测试结果
我们日常多线程编程一定用到锁,那是不是锁不冲突就不耗时了呢?
如果锁耗时,那么具体会让性能减多少呢?
经过测试,结果如下:
运行10s如下:
不加锁:303637450
加锁:171365749
比值:1.8
也就是说不加锁比加锁快了近1倍。
PS:
本人的CPU型号是:CPU型号:Intel(R) Xeon(R) CPU E5-2630 0 @ 2.30GHz
因为每个循环都取时间,所以测试结果本身并不能代表CPU的性能。
虽然加锁会损耗性能,但是也不见得比你“存多分数据,频繁同步”会慢。
测试程序代码
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/timeb.h>
#include <sys/time.h>
#include <sys/stat.h>
#include <errno.h>
#include <string.h>
#include <iostream>
using namespace std;
typedef long long Int64;
static pthread_mutexattr_t sMutexAttr;
static pthread_once_t sMutexAttrInit = PTHREAD_ONCE_INIT;
void MutexAttrInit()
{
memset(&sMutexAttr, 0, sizeof(pthread_mutexattr_t));
pthread_mutexattr_init(&sMutexAttr);
}
class OSMutex
{
public:
OSMutex(){
(void)pthread_once(&sMutexAttrInit, MutexAttrInit);
(void)pthread_mutex_init(&fMutex, &sMutexAttr);
m_lockingthread = 0;
m_lockingtimes = 0;
}
~OSMutex(){
pthread_mutex_destroy(&fMutex);
}
void Lock(){
(void)pthread_mutex_lock(&fMutex);
}
void Unlock() {
pthread_mutex_unlock(&fMutex);
}
bool TryLock(){
int theErr = pthread_mutex_trylock(&fMutex);
if (theErr != 0)
{
return false;
}
}
private:
pthread_mutex_t fMutex;
pthread_t m_lockingthread;
int m_lockingtimes;
};
Int64 milliseconds()
{
struct timeval t;
struct timezone tz;
int theErr = ::gettimeofday(&t, &tz);
if(theErr < 0)
{
printf("gettimeofday failed\n");
}
Int64 tmp = (Int64)t.tv_sec * 1000 + t.tv_usec / 1000;
static Int64 last = 0x7FFFFFFFFFFFFFFFLL;
static int count = 0;
if((tmp - last)/10000 != 439)
{
last = tmp;
if(count != 0)
{
count = 0;
}
}
else
{
count++;
if(count > 10)
{
return last;
}
tmp = milliseconds();
}
return tmp;
}
int main()
{
Int64 before = milliseconds();
OSMutex mtx;
Int64 cnt = 0;
while (1) {
Int64 now = milliseconds();
if (now - before > 10000) {
break;
}
//mtx.Lock();
//mtx.Unlock();
cnt ++;
}
cout << cnt << endl;
return 0;
}
执行结果
[root@lh test]# g++ main26.cpp -o main26 -lpthread
[root@lh test]# ./main26
303460399
[root@lh test]# ./main26
303676424
[root@lh test]# ./main26
303775529
[root@lh test]# vim main26.cpp
#### 去掉Lock和Unlock的注释重新编译
[root@lh test]# g++ main26.cpp -o main26 -lpthread
[root@lh test]# ./main26
172484106
[root@lh test]# ./main26
168165401
[root@lh test]# ./main26
173447741
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