linux中监视系统运行信息，需要研究/proc下的一些信息，/proc/stat/给出了cpu的运行信息，先来分析一下
[
work@builder
~]$ cat /proc/stat
cpu 432661 13295 86656 422145968 171474 233 5346
cpu0 123075 2462 23494 105543694 16586 0 4615
cpu1 111917 4124 23858 105503820 69697 123 371
cpu2 103164 3554 21530 105521167 64032 106 334
cpu3 94504 3153 17772 105577285 21158 4 24
intr 1065711094 1057275779 92 0 6 6 0 4 0 3527 0 0 0 70 0 20 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 7376958 0 0 0 0 0 0 0 1054602 0 0 0 0 0 0 0 30 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
ctxt 19067887
btime 1139187531
processes 270014
procs_running 1
procs_blocked 0
输出解释
CPU 以及CPU0、CPU1、CPU2、CPU3每行的每个参数意思（以第一行为例）为：
参数 解释
user (432661) 从系统启动开始累计到当前时刻，用户态的CPU时间（单位：jiffies） ，不包含 nice值为负进程。1jiffies=0.01秒
nice (13295) 从系统启动开始累计到当前时刻，nice值为负的进程所占用的CPU时间（单位：jiffies）
system (86656) 从系统启动开始累计到当前时刻，核心时间（单位：jiffies）
idle (422145968) 从系统启动开始累计到当前时刻，除硬盘IO等待时间以外其它等待时间（单位：jiffies）
iowait (171474) 从系统启动开始累计到当前时刻，硬盘IO等待时间（单位：jiffies） ，
irq (233) 从系统启动开始累计到当前时刻，硬中断时间（单位：jiffies）
softirq (5346) 从系统启动开始累计到当前时刻，软中断时间（单位：jiffies）
CPU时间=user+system+nice+idle+iowait+irq+softirq
“intr”这行给出中断的信息，第一个为自系统启动以来，发生的所有的中断的次数；然后每个数对应一个特定的中断自系统启动以来所发生的次数。
“ctxt”给出了自系统启动以来CPU发生的上下文交换的次数。
“btime”给出了从系统启动到现在为止的时间，单位为秒。
“processes (total_forks) 自系统启动以来所创建的任务的个数目。
“procs_running”：当前运行队列的任务的数目。
“procs_blocked”：当前被阻塞的任务的数目。
通过两次读取/proc/stat文件，计算出cpu的busy和idle时间差。
代码只是简单的获取出CPU使用率，如果用到系统里，还是要用线程的。
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <stdarg.h>
#include <errno.h>
#define STATES_line2x4
“%s\03” \
” %#5.1f%% \02user,\03 %#5.1f%% \02system,\03 %#5.1f%% \02nice,\03 %#5.1f%% \02idle\03\n”
static const char *States_fmts = STATES_line2x4;
//Total number of CPU
static int Cpu_tot;
// These typedefs attempt to ensure consistent ‘ticks’ handling
typedef unsigned long long TIC_t;
// This structure stores a frame’s cpu tics used in history
// calculations.
It exists primarily for SMP support but serves
// all environments.
typedef struct CPU_t {
TIC_t u, n, s, i, w, x, y;
// as represented in /proc/stat
TIC_t u_sav, s_sav, n_sav, i_sav, w_sav, x_sav, y_sav; // in the order of our display
unsigned id;
// the CPU ID number
} CPU_t;
// This routine simply formats whatever the caller wants and
// returns a pointer to the resulting ‘const char’ string…
static const char *fmtmk (const char *fmts, …)
{
static char buf[2048];
// with help stuff, our buffer
va_list va;
// requirements exceed 1k
va_start(va, fmts);
vsnprintf(buf, sizeof(buf), fmts, va);
va_end(va);
return (const char *)buf;
}
static CPU_t *cpus_refresh (CPU_t *cpus)
{
static FILE *fp = NULL;
int i;
int num;
// enough for a /proc/stat CPU line (not the intr line)
char buf[256+64];
if (!fp) {
if (!(fp = fopen(“/proc/stat”, “r”)))
printf(“Failed /proc/stat open: %s”, strerror(errno));
//cpus = calloc(1, (1 + Cpu_tot) * sizeof(CPU_t));
cpus = (CPU_t *)malloc((1 + Cpu_tot) * sizeof(CPU_t));
memset(cpus, ‘\0’, (1 + Cpu_tot) * sizeof(CPU_t));
}
rewind(fp);
fflush(fp);
// first value the last slot with the cpu summary line
if (!fgets(buf, sizeof(buf), fp)) printf(“failed /proc/stat read\n”);
cpus[Cpu_tot].x = 0;
// FIXME: can’t tell by kernel version number
cpus[Cpu_tot].y = 0;
// FIXME: can’t tell by kernel version number
num = sscanf(buf, “cpu %Lu %Lu %Lu %Lu %Lu %Lu %Lu”,
&cpus[Cpu_tot].u,
&cpus[Cpu_tot].n,
&cpus[Cpu_tot].s,
&cpus[Cpu_tot].i,
&cpus[Cpu_tot].w,
&cpus[Cpu_tot].x,
&cpus[Cpu_tot].y
);
if (num < 4)
printf(“failed /proc/stat read\n”);
// and just in case we’re 2.2.xx compiled without SMP support…
if (Cpu_tot == 1) {
cpus[1].id = 0;
memcpy(cpus, &cpus[1], sizeof(CPU_t));
}
// now value each separate cpu’s tics
for (i = 0; 1 < Cpu_tot && i < Cpu_tot; i++) {
if (!fgets(buf, sizeof(buf), fp)) printf(“failed /proc/stat read\n”);
cpus[i].x = 0;
// FIXME: can’t tell by kernel version number
cpus[i].y = 0;
// FIXME: can’t tell by kernel version number
num = sscanf(buf, “cpu%u %Lu %Lu %Lu %Lu %Lu %Lu %Lu”,
&cpus[i].id,
&cpus[i].u, &cpus[i].n, &cpus[i].s, &cpus[i].i, &cpus[i].w, &cpus[i].x, &cpus[i].y
);
if (num < 4)
printf(“failed /proc/stat read\n”);
}
return cpus;
}
static void summaryhlp (CPU_t *cpu, const char *pfx)
{
// we’ll trim to zero if we get negative time ticks,
// which has happened with some SMP kernels (pre-2.4?)
#define TRIMz(x)
((tz = (long long)(x)) < 0 ? 0 : tz)
long long u_frme, s_frme, n_frme, i_frme, w_frme, x_frme, y_frme, tot_frme, tz;
float scale;
if(cpu == NULL){
printf(”
NULL@\n
“);
return;
}
printf(“u = %Lu, u_sav = %Lu\n”, cpu->u, cpu->u_sav);
u_frme = cpu->u – cpu->u_sav;
s_frme = cpu->s – cpu->s_sav;
n_frme = cpu->n – cpu->n_sav;
i_frme = TRIMz(cpu->i – cpu->i_sav);
w_frme = cpu->w – cpu->w_sav;
x_frme = cpu->x – cpu->x_sav;
y_frme = cpu->y – cpu->y_sav;
tot_frme = u_frme + s_frme + n_frme + i_frme + w_frme + x_frme + y_frme;
if (tot_frme < 1) tot_frme = 1;
scale = 100.0 / (float)tot_frme;
printf(“scale = %0.5f\n”, scale);
// display some kinda’ cpu state percentages
// (who or what is explained by the passed prefix)
printf(States_fmts,
pfx,
(float)u_frme * scale,
(float)s_frme * scale,
(float)n_frme * scale,
(float)i_frme * scale,
(float)w_frme * scale,
(float)x_frme * scale,
(float)y_frme * scale
);
// remember for next time around
cpu->u_sav = cpu->u;
cpu->s_sav = cpu->s;
cpu->n_sav = cpu->n;
cpu->i_sav = cpu->i;
cpu->w_sav = cpu->w;
cpu->x_sav = cpu->x;
cpu->y_sav = cpu->y;
#undef TRIMz
}
int main()
{
static CPU_t * smpcpu = NULL;
for(;;){
Cpu_tot = sysconf(_SC_NPROCESSORS_ONLN);
printf(“CPU number: %ld\n”, Cpu_tot);
smpcpu = cpus_refresh(smpcpu);
summaryhlp(&smpcpu[Cpu_tot], “Cpu(s):”);
printf(“\n”);
sleep(3);
smpcpu = cpus_refresh(smpcpu);
summaryhlp(&smpcpu[Cpu_tot], “Cpu(s):”);
printf(“++++++++++++++++++++++++++\n”);
}
return 0;
}
转自：
http://blog.163.com/sxs_solo/blog/static/2633338201011129811606/