c++ - How to use boost to track real time instead of user+sys? -

I am using boost :: timer to make a block of my code I run the code with a thread:

  $ time ./runfoo 1 2.08s real 0m2.086s user 0m1.611s sys 0m0.475s   
 The output of  2.08   t.elapsed ()  is.  
 However, if I run the code with 4 threads:  
  $ time. / Runfoo 4 has gone 2.47s real 0m1.022s user 0m1.834s sys 0m0.628s   
 It seems that tracking user + sys time is not real time.  
 How can I track it in real time? I am using Boost 1.46. To be more specific, the timer is in the main thread, which just calls a function that ends using multiple threads.  
 Edit: The related source looks like this:  
  Promotion :: asio :: io_service ios; Promotion: Thread_Group pool; Boost :: asio :: io_service :: Job work (ios); Pool.create_thread (boost :: bind (and boost :: aso :: io_service :: runs, & ioService)); Pool.create_thread (boost :: bind (and boost :: aso :: io_service :: runs, & ioService)); Pool.create_thread (boost :: bind (and boost :: aso :: io_service :: runs, & ioService)); Pool.create_thread (boost :: bind (and boost :: aso :: io_service :: runs, & ioService)); (Promotion: Timer T; function_which_posts_to_ios (IOS); Printf (""% .2fs taken \ n ", t.elapsed ();}   
 I hope the form of which output In order to print the program, I should look at the second run  instead of "code 1.02s" to  "taken 2.47s"  as  1.02s  The actual amount of seconds passed was in the form.   
 
 
 It appears that you  elapsed  )  were not consistent in platforms, others And some CPU time-time clock time. In this,  has passed ()  method gives a structure that is genuine, user and specific member for system time.  
 If you can not use version 2 API, you can use  boost :: posix_time  instead of measuring the time of the clock.   < / Html>