1 /* a fast and simple context switching library */
3 /* Copyright (c) 2009-2019. The SimGrid Team. All rights reserved. */
5 /* This program is free software; you can redistribute it and/or modify it
6 * under the terms of the license (GNU LGPL) which comes with this package. */
8 #include "src/simix/smx_private.hpp"
9 #include "xbt/config.hpp"
13 XBT_LOG_NEW_DEFAULT_SUBCATEGORY(simix_context, simix, "Context switching mechanism");
15 static std::pair<const char*, simgrid::kernel::context::ContextFactoryInitializer> context_factories[] = {
17 { "raw", &simgrid::kernel::context::raw_factory },
19 #if HAVE_UCONTEXT_CONTEXTS
20 { "ucontext", &simgrid::kernel::context::sysv_factory },
22 #if HAVE_BOOST_CONTEXTS
23 { "boost", &simgrid::kernel::context::boost_factory },
25 { "thread", &simgrid::kernel::context::thread_factory },
28 static_assert(sizeof(context_factories) != 0, "No context factories are enabled for this build");
30 // Create the list of possible contexts:
32 std::string contexts_list()
35 const std::size_t n = sizeof(context_factories) / sizeof(context_factories[0]);
36 for (std::size_t i = 1; i != n; ++i) {
38 res += context_factories[i].first;
43 static simgrid::config::Flag<std::string> context_factory_name(
45 (std::string("Possible values: ")+contexts_list()).c_str(),
46 context_factories[0].first);
48 unsigned smx_context_stack_size;
49 unsigned smx_context_guard_size;
50 static int smx_parallel_contexts = 1;
51 static int smx_parallel_threshold = 2;
52 static e_xbt_parmap_mode_t smx_parallel_synchronization_mode = XBT_PARMAP_DEFAULT;
55 * This function is called by SIMIX_global_init() to initialize the context module.
57 void SIMIX_context_mod_init()
59 xbt_assert(simix_global->context_factory == nullptr);
61 #if HAVE_SMPI && (defined(__APPLE__) || defined(__NetBSD__))
62 std::string priv = simgrid::config::get_value<std::string>("smpi/privatization");
63 if (context_factory_name == "thread" && (priv == "dlopen" || priv == "yes" || priv == "default" || priv == "1")) {
64 XBT_WARN("dlopen+thread broken on Apple and BSD. Switching to raw contexts.");
65 context_factory_name = "raw";
69 #if HAVE_SMPI && defined(__FreeBSD__)
70 if (context_factory_name == "thread" && simgrid::config::get_value<std::string>("smpi/privatization") != "no") {
71 XBT_WARN("mmap broken on FreeBSD, but dlopen+thread broken too. Switching to dlopen+raw contexts.");
72 context_factory_name = "raw";
76 /* select the context factory to use to create the contexts */
77 if (simgrid::kernel::context::factory_initializer != nullptr) { // Give Java a chance to hijack the factory mechanism
78 simix_global->context_factory = simgrid::kernel::context::factory_initializer();
81 /* use the factory specified by --cfg=contexts/factory:value */
82 for (auto const& factory : context_factories)
83 if (context_factory_name == factory.first) {
84 simix_global->context_factory = factory.second();
88 if (simix_global->context_factory == nullptr) {
89 XBT_ERROR("Invalid context factory specified. Valid factories on this machine:");
91 XBT_ERROR(" raw: high performance context factory implemented specifically for SimGrid");
93 XBT_ERROR(" (raw contexts were disabled at compilation time on this machine -- check configure logs for details)");
95 #if HAVE_UCONTEXT_CONTEXTS
96 XBT_ERROR(" ucontext: classical system V contexts (implemented with makecontext, swapcontext and friends)");
98 XBT_ERROR(" (ucontext was disabled at compilation time on this machine -- check configure logs for details)");
100 #if HAVE_BOOST_CONTEXTS
101 XBT_ERROR(" boost: this uses the boost libraries context implementation");
103 XBT_ERROR(" (boost was disabled at compilation time on this machine -- check configure logs for details. Did you install the libboost-context-dev package?)");
105 XBT_ERROR(" thread: slow portability layer using pthreads as provided by gcc");
106 xbt_die("Please use a valid factory.");
111 * This function is called by SIMIX_clean() to finalize the context module.
113 void SIMIX_context_mod_exit()
115 delete simix_global->context_factory;
116 simix_global->context_factory = nullptr;
119 /** @brief Returns whether some parallel threads are used for the user contexts. */
120 int SIMIX_context_is_parallel() {
121 return smx_parallel_contexts > 1;
125 * @brief Returns the number of parallel threads used for the user contexts.
126 * @return the number of threads (1 means no parallelism)
128 int SIMIX_context_get_nthreads() {
129 return smx_parallel_contexts;
133 * @brief Sets the number of parallel threads to use
134 * for the user contexts.
136 * This function should be called before initializing SIMIX.
137 * A value of 1 means no parallelism (1 thread only).
138 * If the value is greater than 1, the thread support must be enabled.
140 * @param nb_threads the number of threads to use
142 void SIMIX_context_set_nthreads(int nb_threads) {
144 nb_threads = std::thread::hardware_concurrency();
145 XBT_INFO("Auto-setting contexts/nthreads to %d", nb_threads);
147 smx_parallel_contexts = nb_threads;
151 * @brief Returns the threshold above which user processes are run in parallel.
153 * If the number of threads is set to 1, there is no parallelism and this
154 * threshold has no effect.
156 * @return when the number of user processes ready to run is above
157 * this threshold, they are run in parallel
159 int SIMIX_context_get_parallel_threshold() {
160 return smx_parallel_threshold;
164 * @brief Sets the threshold above which user processes are run in parallel.
166 * If the number of threads is set to 1, there is no parallelism and this
167 * threshold has no effect.
169 * @param threshold when the number of user processes ready to run is above
170 * this threshold, they are run in parallel
172 void SIMIX_context_set_parallel_threshold(int threshold) {
173 smx_parallel_threshold = threshold;
177 * @brief Returns the synchronization mode used when processes are run in
179 * @return how threads are synchronized if processes are run in parallel
181 e_xbt_parmap_mode_t SIMIX_context_get_parallel_mode() {
182 return smx_parallel_synchronization_mode;
186 * @brief Sets the synchronization mode to use when processes are run in
188 * @param mode how to synchronize threads if processes are run in parallel
190 void SIMIX_context_set_parallel_mode(e_xbt_parmap_mode_t mode) {
191 smx_parallel_synchronization_mode = mode;