1 /* Copyright (c) 2007-2018. The SimGrid Team. All rights reserved. */
3 /* This program is free software; you can redistribute it and/or modify it
4 * under the terms of the license (GNU LGPL) which comes with this package. */
6 #include "SmpiHost.hpp"
9 #include "simgrid/s4u/Host.hpp"
10 #include "simgrid/s4u/Mailbox.hpp"
11 #include "smpi_coll.hpp"
12 #include "smpi_comm.hpp"
13 #include "smpi_group.hpp"
14 #include "smpi_info.hpp"
15 #include "smpi_process.hpp"
16 #include "src/msg/msg_private.hpp"
17 #include "src/simix/smx_private.hpp"
18 #include "src/surf/surf_interface.hpp"
19 #include "xbt/config.hpp"
21 #include <cfloat> /* DBL_MAX */
28 #include <sys/sendfile.h>
31 XBT_LOG_NEW_DEFAULT_SUBCATEGORY(smpi_kernel, smpi, "Logging specific to SMPI (kernel)");
32 #include <boost/tokenizer.hpp>
33 #include <boost/algorithm/string.hpp> /* trim_right / trim_left */
36 /* RTLD_DEEPBIND is a bad idea of GNU ld that obviously does not exist on other platforms
37 * See https://www.akkadia.org/drepper/dsohowto.pdf
38 * and https://lists.freebsd.org/pipermail/freebsd-current/2016-March/060284.html
40 #define RTLD_DEEPBIND 0
45 const char* papi_default_config_name = "default";
47 struct papi_process_data {
48 papi_counter_t counter_data;
53 using simgrid::s4u::Actor;
54 using simgrid::s4u::ActorPtr;
55 std::unordered_map<std::string, double> location2speedup;
57 static std::map</*process_id*/ int, simgrid::smpi::Process*> process_data;
58 int process_count = 0;
59 int smpi_universe_size = 0;
60 extern double smpi_total_benched_time;
61 xbt_os_timer_t global_timer;
63 * Setting MPI_COMM_WORLD to MPI_COMM_UNINITIALIZED (it's a variable)
64 * is important because the implementation of MPI_Comm checks
65 * "this == MPI_COMM_UNINITIALIZED"? If yes, it uses smpi_process()->comm_world()
67 * This is basically how we only have one global variable but all processes have
68 * different communicators (the one their SMPI instance uses).
70 * See smpi_comm.cpp and the functions therein for details.
72 MPI_Comm MPI_COMM_WORLD = MPI_COMM_UNINITIALIZED;
73 MPI_Errhandler *MPI_ERRORS_RETURN = nullptr;
74 MPI_Errhandler *MPI_ERRORS_ARE_FATAL = nullptr;
75 MPI_Errhandler *MPI_ERRHANDLER_NULL = nullptr;
76 // No instance gets manually created; check also the smpirun.in script as
77 // this default name is used there as well (when the <actor> tag is generated).
78 static const char* smpi_default_instance_name = "smpirun";
79 static simgrid::config::Flag<double> smpi_wtime_sleep(
80 "smpi/wtime", "Minimum time to inject inside a call to MPI_Wtime", 0.0);
81 static simgrid::config::Flag<double> smpi_init_sleep(
82 "smpi/init", "Time to inject inside a call to MPI_Init", 0.0);
84 void (*smpi_comm_copy_data_callback) (smx_activity_t, void*, size_t) = &smpi_comm_copy_buffer_callback;
86 void smpi_add_process(ActorPtr actor)
89 {actor->getPid()-1, new simgrid::smpi::Process(actor, nullptr)});
92 int smpi_process_count()
97 simgrid::smpi::Process* smpi_process()
99 ActorPtr me = Actor::self();
100 if (me == nullptr) // This happens sometimes (eg, when linking against NS3 because it pulls openMPI...)
102 simgrid::msg::ActorExt* msgExt = static_cast<simgrid::msg::ActorExt*>(me->getImpl()->userdata);
103 return static_cast<simgrid::smpi::Process*>(msgExt->data);
106 simgrid::smpi::Process* smpi_process_remote(int index)
108 return process_data.at(index);
111 MPI_Comm smpi_process_comm_self(){
112 return smpi_process()->comm_self();
115 void smpi_process_init(int *argc, char ***argv){
116 simgrid::smpi::Process::init(argc, argv);
119 int smpi_process_index(){
120 return smpi_process()->index();
123 void * smpi_process_get_user_data(){
124 return smpi_process()->get_user_data();
127 void smpi_process_set_user_data(void *data){
128 return smpi_process()->set_user_data(data);
132 int smpi_global_size()
134 char *value = getenv("SMPI_GLOBAL_SIZE");
135 xbt_assert(value,"Please set env var SMPI_GLOBAL_SIZE to the expected number of processes.");
137 return xbt_str_parse_int(value, "SMPI_GLOBAL_SIZE contains a non-numerical value: %s");
140 void smpi_comm_set_copy_data_callback(void (*callback) (smx_activity_t, void*, size_t))
142 smpi_comm_copy_data_callback = callback;
145 static void print(std::vector<std::pair<size_t, size_t>> vec) {
146 std::fprintf(stderr, "{");
147 for (auto const& elt : vec) {
148 std::fprintf(stderr, "(0x%zx, 0x%zx),", elt.first, elt.second);
150 std::fprintf(stderr, "}\n");
152 static void memcpy_private(void* dest, const void* src, std::vector<std::pair<size_t, size_t>>& private_blocks)
154 for (auto const& block : private_blocks)
155 memcpy((uint8_t*)dest+block.first, (uint8_t*)src+block.first, block.second-block.first);
158 static void check_blocks(std::vector<std::pair<size_t, size_t>> &private_blocks, size_t buff_size) {
159 for (auto const& block : private_blocks)
160 xbt_assert(block.first <= block.second && block.second <= buff_size, "Oops, bug in shared malloc.");
163 void smpi_comm_copy_buffer_callback(smx_activity_t synchro, void *buff, size_t buff_size)
165 simgrid::kernel::activity::CommImplPtr comm =
166 boost::dynamic_pointer_cast<simgrid::kernel::activity::CommImpl>(synchro);
169 size_t src_offset = 0;
170 size_t dst_offset = 0;
171 std::vector<std::pair<size_t, size_t>> src_private_blocks;
172 std::vector<std::pair<size_t, size_t>> dst_private_blocks;
173 XBT_DEBUG("Copy the data over");
174 if((src_shared=smpi_is_shared(buff, src_private_blocks, &src_offset))) {
175 XBT_DEBUG("Sender %p is shared. Let's ignore it.", buff);
176 src_private_blocks = shift_and_frame_private_blocks(src_private_blocks, src_offset, buff_size);
179 src_private_blocks.clear();
180 src_private_blocks.push_back(std::make_pair(0, buff_size));
182 if((dst_shared=smpi_is_shared((char*)comm->dst_buff, dst_private_blocks, &dst_offset))) {
183 XBT_DEBUG("Receiver %p is shared. Let's ignore it.", (char*)comm->dst_buff);
184 dst_private_blocks = shift_and_frame_private_blocks(dst_private_blocks, dst_offset, buff_size);
187 dst_private_blocks.clear();
188 dst_private_blocks.push_back(std::make_pair(0, buff_size));
190 check_blocks(src_private_blocks, buff_size);
191 check_blocks(dst_private_blocks, buff_size);
192 auto private_blocks = merge_private_blocks(src_private_blocks, dst_private_blocks);
193 check_blocks(private_blocks, buff_size);
195 if ((smpi_privatize_global_variables == SMPI_PRIVATIZE_MMAP) && (static_cast<char*>(buff) >= smpi_data_exe_start) &&
196 (static_cast<char*>(buff) < smpi_data_exe_start + smpi_data_exe_size)) {
197 XBT_DEBUG("Privatization : We are copying from a zone inside global memory... Saving data to temp buffer !");
199 smpi_switch_data_segment(
200 static_cast<simgrid::smpi::Process*>((static_cast<simgrid::msg::ActorExt*>(comm->src_proc->userdata)->data))
202 tmpbuff = static_cast<void*>(xbt_malloc(buff_size));
203 memcpy_private(tmpbuff, buff, private_blocks);
206 if ((smpi_privatize_global_variables == SMPI_PRIVATIZE_MMAP) && ((char*)comm->dst_buff >= smpi_data_exe_start) &&
207 ((char*)comm->dst_buff < smpi_data_exe_start + smpi_data_exe_size)) {
208 XBT_DEBUG("Privatization : We are copying to a zone inside global memory - Switch data segment");
209 smpi_switch_data_segment(
210 static_cast<simgrid::smpi::Process*>((static_cast<simgrid::msg::ActorExt*>(comm->dst_proc->userdata)->data))
213 XBT_DEBUG("Copying %zu bytes from %p to %p", buff_size, tmpbuff,comm->dst_buff);
214 memcpy_private(comm->dst_buff, tmpbuff, private_blocks);
216 if (comm->detached) {
217 // if this is a detached send, the source buffer was duplicated by SMPI
218 // sender to make the original buffer available to the application ASAP
220 //It seems that the request is used after the call there this should be free somewhere else but where???
221 //xbt_free(comm->comm.src_data);// inside SMPI the request is kept inside the user data and should be free
222 comm->src_buff = nullptr;
228 void smpi_comm_null_copy_buffer_callback(smx_activity_t comm, void *buff, size_t buff_size)
230 /* nothing done in this version */
233 static void smpi_check_options(){
234 //check correctness of MPI parameters
236 xbt_assert(xbt_cfg_get_int("smpi/async-small-thresh") <= xbt_cfg_get_int("smpi/send-is-detached-thresh"));
238 if (xbt_cfg_is_default_value("smpi/host-speed")) {
239 XBT_INFO("You did not set the power of the host running the simulation. "
240 "The timings will certainly not be accurate. "
241 "Use the option \"--cfg=smpi/host-speed:<flops>\" to set its value."
242 "Check http://simgrid.org/simgrid/latest/doc/options.html#options_smpi_bench for more information.");
245 xbt_assert(xbt_cfg_get_double("smpi/cpu-threshold") >=0,
246 "The 'smpi/cpu-threshold' option cannot have negative values [anymore]. If you want to discard "
247 "the simulation of any computation, please use 'smpi/simulate-computation:no' instead.");
251 return not process_data.empty();
254 void smpi_global_init()
256 if (not MC_is_active()) {
257 global_timer = xbt_os_timer_new();
258 xbt_os_walltimer_start(global_timer);
261 std::string filename = xbt_cfg_get_string("smpi/comp-adjustment-file");
262 if (not filename.empty()) {
263 std::ifstream fstream(filename);
264 if (not fstream.is_open()) {
265 xbt_die("Could not open file %s. Does it exist?", filename.c_str());
269 typedef boost::tokenizer< boost::escaped_list_separator<char>> Tokenizer;
270 std::getline(fstream, line); // Skip the header line
271 while (std::getline(fstream, line)) {
273 Tokenizer::iterator it = tok.begin();
274 Tokenizer::iterator end = std::next(tok.begin());
276 std::string location = *it;
277 boost::trim(location);
278 location2speedup.insert(std::pair<std::string, double>(location, std::stod(*end)));
283 // This map holds for each computation unit (such as "default" or "process1" etc.)
284 // the configuration as given by the user (counter data as a pair of (counter_name, counter_counter))
285 // and the (computed) event_set.
286 std::map</* computation unit name */ std::string, papi_process_data> units2papi_setup;
288 if (not xbt_cfg_get_string("smpi/papi-events").empty()) {
289 if (PAPI_library_init(PAPI_VER_CURRENT) != PAPI_VER_CURRENT)
290 XBT_ERROR("Could not initialize PAPI library; is it correctly installed and linked?"
291 " Expected version is %i",
294 typedef boost::tokenizer<boost::char_separator<char>> Tokenizer;
295 boost::char_separator<char> separator_units(";");
296 std::string str = xbt_cfg_get_string("smpi/papi-events");
297 Tokenizer tokens(str, separator_units);
299 // Iterate over all the computational units. This could be processes, hosts, threads, ranks... You name it.
300 // I'm not exactly sure what we will support eventually, so I'll leave it at the general term "units".
301 for (auto const& unit_it : tokens) {
302 boost::char_separator<char> separator_events(":");
303 Tokenizer event_tokens(unit_it, separator_events);
305 int event_set = PAPI_NULL;
306 if (PAPI_create_eventset(&event_set) != PAPI_OK) {
307 // TODO: Should this let the whole simulation die?
308 XBT_CRITICAL("Could not create PAPI event set during init.");
311 // NOTE: We cannot use a map here, as we must obey the order of the counters
312 // This is important for PAPI: We need to map the values of counters back
313 // to the event_names (so, when PAPI_read() has finished)!
314 papi_counter_t counters2values;
316 // Iterate over all counters that were specified for this specific
318 // Note that we need to remove the name of the unit
319 // (that could also be the "default" value), which always comes first.
320 // Hence, we start at ++(events.begin())!
321 for (Tokenizer::iterator events_it = ++(event_tokens.begin()); events_it != event_tokens.end(); ++events_it) {
323 int event_code = PAPI_NULL;
324 char* event_name = const_cast<char*>((*events_it).c_str());
325 if (PAPI_event_name_to_code(event_name, &event_code) == PAPI_OK) {
326 if (PAPI_add_event(event_set, event_code) != PAPI_OK) {
327 XBT_ERROR("Could not add PAPI event '%s'. Skipping.", event_name);
330 XBT_DEBUG("Successfully added PAPI event '%s' to the event set.", event_name);
333 XBT_CRITICAL("Could not find PAPI event '%s'. Skipping.", event_name);
337 counters2values.push_back(
338 // We cannot just pass *events_it, as this is of type const basic_string
339 std::make_pair<std::string, long long>(std::string(*events_it), 0));
342 std::string unit_name = *(event_tokens.begin());
343 papi_process_data config = {.counter_data = std::move(counters2values), .event_set = event_set};
345 units2papi_setup.insert(std::make_pair(unit_name, std::move(config)));
351 void smpi_global_destroy()
353 smpi_bench_destroy();
354 smpi_shared_destroy();
355 smpi_deployment_cleanup_instances();
356 for (auto& pair : process_data) {
357 auto& process = pair.second;
358 if (process->comm_self() != MPI_COMM_NULL) {
359 simgrid::smpi::Comm::destroy(process->comm_self());
361 if (process->comm_intra() != MPI_COMM_NULL) {
362 simgrid::smpi::Comm::destroy(process->comm_intra());
364 xbt_os_timer_free(process->timer());
365 xbt_mutex_destroy(process->mailboxes_mutex());
367 process_data.clear();
369 if (simgrid::smpi::Colls::smpi_coll_cleanup_callback != nullptr)
370 simgrid::smpi::Colls::smpi_coll_cleanup_callback();
372 MPI_COMM_WORLD = MPI_COMM_NULL;
374 if (not MC_is_active()) {
375 xbt_os_timer_free(global_timer);
378 if(smpi_privatize_global_variables == SMPI_PRIVATIZE_MMAP)
379 smpi_destroy_global_memory_segments();
383 static void smpi_init_options(){
384 // return if already called
385 if (smpi_cpu_threshold > -1)
387 simgrid::smpi::Colls::set_collectives();
388 simgrid::smpi::Colls::smpi_coll_cleanup_callback = nullptr;
389 smpi_cpu_threshold = xbt_cfg_get_double("smpi/cpu-threshold");
390 smpi_host_speed = xbt_cfg_get_double("smpi/host-speed");
391 std::string smpi_privatize_option = xbt_cfg_get_string("smpi/privatization");
392 if (smpi_privatize_option == "no" || smpi_privatize_option == "0")
393 smpi_privatize_global_variables = SMPI_PRIVATIZE_NONE;
394 else if (smpi_privatize_option == "yes" || smpi_privatize_option == "1")
395 smpi_privatize_global_variables = SMPI_PRIVATIZE_DEFAULT;
396 else if (smpi_privatize_option == "mmap")
397 smpi_privatize_global_variables = SMPI_PRIVATIZE_MMAP;
398 else if (smpi_privatize_option == "dlopen")
399 smpi_privatize_global_variables = SMPI_PRIVATIZE_DLOPEN;
401 xbt_die("Invalid value for smpi/privatization: '%s'", smpi_privatize_option.c_str());
403 #if defined(__FreeBSD__)
404 if (smpi_privatize_global_variables == SMPI_PRIVATIZE_MMAP) {
405 XBT_INFO("Mixing mmap privatization is broken on FreeBSD, switching to dlopen privatization instead.");
406 smpi_privatize_global_variables = SMPI_PRIVATIZE_DLOPEN;
410 if (smpi_cpu_threshold < 0)
411 smpi_cpu_threshold = DBL_MAX;
413 std::string val = xbt_cfg_get_string("smpi/shared-malloc");
414 if ((val == "yes") || (val == "1") || (val == "on") || (val == "global")) {
415 smpi_cfg_shared_malloc = shmalloc_global;
416 } else if (val == "local") {
417 smpi_cfg_shared_malloc = shmalloc_local;
418 } else if ((val == "no") || (val == "0") || (val == "off")) {
419 smpi_cfg_shared_malloc = shmalloc_none;
421 xbt_die("Invalid value '%s' for option smpi/shared-malloc. Possible values: 'on' or 'global', 'local', 'off'",
426 typedef std::function<int(int argc, char *argv[])> smpi_entry_point_type;
427 typedef int (* smpi_c_entry_point_type)(int argc, char **argv);
428 typedef void (*smpi_fortran_entry_point_type)();
430 static int smpi_run_entry_point(smpi_entry_point_type entry_point, std::vector<std::string> args)
432 char noarg[] = {'\0'};
433 const int argc = args.size();
434 std::unique_ptr<char*[]> argv(new char*[argc + 1]);
435 for (int i = 0; i != argc; ++i)
436 argv[i] = args[i].empty() ? noarg : &args[i].front();
437 argv[argc] = nullptr;
439 int res = entry_point(argc, argv.get());
441 XBT_WARN("SMPI process did not return 0. Return value : %d", res);
442 smpi_process()->set_return_value(res);
447 // TODO, remove the number of functions involved here
448 static smpi_entry_point_type smpi_resolve_function(void* handle)
450 smpi_fortran_entry_point_type entry_point_fortran = (smpi_fortran_entry_point_type)dlsym(handle, "user_main_");
451 if (entry_point_fortran != nullptr) {
452 return [entry_point_fortran](int argc, char** argv) {
453 smpi_process_init(&argc, &argv);
454 entry_point_fortran();
459 smpi_c_entry_point_type entry_point = (smpi_c_entry_point_type)dlsym(handle, "main");
460 if (entry_point != nullptr) {
464 return smpi_entry_point_type();
467 int smpi_main(const char* executable, int argc, char *argv[])
469 srand(SMPI_RAND_SEED);
471 if (getenv("SMPI_PRETEND_CC") != nullptr) {
472 /* Hack to ensure that smpicc can pretend to be a simple compiler. Particularly handy to pass it to the
473 * configuration tools */
479 SIMIX_global_init(&argc, argv);
480 MSG_init(&argc,argv);
482 SMPI_switch_data_segment = &smpi_switch_data_segment;
484 simgrid::s4u::Host::onCreation.connect([](simgrid::s4u::Host& host) {
485 host.extension_set(new simgrid::smpi::SmpiHost(&host));
488 // parse the platform file: get the host list
489 SIMIX_create_environment(argv[1]);
490 SIMIX_comm_set_copy_data_callback(smpi_comm_copy_buffer_callback);
494 if (smpi_privatize_global_variables == SMPI_PRIVATIZE_DLOPEN) {
496 std::string executable_copy = executable;
498 // Prepare the copy of the binary (get its size)
499 struct stat fdin_stat;
500 stat(executable_copy.c_str(), &fdin_stat);
501 off_t fdin_size = fdin_stat.st_size;
502 static std::size_t rank = 0;
504 simix_global->default_function = [executable_copy, fdin_size](std::vector<std::string> args) {
505 return std::function<void()>([executable_copy, fdin_size, args] {
507 // Copy the dynamic library:
508 std::string target_executable = executable_copy
509 + "_" + std::to_string(getpid())
510 + "_" + std::to_string(rank++) + ".so";
512 int fdin = open(executable_copy.c_str(), O_RDONLY);
513 xbt_assert(fdin >= 0, "Cannot read from %s", executable_copy.c_str());
514 int fdout = open(target_executable.c_str(), O_CREAT | O_RDWR, S_IRWXU);
515 xbt_assert(fdout >= 0, "Cannot write into %s", target_executable.c_str());
518 ssize_t sent_size = sendfile(fdout, fdin, NULL, fdin_size);
519 xbt_assert(sent_size == fdin_size,
520 "Error while copying %s: only %zd bytes copied instead of %ld (errno: %d -- %s)",
521 target_executable.c_str(), sent_size, fdin_size, errno, strerror(errno));
523 XBT_VERB("Copy %d bytes into %s", static_cast<int>(fdin_size), target_executable.c_str());
524 const int bufsize = 1024 * 1024 * 4;
526 while (int got = read(fdin, buf, bufsize)) {
528 xbt_assert(errno == EINTR, "Cannot read from %s", executable_copy.c_str());
532 while (int done = write(fdout, p, todo)) {
534 xbt_assert(errno == EINTR, "Cannot write into %s", target_executable.c_str());
546 // Load the copy and resolve the entry point:
547 void* handle = dlopen(target_executable.c_str(), RTLD_LAZY | RTLD_LOCAL | RTLD_DEEPBIND);
548 int saved_errno = errno;
549 if (xbt_cfg_get_boolean("smpi/keep-temps") == false)
550 unlink(target_executable.c_str());
551 if (handle == nullptr)
552 xbt_die("dlopen failed: %s (errno: %d -- %s)", dlerror(), saved_errno, strerror(saved_errno));
553 smpi_entry_point_type entry_point = smpi_resolve_function(handle);
555 xbt_die("Could not resolve entry point");
557 smpi_run_entry_point(entry_point, args);
564 // Load the dynamic library and resolve the entry point:
565 void* handle = dlopen(executable, RTLD_LAZY | RTLD_LOCAL | RTLD_DEEPBIND);
566 if (handle == nullptr)
567 xbt_die("dlopen failed for %s: %s (errno: %d -- %s)", executable, dlerror(), errno, strerror(errno));
568 smpi_entry_point_type entry_point = smpi_resolve_function(handle);
570 xbt_die("main not found in %s", executable);
571 // TODO, register the executable for SMPI privatization
573 // Execute the same entry point for each simulated process:
574 simix_global->default_function = [entry_point](std::vector<std::string> args) {
575 return std::function<void()>([entry_point, args] {
576 smpi_run_entry_point(entry_point, args);
583 SIMIX_launch_application(argv[2]);
584 SMPI_app_instance_register(smpi_default_instance_name, nullptr,
585 SIMIX_process_count()); // This call has a side effect on process_count...
586 MPI_COMM_WORLD = *smpi_deployment_comm_world(smpi_default_instance_name);
587 smpi_universe_size = process_count;
590 /* Clean IO before the run */
594 if (MC_is_active()) {
600 xbt_os_walltimer_stop(global_timer);
601 if (xbt_cfg_get_boolean("smpi/display-timing")){
602 double global_time = xbt_os_timer_elapsed(global_timer);
603 XBT_INFO("Simulated time: %g seconds. \n\n"
604 "The simulation took %g seconds (after parsing and platform setup)\n"
605 "%g seconds were actual computation of the application",
606 SIMIX_get_clock(), global_time , smpi_total_benched_time);
608 if (smpi_total_benched_time/global_time>=0.75)
609 XBT_INFO("More than 75%% of the time was spent inside the application code.\n"
610 "You may want to use sampling functions or trace replay to reduce this.");
614 for (int i = 0, count = smpi_process_count(); i < count; i++) {
615 if (process_data.at(i)->return_value() != 0) {
616 ret = process_data.at(i)->return_value(); // return first non 0 value
620 smpi_global_destroy();
627 // Called either directly from the user code, or from the code called by smpirun
629 simgrid::s4u::Actor::onCreation.connect([](simgrid::s4u::ActorPtr actor) {
630 smpi_add_process(actor);
634 smpi_check_options();
636 simgrid::surf::surfExitCallbacks.connect(TRACE_smpi_release);
637 if(smpi_privatize_global_variables == SMPI_PRIVATIZE_MMAP)
638 smpi_backup_global_memory_segment();
641 void SMPI_finalize(){
642 smpi_global_destroy();
645 void smpi_mpi_init() {
646 if(smpi_init_sleep > 0)
647 simcall_process_sleep(smpi_init_sleep);
650 double smpi_mpi_wtime(){
652 if (smpi_process()->initialized() != 0 && smpi_process()->finalized() == 0 && smpi_process()->sampling() == 0) {
654 time = SIMIX_get_clock();
655 // to avoid deadlocks if used as a break condition, such as
656 // while (MPI_Wtime(...) < time_limit) {
659 // because the time will not normally advance when only calls to MPI_Wtime
660 // are made -> deadlock (MPI_Wtime never reaches the time limit)
661 if(smpi_wtime_sleep > 0)
662 simcall_process_sleep(smpi_wtime_sleep);
665 time = SIMIX_get_clock();