gprof profiler не печатает сводку времени

Я создал простую программу:

#include <unistd.h>

void ssleep(unsigned int s)
{
  usleep(1000000*s);
}

int main(int, char**)
{
  ssleep(1);
}

После этих команд:

sch@sch-K52F:~/test$ g++ -pedantic -Wall main.cpp -pg
sch@sch-K52F:~/test$ ./a.out 
sch@sch-K52F:~/test$ gprof -b a.out > profile

Я получаю профиль без сводки времени:

  %   cumulative   self              self     total           
 time   seconds   seconds    calls  Ts/call  Ts/call  name    
  0.00      0.00     0.00        1     0.00     0.00  ssleep(unsigned int)

Такая же ситуация с любым другим кодом. Я что-то упускаю?

Моя система:

sch@sch-K52F:~/test$ uname -a
Linux sch-K52F 3.2.0-45-generic-pae #70-Ubuntu SMP Wed May 29 20:31:05 UTC 2013 i686 i686 i386 GNU/Linux
sch@sch-K52F:~/test$ gprof -v
GNU gprof (GNU Binutils for Ubuntu) 2.22
Based on BSD gprof, copyright 1983 Regents of the University of California.
This program is free software.  This program has absolutely no warranty.

Спасибо

редактировать 1)

другой пример:

 time   seconds   seconds    calls  Ts/call  Ts/call  name
  0.00      0.00     0.00     1482     0.00     0.00  std::_Iter_base<unsigned char*, false>::_S_base(unsigned char*)
  0.00      0.00     0.00     1482     0.00     0.00  std::_Niter_base<unsigned char*>::iterator_type std::__niter_base<unsigned char*>(unsigned char*)
  0.00      0.00     0.00     1247     0.00     0.00  std::_Vector_base<unsigned char, std::allocator<unsigned char> >::_M_get_Tp_allocator()
  0.00      0.00     0.00      988     0.00     0.00  __gnu_cxx::__normal_iterator<unsigned char*, std::vector<unsigned char, std::allocator<unsigned char> > >::base() const
  0.00      0.00     0.00      988     0.00     0.00  std::move_iterator<unsigned char*>::base() const
  0.00      0.00     0.00      988     0.00     0.00  std::vector<unsigned char, std::allocator<unsigned char> >::size() const
  0.00      0.00     0.00      988     0.00     0.00  std::_Iter_base<std::move_iterator<unsigned char*>, true>::_S_base(std::move_iterator<unsigned char*>)
  0.00      0.00     0.00      988     0.00     0.00  std::move_iterator<unsigned char*>::move_iterator(unsigned char*)
  0.00      0.00     0.00      988     0.00     0.00  std::_Miter_base<std::move_iterator<unsigned char*> >::iterator_type std::__miter_base<std::move_iterator<unsigned char*> >(std::move_iterator<unsigned char*>)
  0.00      0.00     0.00      988     0.00     0.00  std::move_iterator<unsigned char*> std::make_move_iterator<unsigned char*>(unsigned char* const&)
  0.00      0.00     0.00      741     0.00     0.00  __gnu_cxx::new_allocator<unsigned char>::max_size() const
  0.00      0.00     0.00      555     0.00     0.00  operator new(unsigned int, void*)
  0.00      0.00     0.00      541     0.00     0.00  void std::_Destroy_aux<true>::__destroy<unsigned char*>(unsigned char*, unsigned char*)
  0.00      0.00     0.00      541     0.00     0.00  std::_Vector_base<unsigned char, std::allocator<unsigned char> >::_M_deallocate(unsigned char*, unsigned int)
  0.00      0.00     0.00      541     0.00     0.00  void std::_Destroy<unsigned char*>(unsigned char*, unsigned char*)

Я всегда получаю нулевое время для любого кода, любой функции;/