fork_memory_usage.cc

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

#define A1 (1024 * 1024 * 200)
#define A2_PARENT (1024 * 1024 * 300)
#define A2_CHILD (1024 * 1024 * 500)

int main() {
  char* a1;
  char* a2;
  pid_t pid;

  a1 = (char *)malloc(A1);
  for (int i = 0; i < A1; ++i) {
    *(a1 + i) = 0xca;
  }

  pid = fork();
  if (pid > 0) {  // parent
    int status;
    a2 = (char *)malloc(A2_PARENT);
    for (int i = 0; i < A2_PARENT; ++i) {
      *(a2 + i) = 0xfe;
    }
    waitpid(pid, &status, 0);
  } else if (pid == 0) {  // child
    a2 = (char *)malloc(A2_CHILD);
    for (int i = 0; i < A2_CHILD; ++i) {
      *(a2 + i) = 0xba;
    }
    sleep(6000);
  }
  return 0;
}

ps.txt

USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
114584   24702  8.7  0.7 516168 512224 pts/9   S+   13:15   0:01 ./fork_memory_usage
114584   24703 11.0  1.0 720968 716760 pts/9   S+   13:15   0:01 ./fork_memory_usage

statm.child.txt

180242 179190 7 1 0 179247 0

statm.parent.txt

129042 128056 86 1 0 128047 0

Total RSS of them without double-counting is 1049071616 bytes.