1 /* a fast and simple context switching library */
3 /* Copyright (c) 2009-2020. 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/internal_config.h"
9 #include "src/simix/smx_private.hpp"
10 #include "smpi/smpi.h"
11 #include "xbt/config.hpp"
15 XBT_LOG_NEW_DEFAULT_SUBCATEGORY(simix_context, simix, "Context switching mechanism");
17 static std::pair<const char*, simgrid::kernel::context::ContextFactoryInitializer> context_factories[] = {
19 { "raw", &simgrid::kernel::context::raw_factory },
21 #if HAVE_UCONTEXT_CONTEXTS
22 { "ucontext", &simgrid::kernel::context::sysv_factory },
24 #if HAVE_BOOST_CONTEXTS
25 { "boost", &simgrid::kernel::context::boost_factory },
27 { "thread", &simgrid::kernel::context::thread_factory },
30 static_assert(sizeof(context_factories) != 0, "No context factories are enabled for this build");
32 // Create the list of possible contexts:
34 std::string contexts_list()
37 const std::size_t n = sizeof(context_factories) / sizeof(context_factories[0]);
38 for (std::size_t i = 1; i != n; ++i) {
40 res += context_factories[i].first;
45 static simgrid::config::Flag<std::string> context_factory_name(
47 (std::string("Possible values: ")+contexts_list()).c_str(),
48 context_factories[0].first);
50 unsigned smx_context_stack_size;
51 unsigned smx_context_guard_size;
52 static int smx_parallel_contexts = 1;
53 static int smx_parallel_threshold = 2;
54 static e_xbt_parmap_mode_t smx_parallel_synchronization_mode = XBT_PARMAP_DEFAULT;
57 * This function is called by SIMIX_global_init() to initialize the context module.
59 void SIMIX_context_mod_init()
61 xbt_assert(simix_global->context_factory == nullptr);
63 #if HAVE_SMPI && (defined(__APPLE__) || defined(__NetBSD__))
65 std::string priv = simgrid::config::get_value<std::string>("smpi/privatization");
66 if (context_factory_name == "thread" && (priv == "dlopen" || priv == "yes" || priv == "default" || priv == "1")) {
67 XBT_WARN("dlopen+thread broken on Apple and BSD. Switching to raw contexts.");
68 context_factory_name = "raw";
72 #if HAVE_SMPI && defined(__FreeBSD__)
74 if (context_factory_name == "thread" && simgrid::config::get_value<std::string>("smpi/privatization") != "no") {
75 XBT_WARN("mmap broken on FreeBSD, but dlopen+thread broken too. Switching to dlopen+raw contexts.");
76 context_factory_name = "raw";
80 /* select the context factory to use to create the contexts */
81 if (simgrid::kernel::context::factory_initializer != nullptr) { // Give Java a chance to hijack the factory mechanism
82 simix_global->context_factory = simgrid::kernel::context::factory_initializer();
85 /* use the factory specified by --cfg=contexts/factory:value */
86 for (auto const& factory : context_factories)
87 if (context_factory_name == factory.first) {
88 simix_global->context_factory = factory.second();
92 if (simix_global->context_factory == nullptr) {
93 XBT_ERROR("Invalid context factory specified. Valid factories on this machine:");
95 XBT_ERROR(" raw: high performance context factory implemented specifically for SimGrid");
97 XBT_ERROR(" (raw contexts were disabled at compilation time on this machine -- check configure logs for details)");
99 #if HAVE_UCONTEXT_CONTEXTS
100 XBT_ERROR(" ucontext: classical system V contexts (implemented with makecontext, swapcontext and friends)");
102 XBT_ERROR(" (ucontext was disabled at compilation time on this machine -- check configure logs for details)");
104 #if HAVE_BOOST_CONTEXTS
105 XBT_ERROR(" boost: this uses the boost libraries context implementation");
107 XBT_ERROR(" (boost was disabled at compilation time on this machine -- check configure logs for details. Did you install the libboost-context-dev package?)");
109 XBT_ERROR(" thread: slow portability layer using pthreads as provided by gcc");
110 xbt_die("Please use a valid factory.");
115 * This function is called by SIMIX_clean() to finalize the context module.
117 void SIMIX_context_mod_exit()
119 delete simix_global->context_factory;
120 simix_global->context_factory = nullptr;
123 /** @brief Returns whether some parallel threads are used for the user contexts. */
124 int SIMIX_context_is_parallel() {
125 return smx_parallel_contexts > 1;
129 * @brief Returns the number of parallel threads used for the user contexts.
130 * @return the number of threads (1 means no parallelism)
132 int SIMIX_context_get_nthreads() {
133 return smx_parallel_contexts;
137 * @brief Sets the number of parallel threads to use
138 * for the user contexts.
140 * This function should be called before initializing SIMIX.
141 * A value of 1 means no parallelism (1 thread only).
142 * If the value is greater than 1, the thread support must be enabled.
144 * @param nb_threads the number of threads to use
146 void SIMIX_context_set_nthreads(int nb_threads) {
148 nb_threads = std::thread::hardware_concurrency();
149 XBT_INFO("Auto-setting contexts/nthreads to %d", nb_threads);
151 smx_parallel_contexts = nb_threads;
155 * @brief Returns the threshold above which user processes are run in parallel.
157 * If the number of threads is set to 1, there is no parallelism and this
158 * threshold has no effect.
160 * @return when the number of user processes ready to run is above
161 * this threshold, they are run in parallel
163 int SIMIX_context_get_parallel_threshold() {
164 return smx_parallel_threshold;
168 * @brief Sets the threshold above which user processes are run in parallel.
170 * If the number of threads is set to 1, there is no parallelism and this
171 * threshold has no effect.
173 * @param threshold when the number of user processes ready to run is above
174 * this threshold, they are run in parallel
176 void SIMIX_context_set_parallel_threshold(int threshold) {
177 smx_parallel_threshold = threshold;
181 * @brief Returns the synchronization mode used when processes are run in
183 * @return how threads are synchronized if processes are run in parallel
185 e_xbt_parmap_mode_t SIMIX_context_get_parallel_mode() {
186 return smx_parallel_synchronization_mode;
190 * @brief Sets the synchronization mode to use when processes are run in
192 * @param mode how to synchronize threads if processes are run in parallel
194 void SIMIX_context_set_parallel_mode(e_xbt_parmap_mode_t mode) {
195 smx_parallel_synchronization_mode = mode;