diff options
| -rw-r--r-- | src/txmempool.cpp | 23 | ||||
| -rw-r--r-- | src/txmempool.h | 52 |
2 files changed, 73 insertions, 2 deletions
diff --git a/src/txmempool.cpp b/src/txmempool.cpp index 441255182e..64b91d6296 100644 --- a/src/txmempool.cpp +++ b/src/txmempool.cpp @@ -23,7 +23,7 @@ CTxMemPoolEntry::CTxMemPoolEntry(const CTransactionRef& _tx, const CAmount& _nFe int64_t _nTime, unsigned int _entryHeight, bool _spendsCoinbase, int64_t _sigOpsCost, LockPoints lp) : tx(_tx), nFee(_nFee), nTxWeight(GetTransactionWeight(*tx)), nUsageSize(RecursiveDynamicUsage(tx)), nTime(_nTime), entryHeight(_entryHeight), - spendsCoinbase(_spendsCoinbase), sigOpCost(_sigOpsCost), lockPoints(lp) + spendsCoinbase(_spendsCoinbase), sigOpCost(_sigOpsCost), lockPoints(lp), m_epoch(0) { nCountWithDescendants = 1; nSizeWithDescendants = GetTxSize(); @@ -325,7 +325,7 @@ void CTxMemPoolEntry::UpdateAncestorState(int64_t modifySize, CAmount modifyFee, } CTxMemPool::CTxMemPool(CBlockPolicyEstimator* estimator) - : nTransactionsUpdated(0), minerPolicyEstimator(estimator) + : nTransactionsUpdated(0), minerPolicyEstimator(estimator), m_epoch(0), m_has_epoch_guard(false) { _clear(); //lock free clear @@ -1105,4 +1105,23 @@ void CTxMemPool::SetIsLoaded(bool loaded) m_is_loaded = loaded; } + +CTxMemPool::EpochGuard CTxMemPool::GetFreshEpoch() const +{ + return EpochGuard(*this); +} +CTxMemPool::EpochGuard::EpochGuard(const CTxMemPool& in) : pool(in) +{ + assert(!pool.m_has_epoch_guard); + ++pool.m_epoch; + pool.m_has_epoch_guard = true; +} + +CTxMemPool::EpochGuard::~EpochGuard() +{ + // prevents stale results being used + ++pool.m_epoch; + pool.m_has_epoch_guard = false; +} + SaltedTxidHasher::SaltedTxidHasher() : k0(GetRand(std::numeric_limits<uint64_t>::max())), k1(GetRand(std::numeric_limits<uint64_t>::max())) {} diff --git a/src/txmempool.h b/src/txmempool.h index e9f1f1c8a1..a9551706ed 100644 --- a/src/txmempool.h +++ b/src/txmempool.h @@ -129,6 +129,7 @@ public: int64_t GetSigOpCostWithAncestors() const { return nSigOpCostWithAncestors; } mutable size_t vTxHashesIdx; //!< Index in mempool's vTxHashes + mutable uint64_t m_epoch; //!< epoch when last touched, useful for graph algorithms }; // Helpers for modifying CTxMemPool::mapTx, which is a boost multi_index. @@ -453,6 +454,8 @@ private: mutable int64_t lastRollingFeeUpdate; mutable bool blockSinceLastRollingFeeBump; mutable double rollingMinimumFeeRate; //!< minimum fee to get into the pool, decreases exponentially + mutable uint64_t m_epoch; + mutable bool m_has_epoch_guard; void trackPackageRemoved(const CFeeRate& rate) EXCLUSIVE_LOCKS_REQUIRED(cs); @@ -736,6 +739,55 @@ private: * removal. */ void removeUnchecked(txiter entry, MemPoolRemovalReason reason) EXCLUSIVE_LOCKS_REQUIRED(cs); +public: + /** EpochGuard: RAII-style guard for using epoch-based graph traversal algorithms. + * When walking ancestors or descendants, we generally want to avoid + * visiting the same transactions twice. Some traversal algorithms use + * std::set (or setEntries) to deduplicate the transaction we visit. + * However, use of std::set is algorithmically undesirable because it both + * adds an asymptotic factor of O(log n) to traverals cost and triggers O(n) + * more dynamic memory allocations. + * In many algorithms we can replace std::set with an internal mempool + * counter to track the time (or, "epoch") that we began a traversal, and + * check + update a per-transaction epoch for each transaction we look at to + * determine if that transaction has not yet been visited during the current + * traversal's epoch. + * Algorithms using std::set can be replaced on a one by one basis. + * Both techniques are not fundamentally incomaptible across the codebase. + * Generally speaking, however, the remaining use of std::set for mempool + * traversal should be viewed as a TODO for replacement with an epoch based + * traversal, rather than a preference for std::set over epochs in that + * algorithm. + */ + class EpochGuard { + const CTxMemPool& pool; + public: + EpochGuard(const CTxMemPool& in); + ~EpochGuard(); + }; + // N.B. GetFreshEpoch modifies mutable state via the EpochGuard construction + // (and later destruction) + EpochGuard GetFreshEpoch() const EXCLUSIVE_LOCKS_REQUIRED(cs); + + /** visited marks a CTxMemPoolEntry as having been traversed + * during the lifetime of the most recently created EpochGuard + * and returns false if we are the first visitor, true otherwise. + * + * An EpochGuard must be held when visited is called or an assert will be + * triggered. + * + */ + bool visited(txiter it) const EXCLUSIVE_LOCKS_REQUIRED(cs) { + assert(m_has_epoch_guard); + bool ret = it->m_epoch >= m_epoch; + it->m_epoch = std::max(it->m_epoch, m_epoch); + return ret; + } + + bool visited(Optional<txiter> it) const EXCLUSIVE_LOCKS_REQUIRED(cs) { + assert(m_has_epoch_guard); + return !it || visited(*it); + } }; /** |