Gavin Andresen
12 years ago
9 changed files with 342 additions and 41 deletions
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// Copyright (c) 2012 The Bitcoin developers
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// Distributed under the MIT/X11 software license, see the accompanying
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// file COPYING or http://www.opensource.org/licenses/mit-license.php.
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#ifndef CHECKQUEUE_H |
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#define CHECKQUEUE_H |
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#include <boost/thread/mutex.hpp> |
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#include <boost/thread/locks.hpp> |
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#include <boost/thread/condition_variable.hpp> |
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#include <vector> |
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#include <algorithm> |
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template<typename T> class CCheckQueueControl; |
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/** Queue for verifications that have to be performed.
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* The verifications are represented by a type T, which must provide an |
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* operator(), returning a bool. |
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* |
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* One thread (the master) is assumed to push batches of verifications |
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* onto the queue, where they are processed by N-1 worker threads. When |
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* the master is done adding work, it temporarily joins the worker pool |
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* as an N'th worker, until all jobs are done. |
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*/ |
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template<typename T> class CCheckQueue { |
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private: |
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// Mutex to protect the inner state
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boost::mutex mutex; |
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// Worker threads block on this when out of work
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boost::condition_variable condWorker; |
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// Master thread blocks on this when out of work
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boost::condition_variable condMaster; |
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// Quit method blocks on this until all workers are gone
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boost::condition_variable condQuit; |
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// The queue of elements to be processed.
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// As the order of booleans doesn't matter, it is used as a LIFO (stack)
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std::vector<T> queue; |
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// The number of workers (including the master) that are idle.
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int nIdle; |
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// The total number of workers (including the master).
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int nTotal; |
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// The temporary evaluation result.
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bool fAllOk; |
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// Number of verifications that haven't completed yet.
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// This includes elements that are not anymore in queue, but still in
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// worker's own batches.
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unsigned int nTodo; |
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// Whether we're shutting down.
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bool fQuit; |
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// The maximum number of elements to be processed in one batch
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unsigned int nBatchSize; |
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// Internal function that does bulk of the verification work.
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bool Loop(bool fMaster = false) { |
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boost::condition_variable &cond = fMaster ? condMaster : condWorker; |
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std::vector<T> vChecks; |
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vChecks.reserve(nBatchSize); |
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unsigned int nNow = 0; |
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bool fOk = true; |
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do { |
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{ |
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boost::unique_lock<boost::mutex> lock(mutex); |
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// first do the clean-up of the previous loop run (allowing us to do it in the same critsect)
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if (nNow) { |
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fAllOk &= fOk; |
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nTodo -= nNow; |
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if (nTodo == 0 && !fMaster) |
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// We processed the last element; inform the master he can exit and return the result
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condMaster.notify_one(); |
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} else { |
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// first iteration
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nTotal++; |
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} |
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// logically, the do loop starts here
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while (queue.empty()) { |
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if ((fMaster || fQuit) && nTodo == 0) { |
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nTotal--; |
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if (nTotal==0) |
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condQuit.notify_one(); |
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bool fRet = fAllOk; |
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// reset the status for new work later
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if (fMaster) |
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fAllOk = true; |
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// return the current status
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return fRet; |
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} |
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nIdle++; |
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cond.wait(lock); // wait
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nIdle--; |
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} |
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// Decide how many work units to process now.
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// * Do not try to do everything at once, but aim for increasingly smaller batches so
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// all workers finish approximately simultaneously.
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// * Try to account for idle jobs which will instantly start helping.
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// * Don't do batches smaller than 1 (duh), or larger than nBatchSize.
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nNow = std::max(1U, std::min(nBatchSize, (unsigned int)queue.size() / (nTotal + nIdle + 1))); |
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vChecks.resize(nNow); |
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for (unsigned int i = 0; i < nNow; i++) { |
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// We want the lock on the mutex to be as short as possible, so swap jobs from the global
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// queue to the local batch vector instead of copying.
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vChecks[i].swap(queue.back()); |
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queue.pop_back(); |
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} |
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// Check whether we need to do work at all
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fOk = fAllOk; |
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} |
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// execute work
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BOOST_FOREACH(T &check, vChecks) |
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if (fOk) |
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fOk = check(); |
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vChecks.clear(); |
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} while(true); |
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} |
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public: |
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// Create a new check queue
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CCheckQueue(unsigned int nBatchSizeIn) : |
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nIdle(0), nTotal(0), fAllOk(true), nTodo(0), fQuit(false), nBatchSize(nBatchSizeIn) {} |
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// Worker thread
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void Thread() { |
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Loop(); |
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} |
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// Wait until execution finishes, and return whether all evaluations where succesful.
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bool Wait() { |
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return Loop(true); |
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} |
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// Add a batch of checks to the queue
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void Add(std::vector<T> &vChecks) { |
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boost::unique_lock<boost::mutex> lock(mutex); |
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BOOST_FOREACH(T &check, vChecks) { |
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queue.push_back(T()); |
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check.swap(queue.back()); |
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} |
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nTodo += vChecks.size(); |
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if (vChecks.size() == 1) |
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condWorker.notify_one(); |
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else if (vChecks.size() > 1) |
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condWorker.notify_all(); |
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} |
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// Shut the queue down
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void Quit() { |
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boost::unique_lock<boost::mutex> lock(mutex); |
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fQuit = true; |
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// No need to wake the master, as he will quit automatically when all jobs are
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// done.
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condWorker.notify_all(); |
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while (nTotal > 0) |
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condQuit.wait(lock); |
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} |
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friend class CCheckQueueControl<T>; |
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}; |
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/** RAII-style controller object for a CCheckQueue that guarantees the passed
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* queue is finished before continuing. |
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*/ |
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template<typename T> class CCheckQueueControl { |
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private: |
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CCheckQueue<T> *pqueue; |
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bool fDone; |
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public: |
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CCheckQueueControl(CCheckQueue<T> *pqueueIn) : pqueue(pqueueIn), fDone(false) { |
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// passed queue is supposed to be unused, or NULL
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if (pqueue != NULL) { |
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assert(pqueue->nTotal == pqueue->nIdle); |
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assert(pqueue->nTodo == 0); |
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assert(pqueue->fAllOk == true); |
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} |
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} |
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bool Wait() { |
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if (pqueue == NULL) |
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return true; |
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bool fRet = pqueue->Wait(); |
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fDone = true; |
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return fRet; |
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} |
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void Add(std::vector<T> &vChecks) { |
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if (pqueue != NULL) |
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pqueue->Add(vChecks); |
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} |
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~CCheckQueueControl() { |
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if (!fDone) |
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Wait(); |
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} |
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}; |
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#endif |
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