2 * Copyright 2016 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.
22 #include <type_traits>
24 #include <unordered_set>
27 #include <folly/AtomicIntrusiveLinkedList.h>
28 #include <folly/Executor.h>
29 #include <folly/IntrusiveList.h>
30 #include <folly/Likely.h>
31 #include <folly/Try.h>
32 #include <folly/io/async/Request.h>
34 #include <folly/experimental/ExecutionObserver.h>
35 #include <folly/fibers/BoostContextCompatibility.h>
36 #include <folly/fibers/Fiber.h>
37 #include <folly/fibers/GuardPageAllocator.h>
38 #include <folly/fibers/TimeoutController.h>
39 #include <folly/fibers/traits.h>
51 class TimeoutController;
56 class InlineFunctionRunner {
58 virtual ~InlineFunctionRunner() {}
61 * func must be executed inline and only once.
63 virtual void run(folly::Function<void()> func) = 0;
68 * @brief Single-threaded task execution engine.
70 * FiberManager allows semi-parallel task execution on the same thread. Each
71 * task can notify FiberManager that it is blocked on something (via await())
72 * call. This will pause execution of this task and it will be resumed only
73 * when it is unblocked (via setData()).
75 class FiberManager : public ::folly::Executor {
78 static constexpr size_t kDefaultStackSize{16 * 1024};
81 * Maximum stack size for fibers which will be used for executing all the
84 size_t stackSize{kDefaultStackSize};
87 * Record exact amount of stack used.
89 * This is fairly expensive: we fill each newly allocated stack
90 * with some known value and find the boundary of unused stack
91 * with linear search every time we surrender the stack back to fibersPool.
92 * 0 disables stack recording.
94 size_t recordStackEvery{0};
97 * Keep at most this many free fibers in the pool.
98 * This way the total number of fibers in the system is always bounded
99 * by the number of active fibers + maxFibersPoolSize.
101 size_t maxFibersPoolSize{1000};
104 * Protect limited amount of fiber stacks with guard pages.
106 bool useGuardPages{true};
109 * Free unnecessary fibers in the fibers pool every fibersPoolResizePeriodMs
110 * milliseconds. If value is 0, periodic resizing of the fibers pool is
113 uint32_t fibersPoolResizePeriodMs{0};
115 constexpr Options() {}
118 using ExceptionCallback =
119 folly::Function<void(std::exception_ptr, std::string)>;
121 FiberManager(const FiberManager&) = delete;
122 FiberManager& operator=(const FiberManager&) = delete;
125 * Initializes, but doesn't start FiberManager loop
127 * @param loopController
128 * @param options FiberManager options
130 explicit FiberManager(
131 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>
145 std::unique_ptr<LoopController> loopController,
146 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) -> folly::Future<
194 typename folly::Unit::Lift<typename std::result_of<F()>::type>::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) -> folly::Future<
213 typename folly::Unit::Lift<typename std::result_of<F()>::type>::type>;
215 // Executor interface calls addTaskRemote
216 void add(folly::Func f) override {
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 runInMainContext(F&& func);
243 * Returns a refference to a fiber-local context for given Fiber. Should be
244 * always called with the same T for each fiber. Fiber-local context is lazily
245 * default-constructed on first request.
246 * When new task is scheduled via addTask / addTaskRemote from a fiber its
247 * fiber-local context is copied into the new fiber.
249 template <typename T>
252 template <typename T>
253 static T& localThread();
256 * @return How many fiber objects (and stacks) has this manager allocated.
258 size_t fibersAllocated() const;
261 * @return How many of the allocated fiber objects are currently
264 size_t fibersPoolSize() const;
267 * return true if running activeFiber_ is not nullptr.
269 bool hasActiveFiber() const;
272 * @return The currently running fiber or null if no fiber is executing.
274 Fiber* currentFiber() const {
275 return currentFiber_;
279 * @return What was the most observed fiber stack usage (in bytes).
281 size_t stackHighWatermark() const;
284 * Yield execution of the currently running fiber. Must only be called from a
285 * fiber executing on this FiberManager. The calling fiber will be scheduled
286 * when all other fibers have had a chance to run and the event loop is
292 * Setup fibers execution observation/instrumentation. Fiber locals are
293 * available to observer.
295 * @param observer Fiber's execution observer.
297 void setObserver(ExecutionObserver* observer);
300 * @return Current observer for this FiberManager. Returns nullptr
301 * if no observer has been set.
303 ExecutionObserver* getObserver();
306 * Setup fibers preempt runner.
308 void setPreemptRunner(InlineFunctionRunner* preemptRunner);
311 * Returns an estimate of the number of fibers which are waiting to run (does
312 * not include fibers or tasks scheduled remotely).
314 size_t runQueueSize() const {
315 return readyFibers_.size() + yieldedFibers_.size();
318 static FiberManager& getFiberManager();
319 static FiberManager* getFiberManagerUnsafe();
324 template <typename F>
325 struct AddTaskHelper;
326 template <typename F, typename G>
327 struct AddTaskFinallyHelper;
330 template <typename F>
331 explicit RemoteTask(F&& f)
332 : func(std::forward<F>(f)), rcontext(RequestContext::saveContext()) {}
333 template <typename F>
334 RemoteTask(F&& f, const Fiber::LocalData& localData_)
335 : func(std::forward<F>(f)),
336 localData(folly::make_unique<Fiber::LocalData>(localData_)),
337 rcontext(RequestContext::saveContext()) {}
338 folly::Function<void()> func;
339 std::unique_ptr<Fiber::LocalData> localData;
340 std::shared_ptr<RequestContext> rcontext;
341 AtomicIntrusiveLinkedListHook<RemoteTask> nextRemoteTask;
344 intptr_t activateFiber(Fiber* fiber);
345 intptr_t deactivateFiber(Fiber* fiber);
347 typedef folly::IntrusiveList<Fiber, &Fiber::listHook_> FiberTailQueue;
348 typedef folly::IntrusiveList<Fiber, &Fiber::globalListHook_>
349 GlobalFiberTailQueue;
351 Fiber* activeFiber_{nullptr}; /**< active fiber, nullptr on main context */
353 * Same as active fiber, but also set for functions run from fiber on main
356 Fiber* currentFiber_{nullptr};
358 FiberTailQueue readyFibers_; /**< queue of fibers ready to be executed */
359 FiberTailQueue yieldedFibers_; /**< queue of fibers which have yielded
361 FiberTailQueue fibersPool_; /**< pool of unitialized Fiber objects */
363 GlobalFiberTailQueue allFibers_; /**< list of all Fiber objects owned */
365 size_t fibersAllocated_{0}; /**< total number of fibers allocated */
366 size_t fibersPoolSize_{0}; /**< total number of fibers in the free pool */
367 size_t fibersActive_{0}; /**< number of running or blocked fibers */
368 size_t fiberId_{0}; /**< id of last fiber used */
371 * Maximum number of active fibers in the last period lasting
372 * Options::fibersPoolResizePeriod milliseconds.
374 size_t maxFibersActiveLastPeriod_{0};
376 FContext::ContextStruct mainContext_; /**< stores loop function context */
378 std::unique_ptr<LoopController> loopController_;
379 bool isLoopScheduled_{false}; /**< was the ready loop scheduled to run? */
382 * When we are inside FiberManager loop this points to FiberManager. Otherwise
385 static FOLLY_TLS FiberManager* currentFiberManager_;
388 * Allocator used to allocate stack for Fibers in the pool.
389 * Allocates stack on the stack of the main context.
391 GuardPageAllocator stackAllocator_;
393 const Options options_; /**< FiberManager options */
396 * Largest observed individual Fiber stack usage in bytes.
398 size_t stackHighWatermark_{0};
401 * Schedules a loop with loopController (unless already scheduled before).
403 void ensureLoopScheduled();
406 * @return An initialized Fiber object from the pool
411 * Sets local data for given fiber if all conditions are met.
413 void initLocalData(Fiber& fiber);
416 * Function passed to the await call.
418 folly::Function<void(Fiber&)> awaitFunc_;
421 * Function passed to the runInMainContext call.
423 folly::Function<void()> immediateFunc_;
428 InlineFunctionRunner* preemptRunner_{nullptr};
431 * Fiber's execution observer.
433 ExecutionObserver* observer_{nullptr};
435 ExceptionCallback exceptionCallback_; /**< task exception callback */
437 folly::AtomicIntrusiveLinkedList<Fiber, &Fiber::nextRemoteReady_>
440 folly::AtomicIntrusiveLinkedList<RemoteTask, &RemoteTask::nextRemoteTask>
443 std::shared_ptr<TimeoutController> timeoutManager_;
445 struct FibersPoolResizer {
446 explicit FibersPoolResizer(FiberManager& fm) : fiberManager_(fm) {}
450 FiberManager& fiberManager_;
453 FibersPoolResizer fibersPoolResizer_;
454 bool fibersPoolResizerScheduled_{false};
456 void doFibersPoolResizing();
459 * Only local of this type will be available for fibers.
461 std::type_index localType_;
463 void runReadyFiber(Fiber* fiber);
464 void remoteReadyInsert(Fiber* fiber);
466 #ifdef FOLLY_SANITIZE_ADDRESS
468 // These methods notify ASAN when a fiber is entered/exited so that ASAN can
469 // find the right stack extents when it needs to poison/unpoison the stack.
471 void registerStartSwitchStackWithAsan(
472 void** saveFakeStack,
473 const void* stackBase,
475 void registerFinishSwitchStackWithAsan(
477 const void** saveStackBase,
478 size_t* saveStackSize);
479 void unpoisonFiberStack(const Fiber* fiber);
481 #endif // FOLLY_SANITIZE_ADDRESS
484 bool alternateSignalStackRegistered_{false};
486 void registerAlternateSignalStack();
491 * @return true iff we are running in a fiber's context
493 inline bool onFiber() {
494 auto fm = FiberManager::getFiberManagerUnsafe();
495 return fm ? fm->hasActiveFiber() : false;
499 * Add a new task to be executed.
501 * @param func Task functor; must have a signature of `void func()`.
502 * The object will be destroyed once task execution is complete.
504 template <typename F>
505 inline void addTask(F&& func) {
506 return FiberManager::getFiberManager().addTask(std::forward<F>(func));
510 * Add a new task. When the task is complete, execute finally(Try<Result>&&)
511 * on the main context.
512 * Task functor is run and destroyed on the fiber context.
513 * Finally functor is run and destroyed on the main context.
515 * @param func Task functor; must have a signature of `T func()` for some T.
516 * @param finally Finally functor; must have a signature of
517 * `void finally(Try<T>&&)` and will be passed
518 * the result of func() (including the exception if occurred).
520 template <typename F, typename G>
521 inline void addTaskFinally(F&& func, G&& finally) {
522 return FiberManager::getFiberManager().addTaskFinally(
523 std::forward<F>(func), std::forward<G>(finally));
527 * Blocks task execution until given promise is fulfilled.
529 * Calls function passing in a Promise<T>, which has to be fulfilled.
531 * @return data which was used to fulfill the promise.
533 template <typename F>
534 typename FirstArgOf<F>::type::value_type inline await(F&& func);
537 * If called from a fiber, immediately switches to the FiberManager's context
538 * and runs func(), going back to the Fiber's context after completion.
539 * Outside a fiber, just calls func() directly.
541 * @return value returned by func().
543 template <typename F>
544 typename std::result_of<F()>::type inline runInMainContext(F&& func) {
545 auto fm = FiberManager::getFiberManagerUnsafe();
546 if (UNLIKELY(fm == nullptr)) {
549 return fm->runInMainContext(std::forward<F>(func));
553 * Returns a refference to a fiber-local context for given Fiber. Should be
554 * always called with the same T for each fiber. Fiber-local context is lazily
555 * default-constructed on first request.
556 * When new task is scheduled via addTask / addTaskRemote from a fiber its
557 * fiber-local context is copied into the new fiber.
559 template <typename T>
561 auto fm = FiberManager::getFiberManagerUnsafe();
563 return fm->local<T>();
565 return FiberManager::localThread<T>();
568 inline void yield() {
569 auto fm = FiberManager::getFiberManagerUnsafe();
573 std::this_thread::yield();
579 #include <folly/fibers/FiberManagerInternal-inl.h>