2 * Copyright 2015 Facebook, Inc.
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
8 * http://www.apache.org/licenses/LICENSE-2.0
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
23 #include <type_traits>
24 #include <unordered_set>
27 #include <folly/AtomicIntrusiveLinkedList.h>
28 #include <folly/Executor.h>
29 #include <folly/Likely.h>
30 #include <folly/IntrusiveList.h>
31 #include <folly/io/async/Request.h>
32 #include <folly/futures/Try.h>
34 #include <folly/experimental/ExecutionObserver.h>
35 #include <folly/experimental/fibers/BoostContextCompatibility.h>
36 #include <folly/experimental/fibers/Fiber.h>
37 #include <folly/experimental/fibers/GuardPageAllocator.h>
38 #include <folly/experimental/fibers/TimeoutController.h>
39 #include <folly/experimental/fibers/traits.h>
51 class TimeoutController;
57 class InlineFunctionRunner {
59 virtual ~InlineFunctionRunner() {}
62 * func must be executed inline and only once.
64 virtual void run(std::function<void()> func) = 0;
69 * @brief Single-threaded task execution engine.
71 * FiberManager allows semi-parallel task execution on the same thread. Each
72 * task can notify FiberManager that it is blocked on something (via await())
73 * call. This will pause execution of this task and it will be resumed only
74 * when it is unblocked (via setData()).
76 class FiberManager : public ::folly::Executor {
79 static constexpr size_t kDefaultStackSize{16 * 1024};
82 * Maximum stack size for fibers which will be used for executing all the
85 size_t stackSize{kDefaultStackSize};
88 * Record exact amount of stack used.
90 * This is fairly expensive: we fill each newly allocated stack
91 * with some known value and find the boundary of unused stack
92 * with linear search every time we surrender the stack back to fibersPool.
93 * 0 disables stack recording.
95 size_t recordStackEvery{0};
98 * Keep at most this many free fibers in the pool.
99 * This way the total number of fibers in the system is always bounded
100 * by the number of active fibers + maxFibersPoolSize.
102 size_t maxFibersPoolSize{1000};
105 * Protect limited amount of fiber stacks with guard pages.
107 bool useGuardPages{false};
110 * Free unnecessary fibers in the fibers pool every fibersPoolResizePeriodMs
111 * milliseconds. If value is 0, periodic resizing of the fibers pool is
114 uint32_t fibersPoolResizePeriodMs{0};
116 constexpr Options() {}
119 typedef std::function<void(std::exception_ptr, std::string)>
122 FiberManager(const FiberManager&) = delete;
123 FiberManager& operator=(const FiberManager&) = delete;
126 * Initializes, but doesn't start FiberManager loop
128 * @param loopController
129 * @param options FiberManager options
131 explicit FiberManager(std::unique_ptr<LoopController> loopController,
132 Options options = Options());
135 * Initializes, but doesn't start FiberManager loop
137 * @param loopController
138 * @param options FiberManager options
139 * @tparam LocalT only local of this type may be stored on fibers.
140 * Locals of other types will be considered thread-locals.
142 template <typename LocalT>
143 FiberManager(LocalType<LocalT>,
144 std::unique_ptr<LoopController> loopController,
145 Options options = Options());
153 LoopController& loopController();
154 const LoopController& loopController() const;
157 * Keeps running ready tasks until the list of ready tasks is empty.
159 * @return True if there are any waiting tasks remaining.
161 bool loopUntilNoReady();
164 * @return true if there are outstanding tasks.
166 bool hasTasks() const;
169 * Sets exception callback which will be called if any of the tasks throws an
174 void setExceptionCallback(ExceptionCallback ec);
177 * Add a new task to be executed. Must be called from FiberManager's thread.
179 * @param func Task functor; must have a signature of `void func()`.
180 * The object will be destroyed once task execution is complete.
182 template <typename F>
183 void addTask(F&& func);
186 * Add a new task to be executed and return a future that will be set on
187 * return from func. Must be called from FiberManager's thread.
189 * @param func Task functor; must have a signature of `void func()`.
190 * The object will be destroyed once task execution is complete.
192 template <typename F>
193 auto addTaskFuture(F&& func)
194 -> folly::Future<typename std::result_of<F()>::type>;
196 * Add a new task to be executed. Safe to call from other threads.
198 * @param func Task function; must have a signature of `void func()`.
199 * The object will be destroyed once task execution is complete.
201 template <typename F>
202 void addTaskRemote(F&& func);
205 * Add a new task to be executed and return a future that will be set on
206 * return from func. Safe to call from other threads.
208 * @param func Task function; must have a signature of `void func()`.
209 * The object will be destroyed once task execution is complete.
211 template <typename F>
212 auto addTaskRemoteFuture(F&& func)
213 -> folly::Future<typename std::result_of<F()>::type>;
215 // Executor interface calls addTaskRemote
216 void add(std::function<void()> f) {
217 addTaskRemote(std::move(f));
221 * Add a new task. When the task is complete, execute finally(Try<Result>&&)
222 * on the main context.
224 * @param func Task functor; must have a signature of `T func()` for some T.
225 * @param finally Finally functor; must have a signature of
226 * `void finally(Try<T>&&)` and will be passed
227 * the result of func() (including the exception if occurred).
229 template <typename F, typename G>
230 void addTaskFinally(F&& func, G&& finally);
233 * If called from a fiber, immediately switches to the FiberManager's context
234 * and runs func(), going back to the Fiber's context after completion.
235 * Outside a fiber, just calls func() directly.
237 * @return value returned by func().
239 template <typename F>
240 typename std::result_of<F()>::type
241 runInMainContext(F&& func);
244 * Returns a refference to a fiber-local context for given Fiber. Should be
245 * always called with the same T for each fiber. Fiber-local context is lazily
246 * default-constructed on first request.
247 * When new task is scheduled via addTask / addTaskRemote from a fiber its
248 * fiber-local context is copied into the new fiber.
250 template <typename T>
253 template <typename T>
254 static T& localThread();
257 * @return How many fiber objects (and stacks) has this manager allocated.
259 size_t fibersAllocated() const;
262 * @return How many of the allocated fiber objects are currently
265 size_t fibersPoolSize() const;
268 * return true if running activeFiber_ is not nullptr.
270 bool hasActiveFiber() const;
273 * @return The currently running fiber or null if no fiber is executing.
275 Fiber* currentFiber() const {
276 return currentFiber_;
280 * @return What was the most observed fiber stack usage (in bytes).
282 size_t stackHighWatermark() const;
285 * Yield execution of the currently running fiber. Must only be called from a
286 * fiber executing on this FiberManager. The calling fiber will be scheduled
287 * when all other fibers have had a chance to run and the event loop is
293 * Setup fibers execution observation/instrumentation. Fiber locals are
294 * available to observer.
296 * @param observer Fiber's execution observer.
298 void setObserver(ExecutionObserver* observer);
301 * Setup fibers preempt runner.
303 void setPreemptRunner(InlineFunctionRunner* preemptRunner);
306 * Returns an estimate of the number of fibers which are waiting to run (does
307 * not include fibers or tasks scheduled remotely).
309 size_t runQueueSize() const {
310 return readyFibers_.size() + yieldedFibers_.size();
313 static FiberManager& getFiberManager();
314 static FiberManager* getFiberManagerUnsafe();
319 template <typename F>
320 struct AddTaskHelper;
321 template <typename F, typename G>
322 struct AddTaskFinallyHelper;
325 template <typename F>
326 explicit RemoteTask(F&& f) :
327 func(std::forward<F>(f)),
328 rcontext(RequestContext::saveContext()) {}
329 template <typename F>
330 RemoteTask(F&& f, const Fiber::LocalData& localData_) :
331 func(std::forward<F>(f)),
332 localData(folly::make_unique<Fiber::LocalData>(localData_)),
333 rcontext(RequestContext::saveContext()) {}
334 std::function<void()> func;
335 std::unique_ptr<Fiber::LocalData> localData;
336 std::shared_ptr<RequestContext> rcontext;
337 AtomicIntrusiveLinkedListHook<RemoteTask> nextRemoteTask;
340 typedef folly::IntrusiveList<Fiber, &Fiber::listHook_> FiberTailQueue;
342 Fiber* activeFiber_{nullptr}; /**< active fiber, nullptr on main context */
344 * Same as active fiber, but also set for functions run from fiber on main
347 Fiber* currentFiber_{nullptr};
349 FiberTailQueue readyFibers_; /**< queue of fibers ready to be executed */
350 FiberTailQueue yieldedFibers_; /**< queue of fibers which have yielded
352 FiberTailQueue fibersPool_; /**< pool of unitialized Fiber objects */
354 size_t fibersAllocated_{0}; /**< total number of fibers allocated */
355 size_t fibersPoolSize_{0}; /**< total number of fibers in the free pool */
356 size_t fibersActive_{0}; /**< number of running or blocked fibers */
357 size_t fiberId_{0}; /**< id of last fiber used */
360 * Maximum number of active fibers in the last period lasting
361 * Options::fibersPoolResizePeriod milliseconds.
363 size_t maxFibersActiveLastPeriod_{0};
365 FContext::ContextStruct mainContext_; /**< stores loop function context */
367 std::unique_ptr<LoopController> loopController_;
368 bool isLoopScheduled_{false}; /**< was the ready loop scheduled to run? */
371 * When we are inside FiberManager loop this points to FiberManager. Otherwise
374 static FOLLY_TLS FiberManager* currentFiberManager_;
377 * runInMainContext implementation for non-void functions.
379 template <typename F>
380 typename std::enable_if<
381 !std::is_same<typename std::result_of<F()>::type, void>::value,
382 typename std::result_of<F()>::type>::type
383 runInMainContextHelper(F&& func);
386 * runInMainContext implementation for void functions
388 template <typename F>
389 typename std::enable_if<
390 std::is_same<typename std::result_of<F()>::type, void>::value,
392 runInMainContextHelper(F&& func);
395 * Allocator used to allocate stack for Fibers in the pool.
396 * Allocates stack on the stack of the main context.
398 GuardPageAllocator stackAllocator_;
400 const Options options_; /**< FiberManager options */
403 * Largest observed individual Fiber stack usage in bytes.
405 size_t stackHighWatermark_{0};
408 * Schedules a loop with loopController (unless already scheduled before).
410 void ensureLoopScheduled();
413 * @return An initialized Fiber object from the pool
418 * Sets local data for given fiber if all conditions are met.
420 void initLocalData(Fiber& fiber);
423 * Function passed to the await call.
425 std::function<void(Fiber&)> awaitFunc_;
428 * Function passed to the runInMainContext call.
430 std::function<void()> immediateFunc_;
435 InlineFunctionRunner* preemptRunner_{nullptr};
438 * Fiber's execution observer.
440 ExecutionObserver* observer_{nullptr};
442 ExceptionCallback exceptionCallback_; /**< task exception callback */
444 folly::AtomicIntrusiveLinkedList<Fiber, &Fiber::nextRemoteReady_>
447 folly::AtomicIntrusiveLinkedList<RemoteTask, &RemoteTask::nextRemoteTask>
450 std::shared_ptr<TimeoutController> timeoutManager_;
452 struct FibersPoolResizer {
453 explicit FibersPoolResizer(FiberManager& fm) :
457 FiberManager& fiberManager_;
460 FibersPoolResizer fibersPoolResizer_;
461 bool fibersPoolResizerScheduled_{false};
463 void doFibersPoolResizing();
466 * Only local of this type will be available for fibers.
468 std::type_index localType_;
470 void runReadyFiber(Fiber* fiber);
471 void remoteReadyInsert(Fiber* fiber);
475 * @return true iff we are running in a fiber's context
477 inline bool onFiber() {
478 auto fm = FiberManager::getFiberManagerUnsafe();
479 return fm ? fm->hasActiveFiber() : false;
483 * Add a new task to be executed.
485 * @param func Task functor; must have a signature of `void func()`.
486 * The object will be destroyed once task execution is complete.
488 template <typename F>
489 inline void addTask(F&& func) {
490 return FiberManager::getFiberManager().addTask(std::forward<F>(func));
494 * Add a new task. When the task is complete, execute finally(Try<Result>&&)
495 * on the main context.
496 * Task functor is run and destroyed on the fiber context.
497 * Finally functor is run and destroyed on the main context.
499 * @param func Task functor; must have a signature of `T func()` for some T.
500 * @param finally Finally functor; must have a signature of
501 * `void finally(Try<T>&&)` and will be passed
502 * the result of func() (including the exception if occurred).
504 template <typename F, typename G>
505 inline void addTaskFinally(F&& func, G&& finally) {
506 return FiberManager::getFiberManager().addTaskFinally(
507 std::forward<F>(func), std::forward<G>(finally));
511 * Blocks task execution until given promise is fulfilled.
513 * Calls function passing in a Promise<T>, which has to be fulfilled.
515 * @return data which was used to fulfill the promise.
517 template <typename F>
518 typename FirstArgOf<F>::type::value_type
519 inline await(F&& func);
522 * If called from a fiber, immediately switches to the FiberManager's context
523 * and runs func(), going back to the Fiber's context after completion.
524 * Outside a fiber, just calls func() directly.
526 * @return value returned by func().
528 template <typename F>
529 typename std::result_of<F()>::type
530 inline runInMainContext(F&& func) {
531 auto fm = FiberManager::getFiberManagerUnsafe();
532 if (UNLIKELY(fm == nullptr)) {
535 return fm->runInMainContext(std::forward<F>(func));
539 * Returns a refference to a fiber-local context for given Fiber. Should be
540 * always called with the same T for each fiber. Fiber-local context is lazily
541 * default-constructed on first request.
542 * When new task is scheduled via addTask / addTaskRemote from a fiber its
543 * fiber-local context is copied into the new fiber.
545 template <typename T>
547 auto fm = FiberManager::getFiberManagerUnsafe();
549 return fm->local<T>();
551 return FiberManager::localThread<T>();
554 inline void yield() {
555 auto fm = FiberManager::getFiberManagerUnsafe();
559 std::this_thread::yield();
565 #include "FiberManager-inl.h"