is waiting for some external operation to end.
      • Once the external operation is finished, the process is moved to the READY state.

• Process - the running entity of a given program.

  • fileName - path to file which contains the program code.
  • name - process name
  • stack - Stack of functions or procedures calls made by the program.
  • heap - Memory segment used to allocate values.

• Process Control Block - One per process running on the operative system. Handles the operations that can be achieved for the process.

  • PID - Collision free number autogenerated by the operative system.
  • nextPCB - Pointer to the next process in the PCB queues.
  • pointerControl - The actual process state.
  • processor - The assigned processor.
  • priority - Process priority. Taken in account on process scheduling queues.
  • quantum - Maximum amount of time allowed to be assigned to a processor.
  • state - Process current state. See scheduler.states.
  • Resources Allocation
    • memoryToAllocate - Amount of memory this process will allocate.
    • data - Available data space
  • computing - The time this process requires to ends its computation.
  • resources - Indicates the resources the process requires.
    • time: Since this is simulator, is just a delay of the time the resource waiting signal would delay.
    • name: One of the available devices.
  • The process emits a finished event when its computation is done.