implemented priority scheduling
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8D83DE470F8544E7
224
simulator.c
224
simulator.c
@ -8,6 +8,7 @@
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enum pstate {
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WAITING,
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READY,
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RUNNING,
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FINISHED
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};
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@ -18,13 +19,25 @@ struct pinfo {
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int priority;
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int wait_time;
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int completion_time;
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int turnaround_time;
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int remaining_time;
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int n_preempted;
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enum pstate state;
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struct pinfo * next_pinfo;
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};
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int n_processes(struct pinfo * head) {
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int n = 0;
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while (head != NULL) {
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n++;
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head = head->next_pinfo;
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}
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return n;
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}
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struct perf_info {
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int total_time;
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int total_nr_ctxt_switch;
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@ -44,7 +57,7 @@ void print_pinfo(struct pinfo * info) {
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printf(" Execution time: %d\n", info->execution_time);
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printf(" Priority: %d\n", info->priority);
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printf(" Wait time: %d\n", info->wait_time);
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printf(" Completion time: %d\n", info->completion_time);
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printf(" Turnaround time: %d\n", info->turnaround_time);
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printf(" Remaining time: %d\n", info->remaining_time);
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printf(" NEXT -> %p\n", info->next_pinfo);
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printf("}>\n");
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@ -64,8 +77,9 @@ struct pinfo * create_process(int id, int arrival_time, int execution_time, int
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info->execution_time = execution_time;
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info->priority = priority;
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info->wait_time = 0;
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info->completion_time = 0;
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info->turnaround_time = 0;
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info->remaining_time = execution_time;
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info->n_preempted = 0;
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info->state = WAITING;
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info->next_pinfo = NULL;
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return info;
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@ -83,8 +97,8 @@ struct perf_info schedule_FCFS(struct pinfo * processes) {
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wait_time = 0;
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}
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process->wait_time = wait_time;
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process->completion_time = process->execution_time + process->wait_time;
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current_time = process->arrival_time + process->completion_time;
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process->turnaround_time = process->execution_time + process->wait_time;
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current_time = process->arrival_time + process->turnaround_time;
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process = process->next_pinfo;
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}
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@ -93,6 +107,201 @@ struct perf_info schedule_FCFS(struct pinfo * processes) {
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return perf;
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}
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struct prio_list {
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struct pinfo ** proc;
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int length;
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};
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/**
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* Pops and returns the last element (highest priority) of the given priority list
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*
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* Returns NULL if the list is empty
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*/
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struct pinfo * prio_list_pop(struct prio_list * list) {
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if (list->length == 0) {
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return NULL;
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}
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list->length--;
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return *(list->proc + list->length);
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}
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/**
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* Adds the given process in the priority list at
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* the appropriate place (according to its priority)
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*/
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void prio_list_add(struct prio_list * list, struct pinfo * proc) {
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struct pinfo * proc2;
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int idx = 0;
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// Find first element (from the right) with lower priority
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for (int i=list->length-1; i>=0; i--) {
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proc2 = *(list->proc + i);
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if (proc2->priority > proc->priority) {
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idx = i+1;
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break;
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}
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}
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// Shift elements
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for (int j=list->length-1; j>=idx; j--) {
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*(list->proc + j + 1) = *(list->proc + j);
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}
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*(list->proc + idx) = proc;
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list->length++;
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}
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/**
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* Creates a new priority list
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*/
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struct prio_list * create_prio_list(int max_size) {
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struct pinfo ** processes = (struct pinfo **) malloc(sizeof(struct pinfo *) * max_size);
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struct prio_list * list = (struct prio_list *) malloc(sizeof(struct prio_list));
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list->length = 0;
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list->proc = processes;
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return list;
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}
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/**
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* Returns the last element (highest priority) of the given priority list
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*/
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struct pinfo * prio_list_last(struct prio_list * list) {
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return *(list->proc + list->length - 1);
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}
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/**
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* Prints the pids of the processes in the given priority list
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*/
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void prio_list_print(struct prio_list * list) {
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printf("queue: ");
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for (int i=0; i < list->length; i++) {
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if (i != 0) {
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printf(", ");
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}
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printf("%d", (*(list->proc + i))->id);
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}
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printf("\n");
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}
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struct perf_info schedule_Pr(struct pinfo * processes) {
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struct perf_info perf = {0, 0, 0};
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int current_time = 0;
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struct pinfo * current = NULL;
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struct pinfo * next = processes;
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int N = n_processes(processes);
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printf("N = %d\n", N);
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struct prio_list * queue = create_prio_list(N);
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int finished = 0;
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while (finished != N) {
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printf("\nCurrent time: %d / ", current_time);
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if (current != NULL) {
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printf("Current: %d / ", current->id);
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} else {
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printf("Current: none / ");
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}
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if (next != NULL) {
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printf("Next: %d\n", next->id);
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} else {
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printf("Next: none\n");
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}
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if (current == NULL) {
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printf("No running process: running %d\n", next->id);
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current = next;
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current->state = RUNNING;
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next = next->next_pinfo;
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} else if (next != NULL) {
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next->state = READY;
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prio_list_print(queue);
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printf("Processing next process (%d)\n", next->id);
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// If current finished before next
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while (current != NULL && current_time + current->remaining_time <= next->arrival_time) {
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printf(" Process %d finished before next\n", current->id);
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current->state = FINISHED;
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current_time += current->remaining_time;
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current->turnaround_time = current_time - current->arrival_time;
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current->remaining_time = 0;
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finished++;
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current = prio_list_pop(queue);
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}
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if (current != NULL) {
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printf("Removing time from current process\n");
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current->remaining_time -= next->arrival_time - current_time;
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current->turnaround_time += next->arrival_time - current_time;
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}
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if (next->arrival_time > current_time) {
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current_time = next->arrival_time;
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}
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next->state = READY;
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// If no running process, immediately run next process
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if (current == NULL) {
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printf("Queue is empty, running next process %d\n", next->id);
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current = next;
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current->state = RUNNING;
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next = next->next_pinfo;
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} else if (next->priority < current->priority) {
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// Preempt current process
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printf("Next process (%d) has higher priority\n", next->id);
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if (current->state == RUNNING) {
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printf(" Preempting current process (%d)\n", current->id);
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current->n_preempted++;
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current_time += CNTXT_SWITCH;
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perf.total_nr_ctxt_switch++;
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}
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current->state = READY;
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prio_list_add(queue, current);
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// Run process with higher priority
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current = next;
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current->state = RUNNING;
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next = next->next_pinfo;
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} else {
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printf("Adding next process (%d) to list\n", next->id);
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prio_list_add(queue, next);
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next = next->next_pinfo;
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}
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if (current != NULL) {
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current->state = RUNNING;
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}
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} else {
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printf("No new processes, emptying queue\n");
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while (current != NULL) {
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printf("Completing process %d\n", current->id);
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current->state = FINISHED;
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current_time += current->remaining_time;
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current->turnaround_time = current_time - current->arrival_time;
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current->remaining_time = 0;
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finished++;
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current = prio_list_pop(queue);
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if (current != NULL) {
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current->state = RUNNING;
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}
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}
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}
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}
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perf.total_time = current_time;
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perf.total_time_ctxt_switch = perf.total_nr_ctxt_switch * CNTXT_SWITCH;
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return perf;
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}
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void compute_waiting_time(struct pinfo * processes) {
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while (processes != NULL) {
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processes->wait_time = processes->turnaround_time - processes->execution_time;
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processes = processes->next_pinfo;
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}
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}
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struct pinfo * read_file() {
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FILE * file = fopen("tasks.csv", "r");
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@ -154,7 +363,10 @@ void free_processes(struct pinfo * next) {
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int main() {
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struct pinfo * processes = read_file();
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struct perf_info perf = schedule_FCFS(processes);
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//struct perf_info perf = schedule_FCFS(processes);
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struct perf_info perf = schedule_Pr(processes);
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compute_waiting_time(processes);
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//write_file(processes, &perf);
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print_processes(processes);
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