多线程 or 多进程 （实验1）

转自 http://stackoverflow.com/questions/556405/what-do-real-user-and-sys-mean-in-the-output-of-time1

• Real is wall clock time - time from start to finish of the call. This is all elapsed time including time slices used by other processes and time the process spends blocked (for example if it is waiting for I/O to complete).

• User is the amount of CPU time spent in user-mode code (outside the kernel) within the process. This is only actual CPU time used in executing the process. Other processes and time the process spends blocked do not count towards this figure.

• Sys is the amount of CPU time spent in the kernel within the process. This means executing CPU time spent in system calls within the kernel, as opposed to library code, which is still running in user-space. Like 'user', this is only CPU time used by the process. See below for a brief description of kernel mode (also known as 'supervisor' mode) and the system call mechanism.

User+Sys will tell you how much actual CPU time your process used.

转自 http://guishan.org/use-time-command-to-get-linux-command-execution-time-and-stopwatch/

需要注意的是，real并不等于user+sys的总和。real代表的是程序从开始到结束的全部时间，即使程序不占CPU也统计时间。而user+sys是程序占用CPU的总时间，因此real总是大于或者等于user+sys的。

time这个命令可以用来统计一个程序的执行时间，并且能详细到用户态执行时间和内核态执行时间。

实验环境：http://www.cnblogs.com/eavn/archive/2010/09/08/1821774.html

实验数据：

255\100		255\300		255\500		255\800
thread	process	thread	process	thread	process	thread	process
real0m0.784s	real0m0.782s	real0m2.653s	real0m2.537s	real0m4.397s	real0m4.609s	real0m6.795s	real0m6.770s
user0m0.004s	user0m0.024s	user0m0.000s	user0m0.072s	user0m0.000s	user0m0.144s	user0m0.000s	user0m0.196s
sys0m0.008s	sys0m0.140s	sys0m0.012s	sys0m0.204s	sys0m0.012s	sys0m0.472s	sys0m0.000s	sys0m0.484s
real0m0.780s	real0m0.775s	real0m2.516s	real0m2.491s	real0m4.252s	real0m4.311s	real0m6.921s	real0m6.993s
user0m0.000s	user0m0.032s	user0m0.004s	user0m0.068s	user0m0.004s	user0m0.128s	user0m0.000s	user0m0.180s
sys0m0.008s	sys0m0.116s	sys0m0.004s	sys0m0.232s	sys0m0.008s	sys0m0.408s	sys0m0.008s	sys0m0.536s
real0m0.784s	real0m0.784s	real0m2.526s	real0m2.505s	real0m4.269s	real0m4.356s	real0m7.159s	real0m6.862s
user0m0.000s	user0m0.036s	user0m0.000s	user0m0.048s	user0m0.000s	user0m0.148s	user0m0.004s	user0m0.180s
sys0m0.012s	sys0m0.120s	sys0m0.004s	sys0m0.228s	sys0m0.012s	sys0m0.376s	sys0m0.004s	sys0m0.464s
real0m0.757s	real0m0.783s	real0m2.495s	real0m2.504s	real0m4.253s	real0m4.253s	real0m6.895s	real0m6.906s
user0m0.000s	user0m0.028s	user0m0.004s	user0m0.068s	user0m0.000s	user0m0.136s	user0m0.004s	user0m0.168s
sys0m0.012s	sys0m0.132s	sys0m0.012s	sys0m0.224s	sys0m0.012s	sys0m0.428s	sys0m0.008s	sys0m0.548s
real0m0.793s	real0m0.792s	real0m2.495s	real0m2.579s	real0m4.182s	real0m4.246s	real0m6.939s	real0m6.964s
user0m0.000s	user0m0.036s	user0m0.004s	user0m0.108s	user0m0.004s	user0m0.160s	user0m0.000s	user0m0.208s
sys0m0.020s	sys0m0.112s	sys0m0.012s	sys0m0.224s	sys0m0.004s	sys0m0.408s	sys0m0.004s	sys0m0.536s
real0m0.780s	real0m0.793s	real0m2.539s	real0m2.532s	real0m4.321s	real0m4.223s	real0m6.844s	real0m6.940s
user0m0.004s	user0m0.052s	user0m0.000s	user0m0.052s	user0m0.000s	user0m0.140s	user0m0.000s	user0m0.180s
sys0m0.004s	sys0m0.144s	sys0m0.008s	sys0m0.256s	sys0m0.004s	sys0m0.392s	sys0m0.008s	sys0m0.464s
real0m0.807s	real0m0.777s	real0m2.517s	real0m2.484s	real0m4.182s	real0m4.209s	real0m7.196s	real0m6.932s
user0m0.000s	user0m0.036s	user0m0.004s	user0m0.080s	user0m0.004s	user0m0.128s	user0m0.000s	user0m0.172s
sys0m0.008s	sys0m0.112s	sys0m0.004s	sys0m0.196s	sys0m0.004s	sys0m0.372s	sys0m0.004s	sys0m0.512s
real0m0.788s	real0m0.797s	real0m2.484s	real0m2.485s	real0m4.241s	real0m5.371s	real0m6.804s	real0m6.961s
user0m0.000s	user0m0.024s	user0m0.000s	user0m0.092s	user0m0.000s	user0m0.140s	user0m0.000s	user0m0.208s
sys0m0.012s	sys0m0.136s	sys0m0.004s	sys0m0.260s	sys0m0.008s	sys0m0.400s	sys0m0.012s	sys0m0.480s
784.833333	785.166667	2514.333333	2508.5	4252.5	4332.333333	6926.666667	6927.333333
0.666667	31.5	2	71.5	1.333333	139	0.666667	185.166667
10	125.833333	7.333333	227.833333	8	401.5	6	501.666667

255\1000		255\5000		255\5000
thread	process	thread	process	thread	process
real0m8.496s	real0m8.961s	real0m50.289s	real0m51.965s	real1m30.752s	real1m31.121s
user0m0.008s	user0m0.240s	user0m1.704s	user0m1.408s	user0m2.052s	user0m2.568s
sys0m0.008s	sys0m0.804s	sys0m2.936s	sys0m3.392s	sys0m8.477s	sys0m6.216s
real0m8.460s	real0m8.578s	real0m44.868s	real0m44.689s	real1m30.542s	real1m30.769s
user0m0.000s	user0m0.336s	user0m1.636s	user0m1.316s	user0m2.132s	user0m2.532s
sys0m0.012s	sys0m0.664s	sys0m3.104s	sys0m3.232s	sys0m8.581s	sys0m6.344s
real0m8.493s	real0m8.450s	real0m44.490s	real0m45.209s	real1m30.483s	real1m31.582s
user0m0.004s	user0m0.304s	user0m0.992s	user0m1.412s	user0m2.000s	user0m2.420s
sys0m0.012s	sys0m0.740s	sys0m2.060s	sys0m3.600s	sys0m8.097s	sys0m6.112s
real0m8.442s	real0m8.420s	real0m43.916s	real0m48.919s	real1m31.136s	real1m30.916s
user0m0.004s	user0m0.268s	user0m1.200s	user0m1.332s	user0m2.460s	user0m2.520s
sys0m0.008s	sys0m0.724s	sys0m2.408s	sys0m3.512s	sys0m8.073s	sys0m6.532s
real0m8.575s	real0m8.450s	real0m45.639s	real0m47.608s	real1m30.305s	real1m31.100s
user0m0.000s	user0m0.268s	user0m1.232s	user0m1.384s	user0m1.500s	user0m2.460s
sys0m0.008s	sys0m0.740s	sys0m2.156s	sys0m3.468s	sys0m6.564s	sys0m6.256s
real0m8.533s	real0m8.469s	real0m43.383s	real0m46.837s	real1m13.056s	real1m31.788s
user0m0.000s	user0m0.292s	user0m1.572s	user0m1.284s	user0m1.620s	user0m2.648s
sys0m0.012s	sys0m0.740s	sys0m2.952s	sys0m3.464s	sys0m6.076s	sys0m6.516s
real0m8.430s	real0m8.427s	real0m42.469s	real0m55.889s	real1m18.466s	real1m31.126s
user0m0.004s	user0m0.272s	user0m1.544s	user0m1.324s	user0m1.228s	user0m2.320s
sys0m0.008s	sys0m0.756s	sys0m2.944s	sys0m3.448s	sys0m5.712s	sys0m5.596s
real0m8.642s	real0m8.461s	real0m44.512s	real1m0.179s	real1m18.096s	real1m30.226s
user0m0.004s	user0m0.228s	user0m1.644s	user0m1.224s	user0m1.416s	user0m2.272s
sys0m0.008s	sys0m0.780s	sys0m3.140s	sys0m3.580s	sys0m5.812s	sys0m5.752s
8499.5	8471.666667	44467.833333	49404.166667	86440.333333	91102
2.666667	273.5	1470.666667	1341	1786.5	2469.5
9.333333	746	2749.333333	3476.666667	7182.833333	6199.166667

 

	thread	process
255\100	784.833333	785.166667
	0.666667	31.5
	10	125.833333
255\300	2514.333333	2508.5
	2	71.5
	7.333333	227.833333
255\500	4252.5	4332.333333
	1.333333	139
	8	401.5
255\800	6926.666667	6927.333333
	0.666667	185.166667
	6	501.666667
255\1000	8499.5	8471.666667
	2.666667	273.5
	9.333333	746
255\5000	44467.833333	49404.166667
	1470.666667	1341
	2749.333333	3476.666667
255\5000	86440.333333	91102
	1786.5	2469.5
	7182.833333	6199.166667

上述实验数据第一行为P_NUMBER\COUNT的值，每组实验做8次，然后去掉最高值、最低值，再取平均值，为最后三行

从平均值可看出real数据相差不大，相差较大的是user和sys，而根据前文描述用户关心的为real，因此相差不是很大，对linux系统的线程进程实现了解不是很深入，因此对其中的原因不是很清楚，望大牛给予指点

实验中最好是一个实验一个实验慢慢跑，如果是几个实验一起跑可能会有重大偏差

对于给的试验结果不太符合：任务量较大时,多进程比多线程效率高;而完成的任务量较小时,多线程比多进程要快，重复打印 600 次时,多进程与多线程所耗费的时间相同

而且可以说我的结论恰恰相反：任务量较小时，多进程效率较好，任务量较小时，多线程效率较好，这个分界点暂时没法确定

这个原因可能是因为系统不一样；我的求平均值假设不对；。。。

 

附件求平均值程序

输入data

real    0m6.770s
user    0m0.196s
sys    0m0.484s

real    0m6.993s
user    0m0.180s
sys    0m0.536s

real    0m6.862s
user    0m0.180s
sys    0m0.464s

real    0m6.906s
user    0m0.168s
sys    0m0.548s

real    0m6.964s
user    0m0.208s
sys    0m0.536s

real    0m6.940s
user    0m0.180s
sys    0m0.464s

real    0m6.932s
user    0m0.172s
sys    0m0.512s

real    0m6.961s
user    0m0.208s
sys    0m0.480s

程序

#include <stdlib.h>
#include <stdio.h>
#include <string.h>

#define MAXSZSIZE 32
#define MAXNUM 64

static int cmp(const void *p1, const void *p2)
{
    return *((long*)p1) > *((long*)p2);
}

int main()
{
    char sz_input[MAXSZSIZE];
    char sz_filename[MAXSZSIZE]="data";

    long l_real[MAXNUM],l_user[MAXNUM],l_sys[MAXNUM];
    long *lp=NULL;

    long long_min=0;
    double df_second=0;
    
    long l_real_total=0,l_user_total=0,l_sys_total=0;
    double df_real_avg=0,df_user_avg=0,df_sys_avg=0;

    FILE *f_handle=NULL;
    int int_flag=0,int_index=0;

    memset (l_real, 0 ,sizeof(l_real));
    memset (l_user, 0 ,sizeof(l_user));
    memset (l_sys, 0 ,sizeof(l_sys));

    f_handle=fopen (sz_filename,"r");

    if (f_handle==NULL)
    {
        perror("can not open file:");
        return (1);
    }
    
    while (fscanf (f_handle,"%s",sz_input) !=EOF )
    {        
        if (strcmp(sz_input,"real")==0)
        {
            lp = l_real;
        }
        else if (strcmp(sz_input,"user")==0)
        {
            lp = l_user;
        }
        else if (strcmp(sz_input,"sys")==0)
        {
            lp = l_sys;
        }
        else 
        {
            continue;
        }
    
        fscanf (f_handle,"%ld%c%lf%c",&long_min,&sz_input[0],&df_second,&sz_input[1]);

        //printf ("%ld %c %f %c\n", long_min, sz_input[0], df_second, sz_input[1]);
        //exit (1);
        
        *lp = (*lp) + 1;

        
        *(lp+*lp) = (long) ((long_min*60+df_second)*1000);
    }

    for (int_index=1; int_index<=l_real[0]; int_index++)
        printf ("%ld\t%ld\t%ld\n",l_real[int_index],l_user[int_index],l_sys[int_index]);

    puts("\n");
    qsort(l_real+1,*l_real,sizeof(long),cmp);
    qsort(l_user+1,*l_user,sizeof(long),cmp);
    qsort(l_sys+1,*l_sys,sizeof(long),cmp);

    for (int_index=1; int_index<=l_real[0]; int_index++)
        printf ("%ld\t%ld\t%ld\n",l_real[int_index],l_user[int_index],l_sys[int_index]);

    puts("\n");
    l_real_total = 0;
    l_user_total = 0;
    l_sys_total = 0;
    for (int_index=2; int_index<l_real[0]; int_index++)
    {
        l_real_total += l_real[int_index];
        l_user_total += l_user[int_index];
        l_sys_total += l_sys[int_index];
    }

    df_real_avg = l_real_total*1.0 / (l_real[0]-2);
    df_user_avg = l_user_total*1.0 / (l_user[0]-2);
    df_sys_avg = l_sys_total*1.0 / (l_sys[0]-2);

    printf ("%lf\n%lf\n%lf\n", df_real_avg,df_user_avg,df_sys_avg);

    return 0;
}