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Wrote a benchmark for measuring the context switch time.

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This commit is contained in:
Jacek Galowicz 2012-04-15 19:40:51 +02:00
parent 0984eb593f
commit 9b36a72f5f
2 changed files with 59 additions and 16 deletions
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72
apps/tests.c
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@ -301,22 +301,65 @@ static int pi(void* arg)
return 0;
}
static int measure_ctx_switch(void)
{
uint64_t max = 0;
uint64_t start, t1, t2;
uint64_t freq = get_cpu_frequency();
#define REPS 10000
start = t1 = rdtsc();
do {
asm volatile ("cpuid");
t2 = rdtsc();
if (t2 - t1 > max)
max = t2 - t1;
t1 = t2;
} while(t2-start < 10*freq);
volatile uint64_t t1, t2;
volatile int stop = !!0;
volatile int sid = 0;
static int measure_ctx_switch(void* arg)
{
int id = !!(int)arg;
int oid = !id;
uint64_t freq = get_cpu_frequency() *1000 *1000;
uint64_t diff, min = (uint64_t)-1, max = 0, avg = 0;
int i;
uint32_t a=0,b,c,d;
// Size of a timeslice in ticks
uint64_t timeslice = freq / TIMER_FREQ;
kprintf("ID: %d, ", id);
#ifdef SW_TASK_SWITCH
kprintf("Measuring SW task switch.\n");
#else
kprintf("Measuring HW task switch.\n");
#endif
for (i=0; i < REPS && stop == 0; i++) {
while(id == sid && stop == 0) {
t2 = rdtsc();
cpuid(0,&a,&b,&c,&d);
}
cpuid(0,&a,&b,&c,&d);
diff = rdtsc() -t2;
// The last measurement is garbage
if (stop) break;
// The first ones are garbage, too
if (i < 5) goto next_try;
if (diff >= timeslice) {
i--;
goto next_try;
}
kprintf("%i: diff= %llu, i= %i\n", id, diff, i);
if (diff > max) max = diff;
if (diff < min) min = diff;
avg += diff;
next_try:
sid = id;
}
avg /= i-5;
stop = 1;
kprintf("maximum gap: %llu ticks\n", max);
kprintf("minimum gap: %llu ticks\n", min);
kprintf("average gap: %llu ticks\n", avg);
kprintf("Timeslice size: %llu ticks\n", timeslice);
return 0;
}
@ -332,7 +375,8 @@ int test_init(void)
sem_init(&consuming, 0);
mailbox_int32_init(&mbox);
create_kernel_task(NULL, measure_ctx_switch, NULL, NORMAL_PRIO);
create_kernel_task(NULL, measure_ctx_switch, (int)0, NORMAL_PRIO);
create_kernel_task(NULL, measure_ctx_switch, (int)1, NORMAL_PRIO);
//create_kernel_task(NULL, foo, "Hello from foo1", NORMAL_PRIO);
//create_kernel_task(NULL, foo, "Hello from foo2", NORMAL_PRIO);
//create_kernel_task(NULL, join_test, NULL, NORMAL_PRIO);

3
kernel/tasks.c
View file

@ -1378,8 +1378,7 @@ get_task_out:
orig_task->flags &= ~TASK_FPU_USED;
}
//kprintf("schedule from %u to %u with prio %u on core %u\n",
// orig_task->id, curr_task->id, (uint32_t)curr_task->prio, CORE_ID);
//kprintf("schedule from %u to %u with prio %u on core %u\n", orig_task->id, curr_task->id, (uint32_t)curr_task->prio, CORE_ID);
#ifndef SW_TASK_SWITCH
switch_task(curr_task->id);
#endif