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.
21 #include <unordered_set>
24 #include <folly/AtomicLinkedList.h>
25 #include <folly/Likely.h>
26 #include <folly/IntrusiveList.h>
27 #include <folly/futures/Try.h>
29 #include <folly/experimental/fibers/BoostContextCompatibility.h>
30 #include <folly/experimental/fibers/Fiber.h>
31 #include <folly/experimental/fibers/traits.h>
33 #ifdef USE_GUARD_ALLOCATOR
34 #include <folly/experimental/fibers/GuardPageAllocator.h>
37 namespace folly { namespace fibers {
42 class TimeoutController;
46 * @brief Single-threaded task execution engine.
48 * FiberManager allows semi-parallel task execution on the same thread. Each
49 * task can notify FiberManager that it is blocked on something (via await())
50 * call. This will pause execution of this task and it will be resumed only
51 * when it is unblocked (via setData()).
56 #ifdef FOLLY_SANITIZE_ADDRESS
57 /* ASAN needs a lot of extra stack space.
58 16x is a conservative estimate, 8x also worked with tests
59 where it mattered. Note that overallocating here does not necessarily
60 increase RSS, since unused memory is pretty much free. */
61 static constexpr size_t kDefaultStackSize{16 * 16 * 1024};
63 static constexpr size_t kDefaultStackSize{16 * 1024};
66 * Maximum stack size for fibers which will be used for executing all the
69 size_t stackSize{kDefaultStackSize};
72 * Record exact amount of stack used.
74 * This is fairly expensive: we fill each newly allocated stack
75 * with some known value and find the boundary of unused stack
76 * with linear search every time we surrender the stack back to fibersPool.
78 bool debugRecordStackUsed{false};
81 * Keep at most this many free fibers in the pool.
82 * This way the total number of fibers in the system is always bounded
83 * by the number of active fibers + maxFibersPoolSize.
85 size_t maxFibersPoolSize{1000};
87 constexpr Options() {}
90 typedef std::function<void(std::exception_ptr, std::string)>
94 * Initializes, but doesn't start FiberManager loop
96 * @param options FiberManager options
98 explicit FiberManager(std::unique_ptr<LoopController> loopController,
99 Options options = Options());
106 LoopController& loopController();
107 const LoopController& loopController() const;
110 * Keeps running ready tasks until the list of ready tasks is empty.
112 * @return True if there are any waiting tasks remaining.
114 bool loopUntilNoReady();
117 * @return true if there are outstanding tasks.
119 bool hasTasks() const;
122 * Sets exception callback which will be called if any of the tasks throws an
127 void setExceptionCallback(ExceptionCallback ec);
130 * Add a new task to be executed. Must be called from FiberManager's thread.
132 * @param func Task functor; must have a signature of `void func()`.
133 * The object will be destroyed once task execution is complete.
135 template <typename F>
136 void addTask(F&& func);
139 * Add a new task to be executed, along with a function readyFunc_ which needs
140 * to be executed just before jumping to the ready fiber
142 * @param func Task functor; must have a signature of `T func()` for some T.
143 * @param readyFunc functor that needs to be executed just before jumping to
144 * ready fiber on the main context. This can for example be
145 * used to set up state before starting or resuming a fiber.
147 template <typename F, typename G>
148 void addTaskReadyFunc(F&& func, G&& readyFunc);
151 * Add a new task to be executed. Safe to call from other threads.
153 * @param func Task function; must have a signature of `void func()`.
154 * The object will be destroyed once task execution is complete.
156 template <typename F>
157 void addTaskRemote(F&& func);
160 * Add a new task. When the task is complete, execute finally(Try<Result>&&)
161 * on the main context.
163 * @param func Task functor; must have a signature of `T func()` for some T.
164 * @param finally Finally functor; must have a signature of
165 * `void finally(Try<T>&&)` and will be passed
166 * the result of func() (including the exception if occurred).
168 template <typename F, typename G>
169 void addTaskFinally(F&& func, G&& finally);
172 * If called from a fiber, immediately switches to the FiberManager's context
173 * and runs func(), going back to the Fiber's context after completion.
174 * Outside a fiber, just calls func() directly.
176 * @return value returned by func().
178 template <typename F>
179 typename std::result_of<F()>::type
180 runInMainContext(F&& func);
183 * @return How many fiber objects (and stacks) has this manager allocated.
185 size_t fibersAllocated() const;
188 * @return How many of the allocated fiber objects are currently
191 size_t fibersPoolSize() const;
194 * return true if running activeFiber_ is not nullptr.
196 bool hasActiveFiber();
199 * @return What was the most observed fiber stack usage (in bytes).
201 size_t stackHighWatermark() const;
203 static FiberManager& getFiberManager();
204 static FiberManager* getFiberManagerUnsafe();
209 template <typename F>
210 struct AddTaskHelper;
211 template <typename F, typename G>
212 struct AddTaskFinallyHelper;
215 template <typename F>
216 explicit RemoteTask(F&& f) : func(std::move(f)) {}
217 std::function<void()> func;
218 folly::AtomicLinkedListHook<RemoteTask> nextRemoteTask;
221 typedef folly::IntrusiveList<Fiber, &Fiber::listHook_> FiberTailQueue;
223 Fiber* activeFiber_{nullptr}; /**< active fiber, nullptr on main context */
225 FiberTailQueue readyFibers_; /**< queue of fibers ready to be executed */
226 FiberTailQueue fibersPool_; /**< pool of unitialized Fiber objects */
228 size_t fibersAllocated_{0}; /**< total number of fibers allocated */
229 size_t fibersPoolSize_{0}; /**< total number of fibers in the free pool */
230 size_t fibersActive_{0}; /**< number of running or blocked fibers */
232 FContext::ContextStruct mainContext_; /**< stores loop function context */
234 std::unique_ptr<LoopController> loopController_;
235 bool isLoopScheduled_{false}; /**< was the ready loop scheduled to run? */
238 * When we are inside FiberManager loop this points to FiberManager. Otherwise
241 static __thread FiberManager* currentFiberManager_;
244 * runInMainContext implementation for non-void functions.
246 template <typename F>
247 typename std::enable_if<
248 !std::is_same<typename std::result_of<F()>::type, void>::value,
249 typename std::result_of<F()>::type>::type
250 runInMainContextHelper(F&& func);
253 * runInMainContext implementation for void functions
255 template <typename F>
256 typename std::enable_if<
257 std::is_same<typename std::result_of<F()>::type, void>::value,
259 runInMainContextHelper(F&& func);
262 * Allocator used to allocate stack for Fibers in the pool.
263 * Allocates stack on the stack of the main context.
265 #ifdef USE_GUARD_ALLOCATOR
266 /* This is too slow for production use; can be fixed
267 if we allocated all stack storage once upfront */
268 GuardPageAllocator stackAllocator_;
270 std::allocator<unsigned char> stackAllocator_;
273 const Options options_; /**< FiberManager options */
276 * Largest observed individual Fiber stack usage in bytes.
278 size_t stackHighWatermark_{0};
281 * Schedules a loop with loopController (unless already scheduled before).
283 void ensureLoopScheduled();
286 * @return An initialized Fiber object from the pool
291 * Function passed to the await call.
293 std::function<void(Fiber&)> awaitFunc_;
296 * Function passed to the runInMainContext call.
298 std::function<void()> immediateFunc_;
300 ExceptionCallback exceptionCallback_; /**< task exception callback */
302 folly::AtomicLinkedList<Fiber, &Fiber::nextRemoteReady_> remoteReadyQueue_;
304 folly::AtomicLinkedList<RemoteTask, &RemoteTask::nextRemoteTask>
307 std::shared_ptr<TimeoutController> timeoutManager_;
309 void runReadyFiber(Fiber* fiber);
310 void remoteReadyInsert(Fiber* fiber);
314 * @return true iff we are running in a fiber's context
316 inline bool onFiber() {
317 auto fm = FiberManager::getFiberManagerUnsafe();
318 return fm ? fm->hasActiveFiber() : false;
322 * Add a new task to be executed.
324 * @param func Task functor; must have a signature of `void func()`.
325 * The object will be destroyed once task execution is complete.
327 template <typename F>
328 inline void addTask(F&& func) {
329 return FiberManager::getFiberManager().addTask(std::forward<F>(func));
333 * Add a new task. When the task is complete, execute finally(Try<Result>&&)
334 * on the main context.
335 * Task functor is run and destroyed on the fiber context.
336 * Finally functor is run and destroyed on the main context.
338 * @param func Task functor; must have a signature of `T func()` for some T.
339 * @param finally Finally functor; must have a signature of
340 * `void finally(Try<T>&&)` and will be passed
341 * the result of func() (including the exception if occurred).
343 template <typename F, typename G>
344 inline void addTaskFinally(F&& func, G&& finally) {
345 return FiberManager::getFiberManager().addTaskFinally(
346 std::forward<F>(func), std::forward<G>(finally));
350 * Blocks task execution until given promise is fulfilled.
352 * Calls function passing in a Promise<T>, which has to be fulfilled.
354 * @return data which was used to fulfill the promise.
356 template <typename F>
357 typename FirstArgOf<F>::type::value_type
358 inline await(F&& func);
361 * If called from a fiber, immediately switches to the FiberManager's context
362 * and runs func(), going back to the Fiber's context after completion.
363 * Outside a fiber, just calls func() directly.
365 * @return value returned by func().
367 template <typename F>
368 typename std::result_of<F()>::type
369 inline runInMainContext(F&& func) {
370 auto fm = FiberManager::getFiberManagerUnsafe();
371 if (UNLIKELY(fm == nullptr)) {
374 return fm->runInMainContext(std::forward<F>(func));
379 #include "FiberManager-inl.h"