1 /* a fast and simple context switching library */
3 /* Copyright (c) 2009-2013. The SimGrid Team.
4 * All rights reserved. */
6 /* This program is free software; you can redistribute it and/or modify it
7 * under the terms of the license (GNU LGPL) which comes with this package. */
12 #include "xbt/xbt_os_thread.h"
13 #include "smx_private.h"
14 #include "simgrid/sg_config.h"
15 #include "internal_config.h"
17 XBT_LOG_NEW_DEFAULT_SUBCATEGORY(simix_context, simix,
18 "Context switching mechanism");
20 char* smx_context_factory_name = NULL; /* factory name specified by --cfg=contexts/factory:value */
21 smx_ctx_factory_initializer_t smx_factory_initializer_to_use = NULL;
22 int smx_context_stack_size = 128 * 1024;
23 int smx_context_stack_size_was_set = 0;
24 #ifdef HAVE_THREAD_LOCAL_STORAGE
25 static __thread smx_context_t smx_current_context_parallel;
27 static xbt_os_thread_key_t smx_current_context_key = 0;
29 static smx_context_t smx_current_context_serial;
30 static int smx_parallel_contexts = 1;
31 static int smx_parallel_threshold = 2;
32 static e_xbt_parmap_mode_t smx_parallel_synchronization_mode = XBT_PARMAP_DEFAULT;
35 * This function is called by SIMIX_global_init() to initialize the context module.
37 void SIMIX_context_mod_init(void)
39 #if defined(CONTEXT_THREADS) && !defined(HAVE_THREAD_LOCAL_STORAGE)
40 /* the __thread storage class is not available on this platform:
41 * use getspecific/setspecific instead to store the current context in each thread */
42 xbt_os_thread_key_create(&smx_current_context_key);
44 if (!simix_global->context_factory) {
45 /* select the context factory to use to create the contexts */
46 if (smx_factory_initializer_to_use) {
47 smx_factory_initializer_to_use(&simix_global->context_factory);
49 else { /* use the factory specified by --cfg=contexts/factory:value */
52 if (!strcmp(smx_context_factory_name, "thread")) {
53 /* use os threads (either pthreads or windows ones) */
54 SIMIX_ctx_thread_factory_init(&simix_global->context_factory);
56 #ifdef CONTEXT_UCONTEXT
57 else if (!strcmp(smx_context_factory_name, "ucontext")) {
59 SIMIX_ctx_sysv_factory_init(&simix_global->context_factory);
63 else if (!strcmp(smx_context_factory_name, "raw")) {
64 /* use raw contexts */
65 SIMIX_ctx_raw_factory_init(&simix_global->context_factory);
69 XBT_ERROR("Invalid context factory specified. Valid factories on this machine:");
71 XBT_ERROR(" raw: high performance context factory implemented specifically for SimGrid");
73 XBT_ERROR(" (raw contexts are disabled at compilation time on this machine -- check configure logs for details)");
75 #ifdef CONTEXT_UCONTEXT
76 XBT_ERROR(" ucontext: classical system V contexts (implemented with makecontext, swapcontext and friends)");
78 XBT_ERROR(" (ucontext is disabled at compilation time on this machine -- check configure logs for details)");
80 XBT_ERROR(" thread: slow portability layer using system threads (pthreads on UNIX, CreateThread() on windows)");
81 xbt_die("Please use a valid factory.");
88 * This function is called by SIMIX_clean() to finalize the context module.
90 void SIMIX_context_mod_exit(void)
92 if (simix_global->context_factory) {
93 smx_pfn_context_factory_finalize_t finalize_factory;
95 /* finalize the context factory */
96 finalize_factory = simix_global->context_factory->finalize;
97 finalize_factory(&simix_global->context_factory);
99 xbt_dict_remove((xbt_dict_t) _sg_cfg_set,"contexts/factory");
103 * \brief Returns whether some parallel threads are used
104 * for the user contexts.
105 * \return 1 if parallelism is used
107 XBT_INLINE int SIMIX_context_is_parallel(void) {
108 return smx_parallel_contexts > 1;
112 * \brief Returns the number of parallel threads used
113 * for the user contexts.
114 * \return the number of threads (1 means no parallelism)
116 XBT_INLINE int SIMIX_context_get_nthreads(void) {
117 return smx_parallel_contexts;
121 * \brief Sets the number of parallel threads to use
122 * for the user contexts.
124 * This function should be called before initializing SIMIX.
125 * A value of 1 means no parallelism (1 thread only).
126 * If the value is greater than 1, the thread support must be enabled.
128 * \param nb_threads the number of threads to use
130 void SIMIX_context_set_nthreads(int nb_threads) {
132 nb_threads = xbt_os_get_numcores();
133 XBT_INFO("Auto-setting contexts/nthreads to %d",nb_threads);
136 if (nb_threads > 1) {
137 #ifndef CONTEXT_THREADS
138 THROWF(arg_error, 0, "The thread factory cannot be run in parallel");
141 smx_parallel_contexts = nb_threads;
145 * \brief Returns the threshold above which user processes are run in parallel.
147 * If the number of threads is set to 1, there is no parallelism and this
148 * threshold has no effect.
150 * \return when the number of user processes ready to run is above
151 * this threshold, they are run in parallel
153 XBT_INLINE int SIMIX_context_get_parallel_threshold(void) {
154 return smx_parallel_threshold;
158 * \brief Sets the threshold above which user processes are run in parallel.
160 * If the number of threads is set to 1, there is no parallelism and this
161 * threshold has no effect.
163 * \param threshold when the number of user processes ready to run is above
164 * this threshold, they are run in parallel
166 XBT_INLINE void SIMIX_context_set_parallel_threshold(int threshold) {
167 smx_parallel_threshold = threshold;
171 * \brief Returns the synchronization mode used when processes are run in
173 * \return how threads are synchronized if processes are run in parallel
175 XBT_INLINE e_xbt_parmap_mode_t SIMIX_context_get_parallel_mode(void) {
176 return smx_parallel_synchronization_mode;
180 * \brief Sets the synchronization mode to use when processes are run in
182 * \param mode how to synchronize threads if processes are run in parallel
184 XBT_INLINE void SIMIX_context_set_parallel_mode(e_xbt_parmap_mode_t mode) {
185 smx_parallel_synchronization_mode = mode;
189 * \brief Returns the current context of this thread.
190 * \return the current context of this thread
192 XBT_INLINE smx_context_t SIMIX_context_get_current(void)
194 if (SIMIX_context_is_parallel()) {
195 #ifdef HAVE_THREAD_LOCAL_STORAGE
196 return smx_current_context_parallel;
198 return xbt_os_thread_get_specific(smx_current_context_key);
202 return smx_current_context_serial;
207 * \brief Sets the current context of this thread.
208 * \param context the context to set
210 XBT_INLINE void SIMIX_context_set_current(smx_context_t context)
212 if (SIMIX_context_is_parallel()) {
213 #ifdef HAVE_THREAD_LOCAL_STORAGE
214 smx_current_context_parallel = context;
216 xbt_os_thread_set_specific(smx_current_context_key, context);
220 smx_current_context_serial = context;