iOS中锁的研究

#define ITERATIONS (1024*1024*32)

int main(int argc, const char * argv[]) {

double then,now;

unsigned int i;

pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;

OSSpinLock spinLock = OS_SPINLOCK_INIT;

@autoreleasepool {

NSLock *lock = [NSLock new];

then = CFAbsoluteTimeGetCurrent();

for (i = 0; i < ITERATIONS; i ++) {

[lock lock];

[lock unlock];

}

now = CFAbsoluteTimeGetCurrent();

NSLog(@"NSLock time is      %f sec",now - then);

then = CFAbsoluteTimeGetCurrent();

for (i = 0; i < ITERATIONS; i ++) {

pthread_mutex_lock(&mutex);

pthread_mutex_unlock(&mutex);

}

now = CFAbsoluteTimeGetCurrent();

NSLog(@"pthread_mutex time is %f sec",now - then);

then = CFAbsoluteTimeGetCurrent();

for (i = 0; i < ITERATIONS; i ++) {

OSSpinLockLock(&spinLock);

OSSpinLockUnlock(&spinLock);

}

now = CFAbsoluteTimeGetCurrent();

NSLog(@"OSSpinLock time is    %f sec",now - then);

id obj = [NSObject new];

then = CFAbsoluteTimeGetCurrent();

for (i = 0; i < ITERATIONS; i ++) {

@synchronized(obj)

{

}

}

now = CFAbsoluteTimeGetCurrent();

NSLog(@"@synchronized time is  %f sec",now - then);

}

return 0;

}

得到的结果如下：