1 /* A thread pool (C++ version). */
3 /* Copyright (c) 2004-2018 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. */
10 #define XBT_PARMAP_HPP
12 #include "src/internal_config.h" // HAVE_FUTEX_H
13 #include "src/kernel/context/Context.hpp"
15 #include <boost/optional.hpp>
16 #include <simgrid/simix.h>
19 #include <xbt/parmap.h>
20 #include <xbt/xbt_os_thread.h>
24 #include <linux/futex.h>
25 #include <sys/syscall.h>
28 XBT_LOG_EXTERNAL_CATEGORY(xbt_parmap);
33 /** \addtogroup XBT_parmap
35 * \brief Parallel map class
38 template <typename T> class Parmap {
40 Parmap(unsigned num_workers, e_xbt_parmap_mode_t mode);
41 Parmap(const Parmap&) = delete;
42 Parmap& operator=(const Parmap&) = delete;
44 void apply(void (*fun)(T), const std::vector<T>& data);
45 boost::optional<T> next();
48 enum Flag { PARMAP_WORK, PARMAP_DESTROY };
51 * \brief Thread data transmission structure
55 ThreadData(Parmap<T>& parmap, int id) : parmap(parmap), worker_id(id) {}
61 * \brief Synchronization object (different specializations).
65 explicit Synchro(Parmap<T>& parmap) : parmap(parmap) {}
66 virtual ~Synchro() = default;
68 * \brief Wakes all workers and waits for them to finish the tasks.
70 * This function is called by the controller thread.
72 virtual void master_signal() = 0;
74 * \brief Starts the parmap: waits for all workers to be ready and returns.
76 * This function is called by the controller thread.
78 virtual void master_wait() = 0;
80 * \brief Ends the parmap: wakes the controller thread when all workers terminate.
82 * This function is called by all worker threads when they end (not including the controller).
84 virtual void worker_signal() = 0;
86 * \brief Waits for some work to process.
88 * This function is called by each worker thread (not including the controller) when it has no more work to do.
90 * \param round the expected round number
92 virtual void worker_wait(unsigned) = 0;
97 class PosixSynchro : public Synchro {
99 explicit PosixSynchro(Parmap<T>& parmap);
101 void master_signal();
103 void worker_signal();
104 void worker_wait(unsigned round);
107 xbt_os_cond_t ready_cond;
108 xbt_os_mutex_t ready_mutex;
109 xbt_os_cond_t done_cond;
110 xbt_os_mutex_t done_mutex;
114 class FutexSynchro : public Synchro {
116 explicit FutexSynchro(Parmap<T>& parmap) : Synchro(parmap) {}
117 void master_signal();
119 void worker_signal();
120 void worker_wait(unsigned);
123 static void futex_wait(unsigned* uaddr, unsigned val);
124 static void futex_wake(unsigned* uaddr, unsigned val);
128 class BusyWaitSynchro : public Synchro {
130 explicit BusyWaitSynchro(Parmap<T>& parmap) : Synchro(parmap) {}
131 void master_signal();
133 void worker_signal();
134 void worker_wait(unsigned);
137 static void* worker_main(void* arg);
138 Synchro* new_synchro(e_xbt_parmap_mode_t mode);
141 Flag status; /**< is the parmap active or being destroyed? */
142 unsigned work_round; /**< index of the current round */
143 xbt_os_thread_t* workers; /**< worker thread handlers */
144 unsigned num_workers; /**< total number of worker threads including the controller */
145 Synchro* synchro; /**< synchronization object */
147 unsigned thread_counter = 0; /**< number of workers that have done the work */
148 void (*fun)(const T) = nullptr; /**< function to run in parallel on each element of data */
149 const std::vector<T>* data = nullptr; /**< parameters to pass to fun in parallel */
150 std::atomic<unsigned> index; /**< index of the next element of data to pick */
154 * \brief Creates a parallel map object
155 * \param num_workers number of worker threads to create
156 * \param mode how to synchronize the worker threads
158 template <typename T> Parmap<T>::Parmap(unsigned num_workers, e_xbt_parmap_mode_t mode)
160 XBT_CDEBUG(xbt_parmap, "Create new parmap (%u workers)", num_workers);
162 /* Initialize the thread pool data structure */
163 this->status = PARMAP_WORK;
164 this->work_round = 0;
165 this->workers = new xbt_os_thread_t[num_workers];
166 this->num_workers = num_workers;
167 this->synchro = new_synchro(mode);
169 /* Create the pool of worker threads */
170 this->workers[0] = nullptr;
171 #if HAVE_PTHREAD_SETAFFINITY
174 for (unsigned i = 1; i < num_workers; i++) {
175 ThreadData* data = new ThreadData(*this, i);
176 this->workers[i] = xbt_os_thread_create(nullptr, worker_main, data, nullptr);
177 #if HAVE_PTHREAD_SETAFFINITY
178 xbt_os_thread_bind(this->workers[i], core_bind);
179 if (core_bind != xbt_os_get_numcores() - 1)
188 * \brief Destroys a parmap
190 template <typename T> Parmap<T>::~Parmap()
192 status = PARMAP_DESTROY;
193 synchro->master_signal();
195 for (unsigned i = 1; i < num_workers; i++)
196 xbt_os_thread_join(workers[i], nullptr);
203 * \brief Applies a list of tasks in parallel.
204 * \param fun the function to call in parallel
205 * \param data each element of this vector will be passed as an argument to fun
207 template <typename T> void Parmap<T>::apply(void (*fun)(T), const std::vector<T>& data)
209 /* Assign resources to worker threads (we are maestro here)*/
213 this->synchro->master_signal(); // maestro runs futex_wake to wake all the minions (the working threads)
214 this->work(); // maestro works with its minions
215 this->synchro->master_wait(); // When there is no more work to do, then maestro waits for the last minion to stop
216 XBT_CDEBUG(xbt_parmap, "Job done"); // ... and proceeds
220 * \brief Returns a next task to process.
222 * Worker threads call this function to get more work.
224 * \return the next task to process, or throws a std::out_of_range exception if there is no more work
226 template <typename T> boost::optional<T> Parmap<T>::next()
228 unsigned index = this->index.fetch_add(1, std::memory_order_relaxed);
229 if (index < this->data->size())
230 return (*this->data)[index];
236 * \brief Main work loop: applies fun to elements in turn.
238 template <typename T> void Parmap<T>::work()
240 unsigned length = this->data->size();
241 unsigned index = this->index.fetch_add(1, std::memory_order_relaxed);
242 while (index < length) {
243 this->fun((*this->data)[index]);
244 index = this->index.fetch_add(1, std::memory_order_relaxed);
249 * Get a synchronization object for given mode.
250 * \param mode the synchronization mode
252 template <typename T> typename Parmap<T>::Synchro* Parmap<T>::new_synchro(e_xbt_parmap_mode_t mode)
254 if (mode == XBT_PARMAP_DEFAULT) {
256 mode = XBT_PARMAP_FUTEX;
258 mode = XBT_PARMAP_POSIX;
263 case XBT_PARMAP_POSIX:
264 res = new PosixSynchro(*this);
266 case XBT_PARMAP_FUTEX:
268 res = new FutexSynchro(*this);
270 xbt_die("Futex is not available on this OS.");
273 case XBT_PARMAP_BUSY_WAIT:
274 res = new BusyWaitSynchro(*this);
283 * \brief Main function of a worker thread.
285 template <typename T> void* Parmap<T>::worker_main(void* arg)
287 ThreadData* data = static_cast<ThreadData*>(arg);
288 Parmap<T>& parmap = data->parmap;
290 smx_context_t context = SIMIX_context_new(std::function<void()>(), nullptr, nullptr);
291 SIMIX_context_set_current(context);
293 XBT_CDEBUG(xbt_parmap, "New worker thread created");
295 /* Worker's main loop */
298 parmap.synchro->worker_wait(round);
299 if (parmap.status == PARMAP_DESTROY)
302 XBT_CDEBUG(xbt_parmap, "Worker %d got a job", data->worker_id);
304 parmap.synchro->worker_signal();
305 XBT_CDEBUG(xbt_parmap, "Worker %d has finished", data->worker_id);
307 /* We are destroying the parmap */
313 template <typename T> Parmap<T>::PosixSynchro::PosixSynchro(Parmap<T>& parmap) : Synchro(parmap)
315 ready_cond = xbt_os_cond_init();
316 ready_mutex = xbt_os_mutex_init();
317 done_cond = xbt_os_cond_init();
318 done_mutex = xbt_os_mutex_init();
321 template <typename T> Parmap<T>::PosixSynchro::~PosixSynchro()
323 xbt_os_cond_destroy(ready_cond);
324 xbt_os_mutex_destroy(ready_mutex);
325 xbt_os_cond_destroy(done_cond);
326 xbt_os_mutex_destroy(done_mutex);
329 template <typename T> void Parmap<T>::PosixSynchro::master_signal()
331 xbt_os_mutex_acquire(ready_mutex);
332 this->parmap.thread_counter = 1;
333 this->parmap.work_round++;
334 /* wake all workers */
335 xbt_os_cond_broadcast(ready_cond);
336 xbt_os_mutex_release(ready_mutex);
339 template <typename T> void Parmap<T>::PosixSynchro::master_wait()
341 xbt_os_mutex_acquire(done_mutex);
342 while (this->parmap.thread_counter < this->parmap.num_workers) {
343 /* wait for all workers to be ready */
344 xbt_os_cond_wait(done_cond, done_mutex);
346 xbt_os_mutex_release(done_mutex);
349 template <typename T> void Parmap<T>::PosixSynchro::worker_signal()
351 xbt_os_mutex_acquire(done_mutex);
352 this->parmap.thread_counter++;
353 if (this->parmap.thread_counter == this->parmap.num_workers) {
354 /* all workers have finished, wake the controller */
355 xbt_os_cond_signal(done_cond);
357 xbt_os_mutex_release(done_mutex);
360 template <typename T> void Parmap<T>::PosixSynchro::worker_wait(unsigned round)
362 xbt_os_mutex_acquire(ready_mutex);
363 /* wait for more work */
364 while (this->parmap.work_round != round) {
365 xbt_os_cond_wait(ready_cond, ready_mutex);
367 xbt_os_mutex_release(ready_mutex);
371 template <typename T> inline void Parmap<T>::FutexSynchro::futex_wait(unsigned* uaddr, unsigned val)
373 XBT_CVERB(xbt_parmap, "Waiting on futex %p", uaddr);
374 syscall(SYS_futex, uaddr, FUTEX_WAIT_PRIVATE, val, nullptr, nullptr, 0);
377 template <typename T> inline void Parmap<T>::FutexSynchro::futex_wake(unsigned* uaddr, unsigned val)
379 XBT_CVERB(xbt_parmap, "Waking futex %p", uaddr);
380 syscall(SYS_futex, uaddr, FUTEX_WAKE_PRIVATE, val, nullptr, nullptr, 0);
383 template <typename T> void Parmap<T>::FutexSynchro::master_signal()
385 __atomic_store_n(&this->parmap.thread_counter, 1, __ATOMIC_SEQ_CST);
386 __atomic_add_fetch(&this->parmap.work_round, 1, __ATOMIC_SEQ_CST);
387 /* wake all workers */
388 futex_wake(&this->parmap.work_round, std::numeric_limits<int>::max());
391 template <typename T> void Parmap<T>::FutexSynchro::master_wait()
393 unsigned count = __atomic_load_n(&this->parmap.thread_counter, __ATOMIC_SEQ_CST);
394 while (count < this->parmap.num_workers) {
395 /* wait for all workers to be ready */
396 futex_wait(&this->parmap.thread_counter, count);
397 count = __atomic_load_n(&this->parmap.thread_counter, __ATOMIC_SEQ_CST);
401 template <typename T> void Parmap<T>::FutexSynchro::worker_signal()
403 unsigned count = __atomic_add_fetch(&this->parmap.thread_counter, 1, __ATOMIC_SEQ_CST);
404 if (count == this->parmap.num_workers) {
405 /* all workers have finished, wake the controller */
406 futex_wake(&this->parmap.thread_counter, std::numeric_limits<int>::max());
410 template <typename T> void Parmap<T>::FutexSynchro::worker_wait(unsigned round)
412 unsigned work_round = __atomic_load_n(&this->parmap.work_round, __ATOMIC_SEQ_CST);
413 /* wait for more work */
414 while (work_round != round) {
415 futex_wait(&this->parmap.work_round, work_round);
416 work_round = __atomic_load_n(&this->parmap.work_round, __ATOMIC_SEQ_CST);
421 template <typename T> void Parmap<T>::BusyWaitSynchro::master_signal()
423 __atomic_store_n(&this->parmap.thread_counter, 1, __ATOMIC_SEQ_CST);
424 __atomic_add_fetch(&this->parmap.work_round, 1, __ATOMIC_SEQ_CST);
427 template <typename T> void Parmap<T>::BusyWaitSynchro::master_wait()
429 while (__atomic_load_n(&this->parmap.thread_counter, __ATOMIC_SEQ_CST) < this->parmap.num_workers) {
430 xbt_os_thread_yield();
434 template <typename T> void Parmap<T>::BusyWaitSynchro::worker_signal()
436 __atomic_add_fetch(&this->parmap.thread_counter, 1, __ATOMIC_SEQ_CST);
439 template <typename T> void Parmap<T>::BusyWaitSynchro::worker_wait(unsigned round)
441 /* wait for more work */
442 while (__atomic_load_n(&this->parmap.work_round, __ATOMIC_SEQ_CST) != round) {
443 xbt_os_thread_yield();