basys (3) --- basic computer system simulator 02/23/82 _U_s_a_g_e basys _D_e_s_c_r_i_p_t_i_o_n 'Basys' is a program designed to simulate a basic computer system configuration consisting of a central processing unit, a disk drive and a central memory. It is a distribu- tion driven simulator. In other words, the work load under which the system is to be simulated is characterized by probability distributions for such factors as the time between job arrivals, the priority of a job, the amount of memory required by a job, the number of i/o requests a job will make, and so on. When invoked, 'basys' asks the user for the following information: - sssiiimmmuuulllaaatttiiiooonnn llleeennngggttthhh The number of seconds for which the simulation run should last is given here. Note that this is simulated time, not real time. - mmmeeemmmooorrryyy sssiiizzzeee This is the size of main memory in K-words. All jobs generated by the simulator have memory requirements in the range 2K to 70K words; thus, the memory size specified should probably be greater than or equal to 70. - tttiiimmmeee tttooo cccooommmpppaaacccttt mmmeeemmmooorrryyy This is the amount of time in microseconds required to compress memory to make space available for a job. - pppeeerrr wwwooorrrddd dddiiissskkk tttrrraaannnsssfffeeerrr tttiiimmmeee This is the time in microseconds required to transfer one word between disk and memory. - dddiiissskkk aaacccccceeessssss tttiiimmmeee This is the time in milliseconds required to position the disk head over the desired sector before a transfer takes place. It includes both seek time and rotational latency. - iii///ooo ooovvveeerrrhhheeeaaaddd tttiiimmmeee This is the overhead time in microseconds involved in the initiation of an i/o request. - mmmeeeaaannn jjjooobbb iiinnnttteeerrraaarrrrrriiivvvaaalll tttiiimmmeee The time in milliseconds between job arrivals is generated from an exponential distribution whose mean is specified here. basys (3) - 1 - basys (3) basys (3) --- basic computer system simulator 02/23/82 - mmmeeeaaannn cccpppuuu tttiiimmmeee pppeeerrr jjjooobbb The number of milliseconds of cpu time required by each job is generated from a normal distribution whose mean and standard deviation are specified by this parameter and the next. - ssstttaaannndddaaarrrddd dddeeevvviiiaaatttiiiooonnn ooofff cccpppuuu dddiiissstttrrriiibbbuuutttiiiooonnn The standard deviation (in milliseconds) of the per-job cpu time distribution. - mmmeeeaaannn nnnuuummmbbbeeerrr ooofff iii///ooo rrreeeqqquuueeessstttsss pppeeerrr jjjooobbb The number of i/o requests that a job will make is determined by a normal distribution for which the mean value is specified here. - ssstttaaannndddaaarrrddd dddeeevvviiiaaatttiiiooonnn ooofff iii///ooo dddiiissstttrrriiibbbuuutttiiiooonnn The standard deviation of the distribution from which the per-job number of i/o requests is generated is specified here. - mmmiiinnniiimmmuuummm rrreeecccooorrrddd sssiiizzzeee This is the minimum number of words in a single i/o transfer. All transfers requested by a single job involve the same number of words. - mmmaaaxxxiiimmmuuummm rrreeecccooorrrddd sssiiizzzeee The maximum number of words in an i/o transfer is specified here. - eeevvveeennnttt tttrrraaaccceee If the user responds with "yes", 'basys' will print on standard output two a listing of all pertinent events as they are scheduled and as they occur. Events traced are job arrival, memory request, cpu request, cpu release, disk request, disk release and job termination. WARNING: under reasonable durations of simulation, the volume of output produced by this option is prohibitively large. Upon completion of the simulation, 'basys' prints on stan- dard output one a three part report. The first part is a summary of system parameters as specified by the user. The second part is a table of job descriptions, sorted by ascen- ding job number. The table gives a profile of each job that entered the system during the simulation run. Finally, a summary of how well the system performed is printed. Included in this part are statistics on utilization of the three system resources: memory, cpu and disk, as well as statistics on the wait queues for each of these resources. _E_x_a_m_p_l_e_s parameters> basys basys >report >event_trace basys (3) - 2 - basys (3) basys (3) --- basic computer system simulator 02/23/82 _B_u_g_s Meaningless results accompany meaningless input. Locally supported. basys (3) - 3 - basys (3)