Library prosa.classic.model.schedule.uni.limited.abstract_RTA.abstract_seq_rta

Abstract Response-Time Analysis with sequential jobs

In this module we propose the general framework for response-time analysis (RTA) of uniprocessor scheduling of real-time tasks with arbitrary arrival models and sequential jobs.
Module AbstractSeqRTA.

  Import Job ArrivalCurves TaskArrival ScheduleOfTask UniprocessorSchedule Workload
         Service ResponseTime MaxArrivalsWorkloadBound
         AbstractRTADefinitions AbstractRTALockInService AbstractRTAReduction AbstractRTA.

  Section Sequential_Abstract_RTA.

    Context {Task: eqType}.
    Variable task_cost: Task time.

    Context {Job: eqType}.
    Variable job_arrival: Job time.
    Variable job_cost: Job time.
    Variable job_task: Job Task.

    Variable arr_seq: arrival_sequence Job.
    Hypothesis H_arrival_times_are_consistent: arrival_times_are_consistent job_arrival arr_seq.
    Hypothesis H_arr_seq_is_a_set: arrival_sequence_is_a_set arr_seq.

    Variable sched: schedule Job.
    Hypothesis H_jobs_come_from_arrival_sequence: jobs_come_from_arrival_sequence sched arr_seq.

    Hypothesis H_jobs_must_arrive_to_execute: jobs_must_arrive_to_execute job_arrival sched.
    Hypothesis H_completed_jobs_dont_execute: completed_jobs_dont_execute job_cost sched.

    Hypothesis H_job_cost_le_task_cost:
      cost_of_jobs_from_arrival_sequence_le_task_cost
        task_cost job_cost job_task arr_seq.

    Let job_pending_at := pending job_arrival job_cost sched.
    Let job_completed_by := completed_by job_cost sched.
    Let arrivals_between := jobs_arrived_between arr_seq.
    Let task_scheduled_at := task_scheduled_at job_task sched.
    Let response_time_bounded_by :=
      is_response_time_bound_of_task job_arrival job_cost job_task arr_seq sched.

    Variable ts: list Task.

    Hypothesis H_all_jobs_from_taskset:
       j, arrives_in arr_seq j job_task j \in ts.

    Variable max_arrivals: Task time nat.
    Hypothesis H_family_of_proper_arrival_curves:
      family_of_proper_arrival_curves job_task arr_seq max_arrivals ts.

    Variable tsk: Task.
    Hypothesis H_tsk_in_ts: tsk \in ts.

    Variable job_lock_in_service: Job time.
    Variable task_lock_in_service: Task time.

    Hypothesis H_proper_job_lock_in_service:
      proper_job_lock_in_service job_cost arr_seq sched job_lock_in_service.

    Hypothesis H_proper_task_lock_in_service:
      proper_task_lock_in_service
        task_cost job_task arr_seq job_lock_in_service task_lock_in_service tsk.

    Variable interference: Job time bool.
    Variable interfering_workload: Job time time.

    Let task_rbf := task_request_bound_function task_cost max_arrivals tsk.
    Let work_conserving := work_conserving job_arrival job_cost job_task arr_seq sched tsk.
    Let busy_intervals_are_bounded_by := busy_intervals_are_bounded_by job_arrival job_cost job_task arr_seq sched tsk.
    Let job_interference_is_bounded_by := job_interference_is_bounded_by job_arrival job_cost job_task arr_seq sched tsk.
    Let busy_interval := busy_interval job_arrival job_cost sched interference interfering_workload.
    Let task_workload_between := task_workload_between job_cost job_task arr_seq tsk.
    Let arrivals_of_task_before := arrivals_of_task_before job_task arr_seq.
    Let task_service_between := task_service_between job_task arr_seq sched tsk.

    Section Definitions.

      Definition interference_and_workload_consistent_with_sequential_jobs :=
         j t1 t2,
          arrives_in arr_seq j
          job_task j = tsk
          job_cost j > 0
          busy_interval j t1 t2
          task_workload_between 0 t1 = task_service_between 0 t1.

      Definition task_interference_received_before (tsk: Task) (upper_bound: time) (t: time) :=
        (~~ task_scheduled_at tsk t)
          && has (fun jinterference j t) (arrivals_of_task_before tsk upper_bound).

      Definition cumul_task_interference tsk upper_bound t1 t2 :=
        \sum_(t1 t < t2) task_interference_received_before tsk upper_bound t.

      Definition task_interference_is_bounded_by (task_interference_bound_function: Task time time time) :=
         j R t1 t2,
          arrives_in arr_seq j
          job_task j = tsk
          t1 + R < t2
          ~~ job_completed_by j (t1 + R)
          busy_interval j t1 t2
          let offset := job_arrival j - t1 in
          cumul_task_interference tsk t2 t1 (t1 + R) task_interference_bound_function tsk offset R.

    End Definitions.

    Section ResponseTimeBound.

      Let cumul_interference := cumul_interference interference.
      Let cumul_workload := cumul_interfering_workload interfering_workload.
      Let cumul_task_interference := cumul_task_interference tsk.

      Hypothesis H_work_conserving: work_conserving interference interfering_workload.

      Hypothesis H_sequential_jobs: sequential_jobs job_arrival job_cost sched job_task.
      Hypothesis H_interference_and_workload_consistent_with_sequential_jobs:
        interference_and_workload_consistent_with_sequential_jobs.

      Variable L: time.
      Hypothesis H_busy_interval_exists: busy_intervals_are_bounded_by interference interfering_workload L.

      Variable task_interference_bound_function: Task time time time.
      Hypothesis H_task_interference_is_bounded: task_interference_is_bounded_by task_interference_bound_function.

      Let total_interference_bound tsk A Δ :=
        task_rbf (A + ε) - task_cost tsk + task_interference_bound_function tsk A Δ.

      Let is_in_search_space_seq := is_in_search_space tsk L total_interference_bound.

      Variable R: nat.
      Hypothesis H_R_is_maximum_seq:
         A,
          is_in_search_space_seq A
           F,
            A + F = (task_rbf (A + ε) - (task_cost tsk - task_lock_in_service tsk))
                    + task_interference_bound_function tsk A (A + F)
            F + (task_cost tsk - task_lock_in_service tsk) R.

      Section CompletionOfJobsFromSameTask.

        Variable j1 j2: Job.
        Hypothesis H_j1_arrives: arrives_in arr_seq j1.
        Hypothesis H_j2_arrives: arrives_in arr_seq j2.
        Hypothesis H_j1_from_tsk: job_task j1 = tsk.
        Hypothesis H_j2_from_tsk: job_task j2 = tsk.
        Hypothesis H_j1_cost_positive: job_cost_positive job_cost j1.

        Variable t1 t2: time.
        Hypothesis H_busy_interval: busy_interval j1 t1 t2.

        Lemma completed_before_beginning_of_busy_interval:
          job_arrival j2 < t1
          completed_by job_cost sched j2 t1.

        Lemma arrives_after_beginning_of_busy_interval:
           t,
            t1 t
            job_pending_at j2 t
            arrived_between job_arrival j2 t1 t.+1.

      End CompletionOfJobsFromSameTask.


      Section BoundOfCumulativeJobInterference.

        Variable j: Job.
        Hypothesis H_j_arrives: arrives_in arr_seq j.
        Hypothesis H_job_of_tsk: job_task j = tsk.
        Hypothesis H_job_cost_positive: job_cost_positive job_cost j.

        Variable t1 t2: time.
        Hypothesis H_busy_interval: busy_interval j t1 t2.

        Let A := job_arrival j - t1.

        Variable x: time.
        Hypothesis H_inside_busy_interval: t1 + x < t2.
        Hypothesis H_job_j_is_not_completed: ~~ job_completed_by j (t1 + x).

        Lemma bound_for_cumulative_job_interference_actual:
          cumul_interference j t1 (t1 + x)
          (task_workload_between t1 (t1 + A + ε) - job_cost j) + cumul_task_interference t2 t1 (t1 + x).

        Lemma task_rbf_excl_tsk_bounds_task_workload_excl_j:
          task_workload_between t1 (t1 + A + ε) - job_cost j task_rbf (A + ε) - task_cost tsk.

        Lemma bound_for_cumulative_job_interference:
          cumul_interference j t1 (t1 + x)
             (task_rbf (A + ε) - task_cost tsk) + cumul_task_interference t2 t1 (t1 + x).

      End BoundOfCumulativeJobInterference.

      Section MaxInSeqHypothesisImpMaxInNonseqHypothesis.

        Variable j: Job.
        Hypothesis H_j_arrives: arrives_in arr_seq j.
        Hypothesis H_job_of_tsk: job_task j = tsk.

        Let is_in_search_space A :=
          is_in_search_space tsk L total_interference_bound A.

        Lemma max_in_seq_hypothesis_implies_max_in_nonseq_hypothesis:
           A,
            is_in_search_space A
             F,
              A + F = task_lock_in_service tsk +
                      (task_rbf (A + ε) - task_cost tsk + task_interference_bound_function tsk A (A + F))
              F + (task_cost tsk - task_lock_in_service tsk) R.

      End MaxInSeqHypothesisImpMaxInNonseqHypothesis.

      Theorem uniprocessor_response_time_bound_seq:
        response_time_bounded_by tsk R.
    End ResponseTimeBound.

  End Sequential_Abstract_RTA.

End AbstractSeqRTA.