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 "simix/context.h"
15 #include "gras_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;
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_FUTEX;
35 * This function is called by SIMIX_global_init() to initialize the context module.
37 void SIMIX_context_mod_init(void)
39 if (!simix_global->context_factory) {
40 /* select the context factory to use to create the contexts */
41 if (smx_factory_initializer_to_use) {
42 smx_factory_initializer_to_use(&simix_global->context_factory);
44 else { /* use the factory specified by --cfg=contexts/factory:value */
46 if (smx_context_factory_name == NULL) {
47 /* use the default factory */
49 SIMIX_ctx_raw_factory_init(&simix_global->context_factory);
50 #elif CONTEXT_UCONTEXT
51 SIMIX_ctx_sysv_factory_init(&simix_global->context_factory);
53 SIMIX_ctx_thread_factory_init(&simix_global->context_factory);
56 else if (!strcmp(smx_context_factory_name, "ucontext")) {
58 #ifdef CONTEXT_UCONTEXT
59 SIMIX_ctx_sysv_factory_init(&simix_global->context_factory);
61 xbt_die("The context factory 'ucontext' unavailable on your system");
64 else if (!strcmp(smx_context_factory_name, "thread")) {
65 /* use os threads (either pthreads or windows ones) */
66 SIMIX_ctx_thread_factory_init(&simix_global->context_factory);
68 else if (!strcmp(smx_context_factory_name, "raw")) {
69 /* use raw contexts */
70 SIMIX_ctx_raw_factory_init(&simix_global->context_factory);
73 XBT_ERROR("Invalid context factory specified. Valid factories on this machine:");
75 XBT_ERROR(" raw: high performance context factory implemented specifically for SimGrid");
77 XBT_ERROR(" (raw contextes are disabled at compilation time on this machine -- check configure logs for details)");
79 #ifdef CONTEXT_UCONTEXT
80 XBT_ERROR(" ucontext: classical system V contextes (implemented with makecontext, swapcontext and friends)");
82 XBT_ERROR(" (ucontext is disabled at compilation time on this machine -- check configure logs for details)");
84 XBT_ERROR(" thread: slow portability layer using system threads (pthreads on UNIX, CreateThread() on windows)");
85 xbt_die("Please use a valid factory.");
90 #if defined(CONTEXT_THREADS) && !defined(HAVE_THREAD_LOCAL_STORAGE)
91 /* the __thread storage class is not available on this platform:
92 * use getspecific/setspecific instead to store the current context in each thread */
93 xbt_os_thread_key_create(&smx_current_context_key);
98 * This function is call by SIMIX_clean() to finalize the context module.
100 void SIMIX_context_mod_exit(void)
102 if (simix_global->context_factory) {
103 smx_pfn_context_factory_finalize_t finalize_factory;
105 /* finalize the context factory */
106 finalize_factory = simix_global->context_factory->finalize;
107 finalize_factory(&simix_global->context_factory);
109 xbt_dict_remove((xbt_dict_t) _surf_cfg_set,"contexts/factory");
113 * \brief Returns whether some parallel threads are used
114 * for the user contexts.
115 * \return 1 if parallelism is used
117 XBT_INLINE int SIMIX_context_is_parallel(void) {
118 return smx_parallel_contexts > 1;
122 * \brief Returns the number of parallel threads used
123 * for the user contexts.
124 * \return the number of threads (1 means no parallelism)
126 XBT_INLINE int SIMIX_context_get_nthreads(void) {
127 return smx_parallel_contexts;
131 * \brief Sets the number of parallel threads to use
132 * for the user contexts.
134 * This function should be called before initializing SIMIX.
135 * A value of 1 means no parallelism (1 thread only).
136 * If the value is greater than 1, the thread support must be enabled.
138 * \param nb_threads the number of threads to use
140 XBT_INLINE void SIMIX_context_set_nthreads(int nb_threads) {
143 nb_threads = xbt_os_get_numcores();
144 XBT_INFO("Auto-setting contexts/nthreads to %d",nb_threads);
147 if (nb_threads > 1) {
148 #ifndef CONTEXT_THREADS
149 THROWF(arg_error, 0, "The thread factory cannot be run in parallel");
153 smx_parallel_contexts = nb_threads;
157 * \brief Returns the threshold above which user processes are run in parallel.
159 * If the number of threads is set to 1, there is no parallelism and this
160 * threshold has no effect.
162 * \return when the number of user processes ready to run is above
163 * this threshold, they are run in parallel
165 XBT_INLINE int SIMIX_context_get_parallel_threshold(void) {
166 return smx_parallel_threshold;
170 * \brief Sets the threshold above which user processes are run in parallel.
172 * If the number of threads is set to 1, there is no parallelism and this
173 * threshold has no effect.
175 * \param threshold when the number of user processes ready to run is above
176 * this threshold, they are run in parallel
178 XBT_INLINE void SIMIX_context_set_parallel_threshold(int threshold) {
179 smx_parallel_threshold = threshold;
183 * \brief Returns the synchronization mode used when processes are run in
185 * \return how threads are synchronized if processes are run in parallel
187 XBT_INLINE e_xbt_parmap_mode_t SIMIX_context_get_parallel_mode(void) {
188 return smx_parallel_synchronization_mode;
192 * \brief Sets the synchronization mode to use when processes are run in
194 * \param mode how to synchronize threads if processes are run in parallel
196 XBT_INLINE void SIMIX_context_set_parallel_mode(e_xbt_parmap_mode_t mode) {
197 smx_parallel_synchronization_mode = mode;
201 * \brief Returns the current context of this thread.
202 * \return the current context of this thread
204 XBT_INLINE smx_context_t SIMIX_context_get_current(void)
206 if (SIMIX_context_is_parallel()) {
207 #ifdef HAVE_THREAD_LOCAL_STORAGE
208 return smx_current_context_parallel;
210 return xbt_os_thread_get_specific(smx_current_context_key);
214 return smx_current_context_serial;
219 * \brief Sets the current context of this thread.
220 * \param context the context to set
222 XBT_INLINE void SIMIX_context_set_current(smx_context_t context)
224 if (SIMIX_context_is_parallel()) {
225 #ifdef HAVE_THREAD_LOCAL_STORAGE
226 smx_current_context_parallel = context;
228 xbt_os_thread_set_specific(smx_current_context_key, context);
232 smx_current_context_serial = context;