代码示例中三种类型：
1.pthread_mutex_t,互斥锁
2.__sync_add_and_fetch,GCC自带的原子锁
3.nolock,无锁方式
代码如下:
/********************************************************
> File Name: log_test.c
> Author: perrynzhou
> Mail: 715169549@qq.com
> Created Time: Fri 13 Jan 2017 05:00:46 PM HKT
********************************************************/
#include <stdio.h>
#include <stdint.h>
#include <pthread.h>
#include <stdbool.h>
#include <time.h>
#define MAX_THD_SIZE 2048
uint64_t max = 0;
uint64_t sum = 0;
pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER;
static void incrment_with_lock (int *data)
{
uint64_t i = 0;
uint64_t count = max / MAX_THD_SIZE;
for (; i < count; i++)
{
pthread_mutex_lock (&lock);
(*data)++;
pthread_mutex_unlock (&lock);
}
}
static void incrment_with_nolock (int *data)
{
uint64_t i = 0;
uint64_t count = max / MAX_THD_SIZE;
for (; i < count; i++)
{
(*data)++;
}
}
static void incrment_with_atomic (int *data)
{
uint64_t i = 0;
uint64_t count = max / MAX_THD_SIZE;
for (; i < count; i++)
{
__sync_add_and_fetch (data, 1);
}
}
bool is_digit (const char *s)
{
if (s == NULL)
{
return false;
}
while (*s != '\0')
{
if (isdigit (*(s++)) == 0)
{
return false;
}
}
return true;
}
int main (int argc, char *argv[])
{
if (argc != 2 || !is_digit (argv[1]))
{
fprintf (stdout, "usage: %s number \n", argv[0]);
return 0;
}
max = atoi (argv[1]);
clock_t start, end;
start = clock ();
pthread_t thd[MAX_THD_SIZE];
uint32_t i = 0;
#ifdef LOCK
for (; i < MAX_THD_SIZE; i++)
{
pthread_create (&thd[i], NULL, (void *) &incrment_with_lock, (void *) &sum);
}
for (i = 0; i < MAX_THD_SIZE; i++)
{
pthread_join (thd[i], NULL);
}
end = clock ();
fprintf (stdout, "sum = %d,incremnt_with_lock run time :%f s\n", sum, (double) (end - start) / CLOCKS_PER_SEC);
#endif
#ifdef ATOMIC
for (; i < MAX_THD_SIZE; i++)
{
pthread_create (&thd[i], NULL, (void *) &incrment_with_atomic, (void *) &sum);
}
for (i = 0; i < MAX_THD_SIZE; i++)
{
pthread_join (thd[i], NULL);
}
end = clock ();
fprintf (stdout, "sum = %d,incremnt_with_atomic run time :%f s\n", sum, (double) (end - start) / CLOCKS_PER_SEC);
#endif
#ifdef NOLOCK
for (; i < MAX_THD_SIZE; i++)
{
pthread_create (&thd[i], NULL, (void *) &incrment_with_nolock, (void *) &sum);
}
for (i = 0; i < MAX_THD_SIZE; i++)
{
pthread_join (thd[i], NULL);
}
end = clock ();
fprintf (stdout, "sum = %d,incremnt_with_nolock run time :%f s\n", sum, (double) (end - start) / CLOCKS_PER_SEC);
#endif
return 0;
}
测试结果：
结果描述
1.使用pthread_mutex_xxx类似的函数，针对多线程中操作一个变量，代价挺高，性能比较低。
2.不加锁这总方式，数据或错乱，但是性能是最佳的。
3.使用GCC原子锁,有一定的开销但是代价比使用pthread_mutex_xxx函数小。