tokuhirom's Blog

/proc/$$/smaps の読み方のメモ

http://unix.stackexchange.com/questions/33381/getting-information-about-a-process-memory-usage-from-proc-pid-smaps

#include <assert.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/types.h>
#include <unistd.h>
#include <sys/wait.h>

static void show_smaps(pid_t pid) {
  char cmd[1024];
  snprintf(cmd, sizeof(cmd), "cat /proc/%d/smaps > /tmp/out/%d", pid, pid);
  system(cmd);
}

int main() {
  system("rm -rf /tmp/out; mkdir -p /tmp/out");

  int i;
  char* buf = malloc(10*1024*1024);
  for (i=0; i<10*1024*1024; i++) {
    buf[i]=1;
  }

  // show smaps once.
  show_smaps(getpid());

  pid_t pid = fork();
  if (pid == 0) {
    sleep(1);
    show_smaps(getpid());
    for (i=0; i<5*1024*1024; i++) {
      buf[i]=2;
    }
    return 0;
  } else if (pid > 0) {
    sleep(2);
    show_smaps(getpid());
    printf("Parent pid: %d Child pid: %d\n", getpid(), pid);
    assert(kill(pid, SIGTERM) == 0);
    int status;
    assert(wait(&status) == pid);
    system("perl -E 'for my $f (</tmp/out/*>) { open my $fh, q!<!, $f; my %h; while (<$fh>) { $h{$1}+=$2 if /(Pss|Rss): +([0-9]+)/ }  say qq!$f:
 Rss:$h{Rss} Pss:$h{Pss}! }'");
    return 0;
  } else {
    perror("fork failed");
    return 1;
  }
}

[tokuhirom@dev2 pidstatd]$ gcc -Wall stat.c
[tokuhirom@dev2 pidstatd]$ ./a.out
Parent pid: 30910 Child pid: 30916
/tmp/out/30910: Rss:10736 Pss:10347
/tmp/out/30916: Rss:10452 Pss:5186