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add counter to the task control block to determine the computation time

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- the counter represents the time at which the task is scheduled on the
  cpu
- if two or more tasks are running on the same cpu, we use this value to
  determine an expired time slice
=> task switching for round-robin scheduling
This commit is contained in:
Stefan Lankes 2016-09-22 18:18:27 +02:00
parent 01f0862aa7
commit fbaf77c8fd
2 changed files with 23 additions and 3 deletions
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2
hermit/include/hermit/tasks_types.h
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@ -91,6 +91,8 @@ typedef struct task {
uint64_t timeout;
/// starting time/tick of the task
uint64_t start_tick;
/// last TSC, when the task got the CPU
uint64_t last_tsc;
/// the userspace heap
vma_t* heap;
/// parent thread

24
hermit/kernel/tasks.c
View file

@ -54,8 +54,8 @@ extern atomic_int32_t cpu_online;
* A task's id will be its position in this array.
*/
static task_t task_table[MAX_TASKS] = { \
[0] = {0, TASK_IDLE, 0, NULL, NULL, NULL, TASK_DEFAULT_FLAGS, 0, 0, 0, NULL, 0, NULL, NULL, 0, 0, 0, NULL, FPU_STATE_INIT}, \
[1 ... MAX_TASKS-1] = {0, TASK_INVALID, 0, NULL, NULL, NULL, TASK_DEFAULT_FLAGS, 0, 0, 0, NULL, 0, NULL, NULL, 0, 0, 0, NULL, FPU_STATE_INIT}};
[0] = {0, TASK_IDLE, 0, NULL, NULL, NULL, TASK_DEFAULT_FLAGS, 0, 0, 0, 0, NULL, 0, NULL, NULL, 0, 0, 0, NULL, FPU_STATE_INIT}, \
[1 ... MAX_TASKS-1] = {0, TASK_INVALID, 0, NULL, NULL, NULL, TASK_DEFAULT_FLAGS, 0, 0, 0, 0, NULL, 0, NULL, NULL, 0, 0, 0, NULL, FPU_STATE_INIT}};
static spinlock_irqsave_t table_lock = SPINLOCK_IRQSAVE_INIT;
@ -200,8 +200,23 @@ void check_scheduling(void)
if (!is_irq_enabled())
return;
if (get_highest_priority() > per_core(current_task)->prio)
uint32_t prio = get_highest_priority();
task_t* curr_task = per_core(current_task);
if (prio > curr_task->prio) {
reschedule();
} else if (prio == curr_task->prio) {
// if a task is ready, check if the current task runs already one tick (one time slice)
// => reschedule to realize round robin
const uint64_t diff_cycles = get_rdtsc() - curr_task->last_tsc;
const uint64_t cpu_freq_hz = 1000000ULL * (uint64_t) get_cpu_frequency();
if (((diff_cycles * (uint64_t) TIMER_FREQ) / cpu_freq_hz) > 0) {
//kprintf("Time slice expired for task %d on core %d. New task has priority %u.\n", curr_task->id, CORE_ID, prio);
reschedule();
}
}
}
@ -495,6 +510,7 @@ int clone_task(tid_t* id, entry_point_t ep, void* arg, uint8_t prio)
task_table[i].prio = prio;
task_table[i].heap = curr_task->heap;
task_table[i].start_tick = get_clock_tick();
task_table[i].last_tsc = 0;
task_table[i].parent = curr_task->id;
task_table[i].tls_addr = curr_task->tls_addr;
task_table[i].tls_size = curr_task->tls_size;
@ -597,6 +613,7 @@ int create_task(tid_t* id, entry_point_t ep, void* arg, uint8_t prio, uint32_t c
task_table[i].prio = prio;
task_table[i].heap = NULL;
task_table[i].start_tick = get_clock_tick();
task_table[i].last_tsc = 0;
task_table[i].parent = 0;
task_table[i].ist_addr = ist;
task_table[i].tls_addr = 0;
@ -862,6 +879,7 @@ size_t** scheduler(void)
// finally make it the new current task
curr_task->status = TASK_RUNNING;
curr_task->last_tsc = get_rdtsc();
set_per_core(current_task, curr_task);
}