[SOLVED] [c / sysinfo()] explication about struct sysinfo

[pknzeta]

hi,
I need some precisions about a field of struct sysinfo (passed to sysinfo() ); well. I wrote this function;

void get_sys_informations(sys_informations * sys_info)
{
   if(sysinfo(sys_info)==0)
   {
      printf("%ld\n",sys_info->loads[0]);

      printf(sys_info_format,
         sys_info->uptime,
         sys_info->loads[0]/1000,
         sys_info->loads[1]/1000,
         sys_info->loads[2]/1000,
         (sys_info->totalram - sys_info->freeram)/MEGABYTE,
         (sys_info->totalram)/MEGABYTE,
         (sys_info->sharedram)/MEGABYTE,
         (sys_info->bufferram)/MEGABYTE,
         (sys_info->totalswap - sys_info->freeswap)/MEGABYTE,
         (sys_info->totalswap)/MEGABYTE,
         sys_info->procs,
         (sys_info->totalhigh - sys_info->freehigh)/MEGABYTE,
         (sys_info->totalhigh)/MEGABYTE,
         sys_info->mem_unit
      );
   }
   else
   {
      printf("[EE] Can't get system informations.\n");
      exit(EXIT_FAILURE);
   }
}

As you can see, I divided sys_info->loads by 1000 as I thinks that will tell me the average cpu usage in %. but I learned that was wrong. anyway... Now, I know that it's the computer load average as described here. My question is, how do i interpret the sysinfo->loads values. man page is not really helpful about this. here is a little exemple about output of this function;
$ cat /proc/loadavg; ./test

0.05 0.06 0.08 2/158 14502  
3040
Uptime: 59320 seconds
Load averages:
1 minute: 3% 5 minutes: 3% 15 minutes: 5%
memory: 1490MB used of 1504MB
Shared memory: 0MB
Memory used by buffers: 27MB
Swap: 0MB used of 996MB
Process count: 158
High Mem: 0MB used of 0MB
Size of a memory block: 1 byte

Help me please.
Sorry if I misspelled some words, I'm not a native speaker. (french)

[wje_lf]

Sample code:

#include <sys/sysinfo.h>
#include <stdio.h>
#include <stdlib.h>
#include <time.h>

int main(void)
{
  volatile time_t time1;
  volatile time_t time2;

  float           fav[3];
  float           shiftfloat;

  struct sysinfo  the_info;

  time1=time(NULL);

  for(;;)
  {
    time2=time(NULL);

    if(time2>=time1+5)
    {
      break;   /* <--------- */
    }
  }

  shiftfloat=(float)(1<<SI_LOAD_SHIFT);

  if(sysinfo(&the_info))
  {
    perror("sysinfo()");

    exit(1);
  }

  fav[0]=((float)the_info.loads[0])/shiftfloat;
  fav[1]=((float)the_info.loads[1])/shiftfloat;
  fav[2]=((float)the_info.loads[2])/shiftfloat;

  printf("SI_LOAD_SHIFT %d\n",SI_LOAD_SHIFT);
  printf("%f %f %f\n",fav[0],fav[1],fav[2]);

  system("uptime");

  return 0;

} /* main() */

Hope this helps.

[pknzeta]

that helped, thank you.

can I have a little explication of this:

float shiftfloat=(1<<SI_LOAD_SHIFT);

I'm new to C and i don't really understand what is it.

[wje_lf]

I'm new to C

Almost all of the elements of the statement you quote can be understood if you have basic knowlege of C. I don't have time to write a C tutorial at this point, but several people have done so. To find their tutorials, scroogle this:

C tutorial

But I'll help you with one item which won't be obvious from the C tutorial, ok? :)

One statement in the program is

#include <sys/sysinfo.h>

That file is found at /usr/include/sys/sysinfo.h. In that file is this statement:

#include <linux/kernel.h>

That file is found at /usr/include/linux/kernel.h. In that file is this statement:

#define SI_LOAD_SHIFT   16

Just so you know.