folly/executors/GlobalExecutor.cpp

   1 /*
   2  * Copyright 2017 Facebook, Inc.
   3  *
   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
   7  *
   8  *   http://www.apache.org/licenses/LICENSE-2.0
   9  *
  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.
  15  */
  16
  17 #include <folly/Singleton.h>
  18 #include <folly/executors/IOExecutor.h>
  19 #include <folly/executors/IOThreadPoolExecutor.h>
  20 #include <folly/executors/InlineExecutor.h>
  21
  22 using namespace folly;
  23
  24 namespace {
  25
  26 // lock protecting global CPU executor
  27 struct CPUExecutorLock {};
  28 Singleton<RWSpinLock, CPUExecutorLock> globalCPUExecutorLock;
  29 // global CPU executor
  30 Singleton<std::weak_ptr<Executor>> globalCPUExecutor;
  31 // default global CPU executor is an InlineExecutor
  32 Singleton<std::shared_ptr<InlineExecutor>> globalInlineExecutor([] {
  33   return new std::shared_ptr<InlineExecutor>(
  34       std::make_shared<InlineExecutor>());
  35 });
  36
  37 // lock protecting global IO executor
  38 struct IOExecutorLock {};
  39 Singleton<RWSpinLock, IOExecutorLock> globalIOExecutorLock;
  40 // global IO executor
  41 Singleton<std::weak_ptr<IOExecutor>> globalIOExecutor;
  42 // default global IO executor is an IOThreadPoolExecutor
  43 Singleton<std::shared_ptr<IOThreadPoolExecutor>> globalIOThreadPool([] {
  44   return new std::shared_ptr<IOThreadPoolExecutor>(
  45       std::make_shared<IOThreadPoolExecutor>(
  46           sysconf(_SC_NPROCESSORS_ONLN),
  47           std::make_shared<NamedThreadFactory>("GlobalIOThreadPool")));
  48 });
  49 }
  50
  51 namespace folly {
  52
  53 template <class Exe, class DefaultExe, class LockTag>
  54 std::shared_ptr<Exe> getExecutor(
  55     Singleton<std::weak_ptr<Exe>>& sExecutor,
  56     Singleton<std::shared_ptr<DefaultExe>>& sDefaultExecutor,
  57     Singleton<RWSpinLock, LockTag>& sExecutorLock) {
  58   std::shared_ptr<Exe> executor;
  59   auto singleton = sExecutor.try_get();
  60   auto lock = sExecutorLock.try_get();
  61
  62   {
  63     RWSpinLock::ReadHolder guard(lock.get());
  64     if ((executor = sExecutor.try_get()->lock())) {
  65       return executor;
  66     }
  67   }
  68
  69   RWSpinLock::WriteHolder guard(lock.get());
  70   executor = singleton->lock();
  71   if (!executor) {
  72     std::weak_ptr<Exe> defaultExecutor = *sDefaultExecutor.try_get().get();
  73     executor = defaultExecutor.lock();
  74     sExecutor.try_get().get()->swap(defaultExecutor);
  75   }
  76   return executor;
  77 }
  78
  79 template <class Exe, class LockTag>
  80 void setExecutor(
  81     std::weak_ptr<Exe> executor,
  82     Singleton<std::weak_ptr<Exe>>& sExecutor,
  83     Singleton<RWSpinLock, LockTag>& sExecutorLock) {
  84   auto lock = sExecutorLock.try_get();
  85   RWSpinLock::WriteHolder guard(*lock);
  86   std::weak_ptr<Exe> executor_weak = std::move(executor);
  87   sExecutor.try_get().get()->swap(executor_weak);
  88 }
  89
  90 std::shared_ptr<Executor> getCPUExecutor() {
  91   return getExecutor(
  92       globalCPUExecutor, globalInlineExecutor, globalCPUExecutorLock);
  93 }
  94
  95 void setCPUExecutor(std::weak_ptr<Executor> executor) {
  96   setExecutor(std::move(executor), globalCPUExecutor, globalCPUExecutorLock);
  97 }
  98
  99 std::shared_ptr<IOExecutor> getIOExecutor() {
 100   return getExecutor(
 101       globalIOExecutor, globalIOThreadPool, globalIOExecutorLock);
 102 }
 103
 104 EventBase* getEventBase() {
 105   return getIOExecutor()->getEventBase();
 106 }
 107
 108 void setIOExecutor(std::weak_ptr<IOExecutor> executor) {
 109   setExecutor(std::move(executor), globalIOExecutor, globalIOExecutorLock);
 110 }
 111
 112 } // namespace folly