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 <cstddef>
8 #include <cstdlib>
9 #include <iostream>
10 #include <stdexcept>
11 
12 #include <boost/context/detail/fcontext.hpp>
13 #include <boost/cstdint.hpp>
14 #include <boost/program_options.hpp>
15 
16 #include "../clock.hpp"
17 #include "../cycle.hpp"
18 
19 template< std::size_t Max, std::size_t Default, std::size_t Min >
20 class simple_stack_allocator
21 {
22 public:
maximum_stacksize()23     static std::size_t maximum_stacksize()
24     { return Max; }
25 
default_stacksize()26     static std::size_t default_stacksize()
27     { return Default; }
28 
minimum_stacksize()29     static std::size_t minimum_stacksize()
30     { return Min; }
31 
allocate(std::size_t size) const32     void * allocate( std::size_t size) const
33     {
34         BOOST_ASSERT( minimum_stacksize() <= size);
35         BOOST_ASSERT( maximum_stacksize() >= size);
36 
37         void * limit = std::malloc( size);
38         if ( ! limit) throw std::bad_alloc();
39 
40         return static_cast< char * >( limit) + size;
41     }
42 
deallocate(void * vp,std::size_t size) const43     void deallocate( void * vp, std::size_t size) const
44     {
45         BOOST_ASSERT( vp);
46         BOOST_ASSERT( minimum_stacksize() <= size);
47         BOOST_ASSERT( maximum_stacksize() >= size);
48 
49         void * limit = static_cast< char * >( vp) - size;
50         std::free( limit);
51     }
52 };
53 
54 typedef simple_stack_allocator<
55             8 * 1024 * 1024, 64 * 1024, 8 * 1024
56         >                                       stack_allocator;
57 
58 boost::uint64_t jobs = 1000000;
59 
foo(boost::context::detail::transfer_t t_)60 static void foo( boost::context::detail::transfer_t t_) {
61     boost::context::detail::transfer_t t = t_;
62     while ( true) {
63         t = boost::context::detail::jump_fcontext( t.fctx, 0);
64     }
65 }
66 
measure_time_fc()67 duration_type measure_time_fc() {
68     stack_allocator stack_alloc;
69     boost::context::detail::fcontext_t ctx = boost::context::detail::make_fcontext(
70             stack_alloc.allocate( stack_allocator::default_stacksize() ),
71             stack_allocator::default_stacksize(),
72             foo);
73 
74     // cache warum-up
75     boost::context::detail::transfer_t t = boost::context::detail::jump_fcontext( ctx, 0);
76 
77     time_point_type start( clock_type::now() );
78     for ( std::size_t i = 0; i < jobs; ++i) {
79         t = boost::context::detail::jump_fcontext( t.fctx, 0);
80     }
81     duration_type total = clock_type::now() - start;
82     total -= overhead_clock(); // overhead of measurement
83     total /= jobs;  // loops
84     total /= 2;  // 2x jump_fcontext
85 
86     return total;
87 }
88 
89 #ifdef BOOST_CONTEXT_CYCLE
measure_cycles_fc()90 cycle_type measure_cycles_fc() {
91     stack_allocator stack_alloc;
92     boost::context::detail::fcontext_t ctx = boost::context::detail::make_fcontext(
93             stack_alloc.allocate( stack_allocator::default_stacksize() ),
94             stack_allocator::default_stacksize(),
95             foo);
96 
97     // cache warum-up
98     boost::context::detail::transfer_t t = boost::context::detail::jump_fcontext( ctx, 0);
99 
100     cycle_type start( cycles() );
101     for ( std::size_t i = 0; i < jobs; ++i) {
102         t = boost::context::detail::jump_fcontext( t.fctx, 0);
103     }
104     cycle_type total = cycles() - start;
105     total -= overhead_cycle(); // overhead of measurement
106     total /= jobs;  // loops
107     total /= 2;  // 2x jump_fcontext
108 
109     return total;
110 }
111 #endif
112 
main(int argc,char * argv[])113 int main( int argc, char * argv[])
114 {
115     try
116     {
117         boost::program_options::options_description desc("allowed options");
118         desc.add_options()
119             ("help", "help message")
120             ("jobs,j", boost::program_options::value< boost::uint64_t >( & jobs), "jobs to run");
121 
122         boost::program_options::variables_map vm;
123         boost::program_options::store(
124                 boost::program_options::parse_command_line(
125                     argc,
126                     argv,
127                     desc),
128                 vm);
129         boost::program_options::notify( vm);
130 
131         if ( vm.count("help") ) {
132             std::cout << desc << std::endl;
133             return EXIT_SUCCESS;
134         }
135 
136         boost::uint64_t res = measure_time_fc().count();
137         std::cout << "fcontext_t: average of " << res << " nano seconds" << std::endl;
138 #ifdef BOOST_CONTEXT_CYCLE
139         res = measure_cycles_fc();
140         std::cout << "fcontext_t: average of " << res << " cpu cycles" << std::endl;
141 #endif
142 
143         return EXIT_SUCCESS;
144     }
145     catch ( std::exception const& e)
146     { std::cerr << "exception: " << e.what() << std::endl; }
147     catch (...)
148     { std::cerr << "unhandled exception" << std::endl; }
149     return EXIT_FAILURE;
150 }
151