TxMemPool: Change mapTx to a boost::multi_index_container

Indexes on:
- Tx Hash
- Fee Rate (fee-per-kb)

src/miner.cpp

@@ -158,10 +158,10 @@ CBlockTemplate* CreateNewBlock(const CScript& scriptPubKeyIn)
         // This vector will be sorted into a priority queue:
         vector<TxPriority> vecPriority;
         vecPriority.reserve(mempool.mapTx.size());
-        for (map<uint256, CTxMemPoolEntry>::iterator mi = mempool.mapTx.begin();
+        for (CTxMemPool::indexed_transaction_set::iterator mi = mempool.mapTx.begin();
              mi != mempool.mapTx.end(); ++mi)
         {
-            const CTransaction& tx = mi->second.GetTx();
+            const CTransaction& tx = mi->GetTx();
             if (tx.IsCoinBase() || !IsFinalTx(tx, nHeight, pblock->nTime))
                 continue;
 
@@ -196,7 +196,7 @@ CBlockTemplate* CreateNewBlock(const CScript& scriptPubKeyIn)
                     }
                     mapDependers[txin.prevout.hash].push_back(porphan);
                     porphan->setDependsOn.insert(txin.prevout.hash);
-                    nTotalIn += mempool.mapTx[txin.prevout.hash].GetTx().vout[txin.prevout.n].nValue;
+                    nTotalIn += mempool.mapTx.find(txin.prevout.hash)->GetTx().vout[txin.prevout.n].nValue;
                     continue;
                 }
                 const CCoins* coins = view.AccessCoins(txin.prevout.hash);
@@ -226,7 +226,7 @@ CBlockTemplate* CreateNewBlock(const CScript& scriptPubKeyIn)
                 porphan->feeRate = feeRate;
             }
             else
-                vecPriority.push_back(TxPriority(dPriority, feeRate, &mi->second.GetTx()));
+                vecPriority.push_back(TxPriority(dPriority, feeRate, &(mi->GetTx())));
         }
 
         // Collect transactions into block

src/rpcblockchain.cpp

@@ -181,10 +181,9 @@ UniValue mempoolToJSON(bool fVerbose = false)
     {
         LOCK(mempool.cs);
         UniValue o(UniValue::VOBJ);
-        BOOST_FOREACH(const PAIRTYPE(uint256, CTxMemPoolEntry)& entry, mempool.mapTx)
+        BOOST_FOREACH(const CTxMemPoolEntry& e, mempool.mapTx)
         {
-            const uint256& hash = entry.first;
-            const CTxMemPoolEntry& e = entry.second;
+            const uint256& hash = e.GetTx().GetHash();
             UniValue info(UniValue::VOBJ);
             info.push_back(Pair("size", (int)e.GetTxSize()));
             info.push_back(Pair("fee", ValueFromAmount(e.GetFee())));

src/test/mempool_tests.cpp

@@ -100,4 +100,56 @@ BOOST_AUTO_TEST_CASE(MempoolRemoveTest)
     removed.clear();
 }
 
+BOOST_AUTO_TEST_CASE(MempoolIndexingTest)
+{
+    CTxMemPool pool(CFeeRate(0));
+
+    /* 3rd highest fee */
+    CMutableTransaction tx1 = CMutableTransaction();
+    tx1.vout.resize(1);
+    tx1.vout[0].scriptPubKey = CScript() << OP_11 << OP_EQUAL;
+    tx1.vout[0].nValue = 10 * COIN;
+    pool.addUnchecked(tx1.GetHash(), CTxMemPoolEntry(tx1, 10000LL, 0, 10.0, 1, true));
+
+    /* highest fee */
+    CMutableTransaction tx2 = CMutableTransaction();
+    tx2.vout.resize(1);
+    tx2.vout[0].scriptPubKey = CScript() << OP_11 << OP_EQUAL;
+    tx2.vout[0].nValue = 2 * COIN;
+    pool.addUnchecked(tx2.GetHash(), CTxMemPoolEntry(tx2, 20000LL, 0, 9.0, 1, true));
+
+    /* lowest fee */
+    CMutableTransaction tx3 = CMutableTransaction();
+    tx3.vout.resize(1);
+    tx3.vout[0].scriptPubKey = CScript() << OP_11 << OP_EQUAL;
+    tx3.vout[0].nValue = 5 * COIN;
+    pool.addUnchecked(tx3.GetHash(), CTxMemPoolEntry(tx3, 0LL, 0, 100.0, 1, true));
+
+    /* 2nd highest fee */
+    CMutableTransaction tx4 = CMutableTransaction();
+    tx4.vout.resize(1);
+    tx4.vout[0].scriptPubKey = CScript() << OP_11 << OP_EQUAL;
+    tx4.vout[0].nValue = 6 * COIN;
+    pool.addUnchecked(tx4.GetHash(), CTxMemPoolEntry(tx4, 15000LL, 0, 1.0, 1, true));
+
+    /* equal fee rate to tx1, but newer */
+    CMutableTransaction tx5 = CMutableTransaction();
+    tx5.vout.resize(1);
+    tx5.vout[0].scriptPubKey = CScript() << OP_11 << OP_EQUAL;
+    tx5.vout[0].nValue = 11 * COIN;
+    pool.addUnchecked(tx5.GetHash(), CTxMemPoolEntry(tx5, 10000LL, 1, 10.0, 1, true));
+
+    // there should be 4 transactions in the mempool
+    BOOST_CHECK_EQUAL(pool.size(), 5);
+
+    // Check the fee-rate index is in order, should be tx2, tx4, tx1, tx5, tx3
+    CTxMemPool::indexed_transaction_set::nth_index<1>::type::iterator it = pool.mapTx.get<1>().begin();
+    BOOST_CHECK_EQUAL(it++->GetTx().GetHash().ToString(), tx2.GetHash().ToString());
+    BOOST_CHECK_EQUAL(it++->GetTx().GetHash().ToString(), tx4.GetHash().ToString());
+    BOOST_CHECK_EQUAL(it++->GetTx().GetHash().ToString(), tx1.GetHash().ToString());
+    BOOST_CHECK_EQUAL(it++->GetTx().GetHash().ToString(), tx5.GetHash().ToString());
+    BOOST_CHECK_EQUAL(it++->GetTx().GetHash().ToString(), tx3.GetHash().ToString());
+    BOOST_CHECK(it == pool.mapTx.get<1>().end());
+}
+
 BOOST_AUTO_TEST_SUITE_END()

src/txmempool.cpp

@@ -32,6 +32,7 @@ CTxMemPoolEntry::CTxMemPoolEntry(const CTransaction& _tx, const CAmount& _nFee,
     nTxSize = ::GetSerializeSize(tx, SER_NETWORK, PROTOCOL_VERSION);
     nModSize = tx.CalculateModifiedSize(nTxSize);
     nUsageSize = RecursiveDynamicUsage(tx);
+    feeRate = CFeeRate(nFee, nTxSize);
 }
 
 CTxMemPoolEntry::CTxMemPoolEntry(const CTxMemPoolEntry& other)
@@ -96,8 +97,8 @@ bool CTxMemPool::addUnchecked(const uint256& hash, const CTxMemPoolEntry &entry,
     // Used by main.cpp AcceptToMemoryPool(), which DOES do
     // all the appropriate checks.
     LOCK(cs);
-    mapTx[hash] = entry;
-    const CTransaction& tx = mapTx[hash].GetTx();
+    mapTx.insert(entry);
+    const CTransaction& tx = mapTx.find(hash)->GetTx();
     for (unsigned int i = 0; i < tx.vin.size(); i++)
         mapNextTx[tx.vin[i].prevout] = CInPoint(&tx, i);
     nTransactionsUpdated++;
@@ -134,7 +135,7 @@ void CTxMemPool::remove(const CTransaction &origTx, std::list<CTransaction>& rem
             txToRemove.pop_front();
             if (!mapTx.count(hash))
                 continue;
-            const CTransaction& tx = mapTx[hash].GetTx();
+            const CTransaction& tx = mapTx.find(hash)->GetTx();
             if (fRecursive) {
                 for (unsigned int i = 0; i < tx.vout.size(); i++) {
                     std::map<COutPoint, CInPoint>::iterator it = mapNextTx.find(COutPoint(hash, i));
@@ -147,8 +148,8 @@ void CTxMemPool::remove(const CTransaction &origTx, std::list<CTransaction>& rem
                 mapNextTx.erase(txin.prevout);
 
             removed.push_back(tx);
-            totalTxSize -= mapTx[hash].GetTxSize();
-            cachedInnerUsage -= mapTx[hash].DynamicMemoryUsage();
+            totalTxSize -= mapTx.find(hash)->GetTxSize();
+            cachedInnerUsage -= mapTx.find(hash)->DynamicMemoryUsage();
             mapTx.erase(hash);
             nTransactionsUpdated++;
             minerPolicyEstimator->removeTx(hash);
@@ -161,10 +162,10 @@ void CTxMemPool::removeCoinbaseSpends(const CCoinsViewCache *pcoins, unsigned in
     // Remove transactions spending a coinbase which are now immature
     LOCK(cs);
     list<CTransaction> transactionsToRemove;
-    for (std::map<uint256, CTxMemPoolEntry>::const_iterator it = mapTx.begin(); it != mapTx.end(); it++) {
-        const CTransaction& tx = it->second.GetTx();
+    for (indexed_transaction_set::const_iterator it = mapTx.begin(); it != mapTx.end(); it++) {
+        const CTransaction& tx = it->GetTx();
         BOOST_FOREACH(const CTxIn& txin, tx.vin) {
-            std::map<uint256, CTxMemPoolEntry>::const_iterator it2 = mapTx.find(txin.prevout.hash);
+            indexed_transaction_set::const_iterator it2 = mapTx.find(txin.prevout.hash);
             if (it2 != mapTx.end())
                 continue;
             const CCoins *coins = pcoins->AccessCoins(txin.prevout.hash);
@@ -209,8 +210,10 @@ void CTxMemPool::removeForBlock(const std::vector<CTransaction>& vtx, unsigned i
     BOOST_FOREACH(const CTransaction& tx, vtx)
     {
         uint256 hash = tx.GetHash();
-        if (mapTx.count(hash))
-            entries.push_back(mapTx[hash]);
+
+        indexed_transaction_set::iterator i = mapTx.find(hash);
+        if (i != mapTx.end())
+            entries.push_back(*i);
     }
     BOOST_FOREACH(const CTransaction& tx, vtx)
     {
@@ -247,17 +250,17 @@ void CTxMemPool::check(const CCoinsViewCache *pcoins) const
 
     LOCK(cs);
     list<const CTxMemPoolEntry*> waitingOnDependants;
-    for (std::map<uint256, CTxMemPoolEntry>::const_iterator it = mapTx.begin(); it != mapTx.end(); it++) {
+    for (indexed_transaction_set::const_iterator it = mapTx.begin(); it != mapTx.end(); it++) {
         unsigned int i = 0;
-        checkTotal += it->second.GetTxSize();
-        innerUsage += it->second.DynamicMemoryUsage();
-        const CTransaction& tx = it->second.GetTx();
+        checkTotal += it->GetTxSize();
+        innerUsage += it->DynamicMemoryUsage();
+        const CTransaction& tx = it->GetTx();
         bool fDependsWait = false;
         BOOST_FOREACH(const CTxIn &txin, tx.vin) {
             // Check that every mempool transaction's inputs refer to available coins, or other mempool tx's.
-            std::map<uint256, CTxMemPoolEntry>::const_iterator it2 = mapTx.find(txin.prevout.hash);
+            indexed_transaction_set::const_iterator it2 = mapTx.find(txin.prevout.hash);
             if (it2 != mapTx.end()) {
-                const CTransaction& tx2 = it2->second.GetTx();
+                const CTransaction& tx2 = it2->GetTx();
                 assert(tx2.vout.size() > txin.prevout.n && !tx2.vout[txin.prevout.n].IsNull());
                 fDependsWait = true;
             } else {
@@ -272,7 +275,7 @@ void CTxMemPool::check(const CCoinsViewCache *pcoins) const
             i++;
         }
         if (fDependsWait)
-            waitingOnDependants.push_back(&it->second);
+            waitingOnDependants.push_back(&(*it));
         else {
             CValidationState state;
             assert(CheckInputs(tx, state, mempoolDuplicate, false, 0, false, NULL));
@@ -296,8 +299,8 @@ void CTxMemPool::check(const CCoinsViewCache *pcoins) const
     }
     for (std::map<COutPoint, CInPoint>::const_iterator it = mapNextTx.begin(); it != mapNextTx.end(); it++) {
         uint256 hash = it->second.ptx->GetHash();
-        map<uint256, CTxMemPoolEntry>::const_iterator it2 = mapTx.find(hash);
-        const CTransaction& tx = it2->second.GetTx();
+        indexed_transaction_set::const_iterator it2 = mapTx.find(hash);
+        const CTransaction& tx = it2->GetTx();
         assert(it2 != mapTx.end());
         assert(&tx == it->second.ptx);
         assert(tx.vin.size() > it->second.n);
@@ -314,16 +317,16 @@ void CTxMemPool::queryHashes(vector<uint256>& vtxid)
 
     LOCK(cs);
     vtxid.reserve(mapTx.size());
-    for (map<uint256, CTxMemPoolEntry>::iterator mi = mapTx.begin(); mi != mapTx.end(); ++mi)
-        vtxid.push_back((*mi).first);
+    for (indexed_transaction_set::iterator mi = mapTx.begin(); mi != mapTx.end(); ++mi)
+        vtxid.push_back(mi->GetTx().GetHash());
 }
 
 bool CTxMemPool::lookup(uint256 hash, CTransaction& result) const
 {
     LOCK(cs);
-    map<uint256, CTxMemPoolEntry>::const_iterator i = mapTx.find(hash);
+    indexed_transaction_set::const_iterator i = mapTx.find(hash);
     if (i == mapTx.end()) return false;
-    result = i->second.GetTx();
+    result = i->GetTx();
     return true;
 }
 
@@ -429,5 +432,6 @@ bool CCoinsViewMemPool::HaveCoins(const uint256 &txid) const {
 
 size_t CTxMemPool::DynamicMemoryUsage() const {
     LOCK(cs);
-    return memusage::DynamicUsage(mapTx) + memusage::DynamicUsage(mapNextTx) + memusage::DynamicUsage(mapDeltas) + cachedInnerUsage;
+    // Estimate the overhead of mapTx to be 6 pointers + an allocation, as no exact formula for boost::multi_index_contained is implemented.
+    return memusage::MallocUsage(sizeof(CTxMemPoolEntry) + 6 * sizeof(void*)) * mapTx.size() + memusage::DynamicUsage(mapNextTx) + memusage::DynamicUsage(mapDeltas) + cachedInnerUsage;
 }

src/txmempool.h

@@ -13,6 +13,10 @@
 #include "primitives/transaction.h"
 #include "sync.h"
 
+#undef foreach
+#include "boost/multi_index_container.hpp"
+#include "boost/multi_index/ordered_index.hpp"
+
 class CAutoFile;
 
 inline double AllowFreeThreshold()
@@ -41,6 +45,7 @@ private:
     size_t nTxSize; //! ... and avoid recomputing tx size
     size_t nModSize; //! ... and modified size for priority
     size_t nUsageSize; //! ... and total memory usage
+    CFeeRate feeRate; //! ... and fee per kB
     int64_t nTime; //! Local time when entering the mempool
     double dPriority; //! Priority when entering the mempool
     unsigned int nHeight; //! Chain height when entering the mempool
@@ -55,6 +60,7 @@ public:
     const CTransaction& GetTx() const { return this->tx; }
     double GetPriority(unsigned int currentHeight) const;
     CAmount GetFee() const { return nFee; }
+    CFeeRate GetFeeRate() const { return feeRate; }
     size_t GetTxSize() const { return nTxSize; }
     int64_t GetTime() const { return nTime; }
     unsigned int GetHeight() const { return nHeight; }
@@ -62,6 +68,27 @@ public:
     size_t DynamicMemoryUsage() const { return nUsageSize; }
 };
 
+// extracts a TxMemPoolEntry's transaction hash
+struct mempoolentry_txid
+{
+    typedef uint256 result_type;
+    result_type operator() (const CTxMemPoolEntry &entry) const
+    {
+        return entry.GetTx().GetHash();
+    }
+};
+
+class CompareTxMemPoolEntryByFee
+{
+public:
+    bool operator()(const CTxMemPoolEntry& a, const CTxMemPoolEntry& b)
+    {
+        if (a.GetFeeRate() == b.GetFeeRate())
+            return a.GetTime() < b.GetTime();
+        return a.GetFeeRate() > b.GetFeeRate();
+    }
+};
+
 class CBlockPolicyEstimator;
 
 /** An inpoint - a combination of a transaction and an index n into its vin */
@@ -99,8 +126,21 @@ private:
     uint64_t cachedInnerUsage; //! sum of dynamic memory usage of all the map elements (NOT the maps themselves)
 
 public:
+    typedef boost::multi_index_container<
+        CTxMemPoolEntry,
+        boost::multi_index::indexed_by<
+            // sorted by txid
+            boost::multi_index::ordered_unique<mempoolentry_txid>,
+            // sorted by fee rate
+            boost::multi_index::ordered_non_unique<
+                boost::multi_index::identity<CTxMemPoolEntry>,
+                CompareTxMemPoolEntryByFee
+            >
+        >
+    > indexed_transaction_set;
+
     mutable CCriticalSection cs;
-    std::map<uint256, CTxMemPoolEntry> mapTx;
+    indexed_transaction_set mapTx;
     std::map<COutPoint, CInPoint> mapNextTx;
     std::map<uint256, std::pair<double, CAmount> > mapDeltas;