1 /* a fast and simple context switching library */
3 /* Copyright (c) 2009 - 2011. 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 "gras_config.h"
16 XBT_LOG_NEW_DEFAULT_SUBCATEGORY(simix_context, simix,
17 "Context switching mechanism");
19 char* smx_context_factory_name = NULL; /* factory name specified by --cfg=contexts/factory:value */
20 smx_ctx_factory_initializer_t smx_factory_initializer_to_use = NULL;
21 int smx_context_stack_size = 128 * 1024;
23 #ifdef HAVE_THREAD_LOCAL_STORAGE
24 static __thread smx_context_t smx_current_context_parallel;
26 static xbt_os_thread_key_t smx_current_context_key = 0;
28 static smx_context_t smx_current_context_serial;
29 static int smx_parallel_contexts = 1;
30 static int smx_parallel_threshold = 2;
31 static e_xbt_parmap_mode_t smx_parallel_synchronization_mode = XBT_PARMAP_DEFAULT;
34 * This function is called by SIMIX_global_init() to initialize the context module.
36 void SIMIX_context_mod_init(void)
38 if (!simix_global->context_factory) {
39 /* select the context factory to use to create the contexts */
40 if (smx_factory_initializer_to_use) {
41 smx_factory_initializer_to_use(&simix_global->context_factory);
43 else { /* use the factory specified by --cfg=contexts/factory:value */
45 if (smx_context_factory_name == NULL) {
46 /* use the default factory */
48 SIMIX_ctx_raw_factory_init(&simix_global->context_factory);
49 #elif CONTEXT_UCONTEXT
50 SIMIX_ctx_sysv_factory_init(&simix_global->context_factory);
52 SIMIX_ctx_thread_factory_init(&simix_global->context_factory);
55 else if (!strcmp(smx_context_factory_name, "ucontext")) {
57 #ifdef CONTEXT_UCONTEXT
58 SIMIX_ctx_sysv_factory_init(&simix_global->context_factory);
60 xbt_die("The context factory 'ucontext' unavailable on your system");
63 else if (!strcmp(smx_context_factory_name, "thread")) {
64 /* use os threads (either pthreads or windows ones) */
65 SIMIX_ctx_thread_factory_init(&simix_global->context_factory);
67 else if (!strcmp(smx_context_factory_name, "raw")) {
68 /* use raw contexts */
69 SIMIX_ctx_raw_factory_init(&simix_global->context_factory);
72 XBT_ERROR("Invalid context factory specified. Valid factories on this machine:");
74 XBT_ERROR(" raw: high performance context factory implemented specifically for SimGrid");
76 XBT_ERROR(" (raw contextes are disabled at compilation time on this machine -- check configure logs for details)");
78 #ifdef CONTEXT_UCONTEXT
79 XBT_ERROR(" ucontext: classical system V contextes (implemented with makecontext, swapcontext and friends)");
81 XBT_ERROR(" (ucontext is disabled at compilation time on this machine -- check configure logs for details)");
83 XBT_ERROR(" thread: slow portability layer using system threads (pthreads on UNIX, CreateThread() on windows)");
84 xbt_die("Please use a valid factory.");
89 #if defined(CONTEXT_THREADS) && !defined(HAVE_THREAD_LOCAL_STORAGE)
90 /* the __thread storage class is not available on this platform:
91 * use getspecific/setspecific instead to store the current context in each thread */
92 xbt_os_thread_key_create(&smx_current_context_key);
97 * This function is call by SIMIX_clean() to finalize the context module.
99 void SIMIX_context_mod_exit(void)
101 if (simix_global->context_factory) {
102 smx_pfn_context_factory_finalize_t finalize_factory;
104 /* finalize the context factory */
105 finalize_factory = simix_global->context_factory->finalize;
106 finalize_factory(&simix_global->context_factory);
108 xbt_dict_remove((xbt_dict_t) _surf_cfg_set,"contexts/factory");
112 * \brief Returns whether some parallel threads are used
113 * for the user contexts.
114 * \return 1 if parallelism is used
116 XBT_INLINE int SIMIX_context_is_parallel(void) {
117 return smx_parallel_contexts > 1;
121 * \brief Returns the number of parallel threads used
122 * for the user contexts.
123 * \return the number of threads (1 means no parallelism)
125 XBT_INLINE int SIMIX_context_get_nthreads(void) {
126 return smx_parallel_contexts;
130 * \brief Sets the number of parallel threads to use
131 * for the user contexts.
133 * This function should be called before initializing SIMIX.
134 * A value of 1 means no parallelism (1 thread only).
135 * If the value is greater than 1, the thread support must be enabled.
137 * \param nb_threads the number of threads to use
139 XBT_INLINE void SIMIX_context_set_nthreads(int nb_threads) {
142 nb_threads = xbt_os_get_numcores();
143 XBT_INFO("Auto-setting contexts/nthreads to %d",nb_threads);
146 if (nb_threads > 1) {
147 #ifndef CONTEXT_THREADS
148 THROWF(arg_error, 0, "The thread factory cannot be run in parallel");
152 smx_parallel_contexts = nb_threads;
156 * \brief Returns the threshold above which user processes are run in parallel.
158 * If the number of threads is set to 1, there is no parallelism and this
159 * threshold has no effect.
161 * \return when the number of user processes ready to run is above
162 * this threshold, they are run in parallel
164 XBT_INLINE int SIMIX_context_get_parallel_threshold(void) {
165 return smx_parallel_threshold;
169 * \brief Sets the threshold above which user processes are run in parallel.
171 * If the number of threads is set to 1, there is no parallelism and this
172 * threshold has no effect.
174 * \param threshold when the number of user processes ready to run is above
175 * this threshold, they are run in parallel
177 XBT_INLINE void SIMIX_context_set_parallel_threshold(int threshold) {
178 smx_parallel_threshold = threshold;
182 * \brief Returns the synchronization mode used when processes are run in
184 * \return how threads are synchronized if processes are run in parallel
186 XBT_INLINE e_xbt_parmap_mode_t SIMIX_context_get_parallel_mode(void) {
187 return smx_parallel_synchronization_mode;
191 * \brief Sets the synchronization mode to use when processes are run in
193 * \param mode how to synchronize threads if processes are run in parallel
195 XBT_INLINE void SIMIX_context_set_parallel_mode(e_xbt_parmap_mode_t mode) {
196 smx_parallel_synchronization_mode = mode;
200 * \brief Returns the current context of this thread.
201 * \return the current context of this thread
203 XBT_INLINE smx_context_t SIMIX_context_get_current(void)
205 if (SIMIX_context_is_parallel()) {
206 #ifdef HAVE_THREAD_LOCAL_STORAGE
207 return smx_current_context_parallel;
209 return xbt_os_thread_get_specific(smx_current_context_key);
213 return smx_current_context_serial;
218 * \brief Sets the current context of this thread.
219 * \param context the context to set
221 XBT_INLINE void SIMIX_context_set_current(smx_context_t context)
223 if (SIMIX_context_is_parallel()) {
224 #ifdef HAVE_THREAD_LOCAL_STORAGE
225 smx_current_context_parallel = context;
227 xbt_os_thread_set_specific(smx_current_context_key, context);
231 smx_current_context_serial = context;