Why running std::thread with empty function spend a lot of memory

I wrote a simple program which should run two threads, sort small array (~4096 Byte) and write into an output file. Input data contain in the one big file (~4Gb). Computer has 128MB memory. I found that running just empty main function use 14MB memory. If run std::thread with empty function application start to use ~8MB per thread. BUT if i make just one dynamic memory allocation program starts to use approximately 64Mb per thread. I don't understand what can spend so much memory. How can I control this size? And how allocate dynamic memory to minimize some system default allocation?

• System: Ubuntu 14.04.3
• Compiler: gcc 4.8.4

• Compiler option:'-std=c++11 -O3 -pthread'

• This is a code example

  void dummy(void)
  {
      std::vector<unsigned int> g(1);
      int i = 0;
      while( i<500000000)
      {
          ++i;
      }
  }
  
  int main(void)
  {
      std::thread t1(&dummy);
      std::thread t2(&dummy);
      std::thread t3(&dummy);
      t1.join();
      t2.join();
      t3.join();
      return 0;
  }