folly/test/DeterministicSchedule.cpp

   1 /*
   2  * Copyright 2013 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 "DeterministicSchedule.h"
  18 #include <algorithm>
  19 #include <list>
  20 #include <mutex>
  21 #include <random>
  22 #include <utility>
  23 #include <unordered_map>
  24 #include <assert.h>
  25
  26 namespace folly { namespace test {
  27
  28 __thread sem_t* DeterministicSchedule::tls_sem;
  29 __thread DeterministicSchedule* DeterministicSchedule::tls_sched;
  30
  31 // access is protected by futexLock
  32 static std::unordered_map<detail::Futex<DeterministicAtomic>*,
  33                           std::list<std::pair<uint32_t,bool*>>> futexQueues;
  34
  35 static std::mutex futexLock;
  36
  37 DeterministicSchedule::DeterministicSchedule(
  38         const std::function<int(int)>& scheduler)
  39   : scheduler_(scheduler)
  40 {
  41   assert(tls_sem == nullptr);
  42   assert(tls_sched == nullptr);
  43
  44   tls_sem = new sem_t;
  45   sem_init(tls_sem, 0, 1);
  46   sems_.push_back(tls_sem);
  47
  48   tls_sched = this;
  49 }
  50
  51 DeterministicSchedule::~DeterministicSchedule() {
  52   assert(tls_sched == this);
  53   assert(sems_.size() == 1);
  54   assert(sems_[0] == tls_sem);
  55   beforeThreadExit();
  56 }
  57
  58 std::function<int(int)>
  59 DeterministicSchedule::uniform(long seed) {
  60   auto rand = std::make_shared<std::ranlux48>(seed);
  61   return [rand](int numActive) {
  62     auto dist = std::uniform_int_distribution<int>(0, numActive - 1);
  63     return dist(*rand);
  64   };
  65 }
  66
  67 struct UniformSubset {
  68   UniformSubset(long seed, int subsetSize, int stepsBetweenSelect)
  69     : uniform_(DeterministicSchedule::uniform(seed))
  70     , subsetSize_(subsetSize)
  71     , stepsBetweenSelect_(stepsBetweenSelect)
  72     , stepsLeft_(0)
  73   {
  74   }
  75
  76   int operator()(int numActive) {
  77     adjustPermSize(numActive);
  78     if (stepsLeft_-- == 0) {
  79       stepsLeft_ = stepsBetweenSelect_ - 1;
  80       shufflePrefix();
  81     }
  82     return perm_[uniform_(std::min(numActive, subsetSize_))];
  83   }
  84
  85  private:
  86   std::function<int(int)> uniform_;
  87   const int subsetSize_;
  88   const int stepsBetweenSelect_;
  89
  90   int stepsLeft_;
  91   // only the first subsetSize_ is properly randomized
  92   std::vector<int> perm_;
  93
  94   void adjustPermSize(int numActive) {
  95     if (perm_.size() > numActive) {
  96       perm_.erase(std::remove_if(perm_.begin(), perm_.end(),
  97               [=](int x){ return x >= numActive; }), perm_.end());
  98     } else {
  99       while (perm_.size() < numActive) {
 100         perm_.push_back(perm_.size());
 101       }
 102     }
 103     assert(perm_.size() == numActive);
 104   }
 105
 106   void shufflePrefix() {
 107     for (int i = 0; i < std::min(int(perm_.size() - 1), subsetSize_); ++i) {
 108       int j = uniform_(perm_.size() - i) + i;
 109       std::swap(perm_[i], perm_[j]);
 110     }
 111   }
 112 };
 113
 114 std::function<int(int)>
 115 DeterministicSchedule::uniformSubset(long seed, int n, int m) {
 116   auto gen = std::make_shared<UniformSubset>(seed, n, m);
 117   return [=](int numActive) { return (*gen)(numActive); };
 118 }
 119
 120 void
 121 DeterministicSchedule::beforeSharedAccess() {
 122   if (tls_sem) {
 123     sem_wait(tls_sem);
 124   }
 125 }
 126
 127 void
 128 DeterministicSchedule::afterSharedAccess() {
 129   auto sched = tls_sched;
 130   if (!sched) {
 131     return;
 132   }
 133
 134   sem_post(sched->sems_[sched->scheduler_(sched->sems_.size())]);
 135 }
 136
 137 sem_t*
 138 DeterministicSchedule::beforeThreadCreate() {
 139   sem_t* s = new sem_t;
 140   sem_init(s, 0, 0);
 141   beforeSharedAccess();
 142   sems_.push_back(s);
 143   afterSharedAccess();
 144   return s;
 145 }
 146
 147 void
 148 DeterministicSchedule::afterThreadCreate(sem_t* sem) {
 149   assert(tls_sem == nullptr);
 150   assert(tls_sched == nullptr);
 151   tls_sem = sem;
 152   tls_sched = this;
 153   bool started = false;
 154   while (!started) {
 155     beforeSharedAccess();
 156     if (active_.count(std::this_thread::get_id()) == 1) {
 157       started = true;
 158     }
 159     afterSharedAccess();
 160   }
 161 }
 162
 163 void
 164 DeterministicSchedule::beforeThreadExit() {
 165   assert(tls_sched == this);
 166   beforeSharedAccess();
 167   sems_.erase(std::find(sems_.begin(), sems_.end(), tls_sem));
 168   active_.erase(std::this_thread::get_id());
 169   if (sems_.size() > 0) {
 170     afterSharedAccess();
 171   }
 172   sem_destroy(tls_sem);
 173   delete tls_sem;
 174   tls_sem = nullptr;
 175   tls_sched = nullptr;
 176 }
 177
 178 void
 179 DeterministicSchedule::join(std::thread& child) {
 180   auto sched = tls_sched;
 181   if (sched) {
 182     bool done = false;
 183     while (!done) {
 184       beforeSharedAccess();
 185       done = !sched->active_.count(child.get_id());
 186       afterSharedAccess();
 187     }
 188   }
 189   child.join();
 190 }
 191
 192 void
 193 DeterministicSchedule::post(sem_t* sem) {
 194   beforeSharedAccess();
 195   sem_post(sem);
 196   afterSharedAccess();
 197 }
 198
 199 bool
 200 DeterministicSchedule::tryWait(sem_t* sem) {
 201   beforeSharedAccess();
 202   int rv = sem_trywait(sem);
 203   afterSharedAccess();
 204   if (rv == 0) {
 205     return true;
 206   } else {
 207     assert(errno == EAGAIN);
 208     return false;
 209   }
 210 }
 211
 212 void
 213 DeterministicSchedule::wait(sem_t* sem) {
 214   while (!tryWait(sem)) {
 215     // we're not busy waiting because this is a deterministic schedule
 216   }
 217 }
 218
 219 }}
 220
 221 namespace folly { namespace detail {
 222
 223 using namespace test;
 224
 225 template<>
 226 bool Futex<DeterministicAtomic>::futexWait(uint32_t expected,
 227                                            uint32_t waitMask) {
 228   bool rv;
 229   DeterministicSchedule::beforeSharedAccess();
 230   futexLock.lock();
 231   if (data != expected) {
 232     rv = false;
 233   } else {
 234     auto& queue = futexQueues[this];
 235     bool done = false;
 236     queue.push_back(std::make_pair(waitMask, &done));
 237     while (!done) {
 238       futexLock.unlock();
 239       DeterministicSchedule::afterSharedAccess();
 240       DeterministicSchedule::beforeSharedAccess();
 241       futexLock.lock();
 242     }
 243     rv = true;
 244   }
 245   futexLock.unlock();
 246   DeterministicSchedule::afterSharedAccess();
 247   return rv;
 248 }
 249
 250 template<>
 251 int Futex<DeterministicAtomic>::futexWake(int count, uint32_t wakeMask) {
 252   int rv = 0;
 253   DeterministicSchedule::beforeSharedAccess();
 254   futexLock.lock();
 255   if (futexQueues.count(this) > 0) {
 256     auto& queue = futexQueues[this];
 257     auto iter = queue.begin();
 258     while (iter != queue.end() && rv < count) {
 259       auto cur = iter++;
 260       if ((cur->first & wakeMask) != 0) {
 261         *(cur->second) = true;
 262         rv++;
 263         queue.erase(cur);
 264       }
 265     }
 266     if (queue.empty()) {
 267       futexQueues.erase(this);
 268     }
 269   }
 270   futexLock.unlock();
 271   DeterministicSchedule::afterSharedAccess();
 272   return rv;
 273 }
 274
 275
 276 template<>
 277 CacheLocality const& CacheLocality::system<test::DeterministicAtomic>() {
 278   static CacheLocality cache(CacheLocality::uniform(16));
 279   return cache;
 280 }
 281
 282 template<>
 283 test::DeterministicAtomic<size_t>
 284     SequentialThreadId<test::DeterministicAtomic>::prevId(0);
 285
 286 template<>
 287 __thread size_t SequentialThreadId<test::DeterministicAtomic>::currentId(0);
 288
 289 template<>
 290 const AccessSpreader<test::DeterministicAtomic>
 291 AccessSpreader<test::DeterministicAtomic>::stripeByCore(
 292     CacheLocality::system<>().numCachesByLevel.front());
 293
 294 template<>
 295 const AccessSpreader<test::DeterministicAtomic>
 296 AccessSpreader<test::DeterministicAtomic>::stripeByChip(
 297     CacheLocality::system<>().numCachesByLevel.back());
 298
 299 template<>
 300 AccessSpreaderArray<test::DeterministicAtomic,128>
 301 AccessSpreaderArray<test::DeterministicAtomic,128>::sharedInstance = {};
 302
 303
 304 template<>
 305 Getcpu::Func
 306 AccessSpreader<test::DeterministicAtomic>::pickGetcpuFunc(size_t numStripes) {
 307   return &SequentialThreadId<test::DeterministicAtomic>::getcpu;
 308 }
 309
 310 }}