ceph/src/boost/libs/fiber/performance/thread/overhead_future.cpp

   1
   2 //          Copyright Oliver Kowalke 2009.
   3 // Distributed under the Boost Software License, Version 1.0.
   4 //    (See accompanying file LICENSE_1_0.txt or copy at
   5 //          http://www.boost.org/LICENSE_1_0.txt)
   6
   7 #include <cstdlib>
   8 #include <future>
   9 #include <iostream>
  10 #include <stdexcept>
  11 #include <thread>
  12
  13 #include <boost/cstdint.hpp>
  14 #include <boost/preprocessor.hpp>
  15
  16 #include "../clock.hpp"
  17
  18 #ifndef JOBS
  19 #define JOBS BOOST_PP_LIMIT_REPEAT
  20 #endif
  21
  22 #define WAIT(z, n, _) \
  23 { \
  24     std::packaged_task< void() > pt( worker); \
  25     std::future< void > f( pt.get_future() ); \
  26     std::thread( std::move( pt) ).detach(); \
  27     time_point_type start( clock_type::now() ); \
  28     f.wait(); \
  29     duration_type total = clock_type::now() - start; \
  30     total -= overhead; \
  31     result += total; \
  32 }
  33
  34 void worker() {}
  35
  36 duration_type measure( duration_type overhead)
  37 {
  38     std::thread( worker).join();
  39
  40     duration_type result = duration_type::zero();
  41
  42     BOOST_PP_REPEAT_FROM_TO(1, JOBS, WAIT, _)
  43
  44     result /= JOBS;  // loops
  45
  46     return result;
  47 }
  48
  49 int main( int argc, char * argv[])
  50 {
  51     try
  52     {
  53         duration_type overhead = overhead_clock();
  54         boost::uint64_t res = measure( overhead).count();
  55         std::cout << "average of " << res << " nano seconds" << std::endl;
  56
  57         return EXIT_SUCCESS;
  58     }
  59     catch ( std::exception const& e)
  60     { std::cerr << "exception: " << e.what() << std::endl; }
  61     catch (...)
  62     { std::cerr << "unhandled exception" << std::endl; }
  63     return EXIT_FAILURE;
  64 }