如何写个shell脚本获取上下文切换的开销,之前提了个问题在描述中，貌似没人注意？
#include <stdlib.h>
#include <stdint.h>
#include <stdio.h>
#include <pthread.h>
#include <sys/time.h>
#include <unistd.h>
uint32_t COUNTER;
pthread_mutex_t LOCK;
pthread_mutex_t START;
pthread_cond_t CONDITION;
void * threads (
void * unused
) {
// Wait till we may fire away
pthread_mutex_lock(&START);
pthread_mutex_unlock(&START);
pthread_mutex_lock(&LOCK);
// If I'm not the first thread, the other thread is already waiting on
// the condition, thus Ihave to wake it up first, otherwise we'll deadlock
if (COUNTER > 0) {
pthread_cond_signal(&CONDITION);
}
for (;;) {
COUNTER++;
pthread_cond_wait(&CONDITION, &LOCK);
// Always wake up the other thread before processing. The other
// thread will not be able to do anything as long as I don't go
// back to sleep first.
pthread_cond_signal(&CONDITION);
}
pthread_mutex_unlock(&LOCK); //To unlock
}
int64_t timeInMS ()
{
struct timeval t;
gettimeofday(&t, NULL);
return (
(int64_t)t.tv_sec * 1000 +
(int64_t)t.tv_usec / 1000
);
}
int main (
int argc,
char ** argv
) {
int64_t start;
pthread_t t1;
pthread_t t2;
int64_t myTime;
pthread_mutex_init(&LOCK, NULL);
pthread_mutex_init(&START, NULL);
pthread_cond_init(&CONDITION, NULL);
pthread_mutex_lock(&START);
COUNTER = 0;
pthread_create(&t1, NULL, threads, NULL);
pthread_create(&t2, NULL, threads, NULL);
pthread_detach(t1);
pthread_detach(t2);
// Get start time and fire away
myTime = timeInMS();
pthread_mutex_unlock(&START);
// Wait for about a second
sleep(1);
// Stop both threads
pthread_mutex_lock(&LOCK);
// Find out how much time has really passed. sleep won't guarantee me that
// I sleep exactly one second, I might sleep longer since even after being
// woken up, it can take some time before I gain back CPU time. Further
// some more time might have passed before I obtained the lock!
myTime = timeInMS() - myTime;
// Correct the number of thread switches accordingly
COUNTER = (uint32_t)(((uint64_t)COUNTER * 1000) / myTime);
printf("Number of thread switches in about one second was %u\n", COUNTER);
return 0;
}