问statm不报告更新的VmSize

EN

#include <iostream>
#include <fstream>

void print_mem(){
  std::ifstream proc_stream("/proc/self/statm");
  long long VmSize = 0, VmRSS = 0, Share = 0;
  proc_stream >> VmSize >> VmRSS >> Share;
  proc_stream.close();
  std::cout << VmSize << " " << VmRSS << std::endl;
}

struct C{
    int a[256];
};

int main(){
    print_mem();// first call
    C* c = new C;
    print_mem();// second call
    return 0;
}