pgfault.c

操作系统的一些有用的题目

#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <fcntl.h>
#include <signal.h>
#include <string.h>
#include <ctype.h>

#define PROCFILE "/proc/stat"
#define LINENUMBER 100

int fd;
int delay = 1;
int count = 1;
int realcount = 0;
int oldpgfault,pgfault;

void usage()
{
  printf("Usage: pgfault [delay [count]]\n");
  exit(1);
}

int getline(char *buf,int buflen)
{
  int i = 0;
  int ret;
  char c;

  while ((ret = read(fd,&c,1)) > 0 && c != '\n') {
    buf[i] = c;
    i++;
  }
  if (c == '\n')
    buf[i] = '\0';
  return i;
}

int readfile()
{
  int len,ret;
  int i = 0;
  char buf[LINENUMBER];
  char *p,*offset;
  
  if ((ret = lseek(fd,0,SEEK_SET)) < 0) {
    printf("lseek failed\n");
    exit(1);
  }
  while ((len = getline(buf,LINENUMBER)) > 0) {
    for (offset = buf; *offset != ' ' && *offset != '\t'; offset++);
    *offset = '\0';
    if (!strcmp(buf,"intr")) {
      *offset = ' ';
      while (*offset == ' ')
	offset++;
      for (i = 0; i < 16; i++) {
	p = offset;
	while (*offset != ' ')
	  offset++;
	while (*offset == ' ')
	  offset++;
      }
      *(offset-1) = '\0';
      ret = atoi(p);
      return ret;
    }
  }
  return -1;
}

void sig_handler(int signum)
{
  double rate;

  if (signum == SIGALRM) {
    if ((pgfault = readfile()) < 0) {
      printf("pgfault error\n");
      exit(1);
    } else {
      printf("virtual memory page fault: %d\n",pgfault);
      realcount++;
      if (realcount >= count) {
	rate = (double)(pgfault-oldpgfault)/(double)(delay*count);
	printf("%d\t%d/\t%d\n",pgfault,oldpgfault,delay*count);
	printf("pagefault rate %e\n",rate);
	exit(0);
      }
    }
  }
}

int main(int argc,char *argv[])
{
  struct itimerval timer;
  struct timeval interval,value;
  int val;

  switch (argc) {
  case 1:
    break;
  case 2:
    if ((val = atoi(*(++argv))) > 0)
      delay = val;
    else
      usage();
    break;
  case 3:
    if ((val = atoi(*(++argv))) > 0)
      delay = val;
    else
      usage();
    if ((val = atoi(*(++argv))) > 0)
      count = val;
    else
      usage();
   break;
  default:
    usage();
  }


  if ((fd = open(PROCFILE,O_RDONLY)) < 0) {
    printf("open file %s error",PROCFILE);
    exit(1);
  }

  oldpgfault = readfile();

  signal(SIGALRM,sig_handler);

  interval.tv_sec = delay;
  interval.tv_usec = 0;
  value.tv_sec = delay;
  value.tv_usec = 0;

  timer.it_interval = interval;
  timer.it_value = value;

  setitimer(ITIMER_REAL,&timer,NULL);
 
  while (1);

  close(fd);

  return 0;
}