Merge branch 'smartfee_wallet'

18 files changed, 179 insertions, 107 deletions

diff --git a/doc/release-notes.md b/doc/release-notes.md
index 3a4079e437..66059800b6 100644
--- a/doc/release-notes.md
+++ b/doc/release-notes.md
@@ -1,6 +1,26 @@
 (note: this is a temporary file, to be added-to by anybody, and moved to
 release-notes at release time)
 
+Transaction fee changes
+=======================
+
+This release automatically estimates how high a transaction fee (or how
+high a priority) transactions require to be confirmed quickly. The default
+settings will create transactions that confirm quickly; see the new
+'txconfirmtarget' setting to control the tradeoff between fees and
+confirmation times.
+
+Prior releases used hard-coded fees (and priorities), and would
+sometimes create transactions that took a very long time to confirm.
+
+
+New Command Line Options
+========================
+
+-txconfirmtarget=n : create transactions that have enough fees (or priority)
+so they are likely to confirm within n blocks (default: 1). This setting
+is over-ridden by the -paytxfee option.
+
 New RPC methods
 ===============
 
diff --git a/src/core.cpp b/src/core.cpp
index ca28624529..47f3b2a015 100644
--- a/src/core.cpp
+++ b/src/core.cpp
@@ -80,7 +80,7 @@ CFeeRate::CFeeRate(int64_t nFeePaid, size_t nSize)
         nSatoshisPerK = 0;
 }
 
-int64_t CFeeRate::GetFee(size_t nSize)
+int64_t CFeeRate::GetFee(size_t nSize) const
 {
     return nSatoshisPerK*nSize / 1000;
 }
diff --git a/src/core.h b/src/core.h
index 8606831575..0387336c98 100644
--- a/src/core.h
+++ b/src/core.h
@@ -125,13 +125,14 @@ public:
     CFeeRate(int64_t nFeePaid, size_t nSize);
     CFeeRate(const CFeeRate& other) { nSatoshisPerK = other.nSatoshisPerK; }
 
-    int64_t GetFee(size_t size); // unit returned is satoshis
-    int64_t GetFeePerK() { return GetFee(1000); } // satoshis-per-1000-bytes
+    int64_t GetFee(size_t size) const; // unit returned is satoshis
+    int64_t GetFeePerK() const { return GetFee(1000); } // satoshis-per-1000-bytes
 
     friend bool operator<(const CFeeRate& a, const CFeeRate& b) { return a.nSatoshisPerK < b.nSatoshisPerK; }
     friend bool operator>(const CFeeRate& a, const CFeeRate& b) { return a.nSatoshisPerK > b.nSatoshisPerK; }
     friend bool operator==(const CFeeRate& a, const CFeeRate& b) { return a.nSatoshisPerK == b.nSatoshisPerK; }
-
+    friend bool operator<=(const CFeeRate& a, const CFeeRate& b) { return a.nSatoshisPerK <= b.nSatoshisPerK; }
+    friend bool operator>=(const CFeeRate& a, const CFeeRate& b) { return a.nSatoshisPerK >= b.nSatoshisPerK; }
     std::string ToString() const;
 
     IMPLEMENT_SERIALIZE( READWRITE(nSatoshisPerK); )
@@ -216,8 +217,6 @@ private:
     void UpdateHash() const;
 
 public:
-    static CFeeRate minTxFee;
-    static CFeeRate minRelayTxFee;
     static const int CURRENT_VERSION=1;
 
     // The local variables are made const to prevent unintended modification
diff --git a/src/init.cpp b/src/init.cpp
index 2dd141a735..5afae32327 100644
--- a/src/init.cpp
+++ b/src/init.cpp
@@ -253,14 +253,16 @@ std::string HelpMessage(HelpMessageMode mode)
 #ifdef ENABLE_WALLET
     strUsage += "\n" + _("Wallet options:") + "\n";
     strUsage += "  -disablewallet         " + _("Do not load the wallet and disable wallet RPC calls") + "\n";
+    strUsage += "  -mintxfee=<amt>        " + strprintf(_("Fees (in BTC/Kb) smaller than this are considered zero fee for transaction creation (default: %s)"), FormatMoney(CWallet::minTxFee.GetFeePerK())) + "\n";
     strUsage += "  -paytxfee=<amt>        " + strprintf(_("Fee (in BTC/kB) to add to transactions you send (default: %s)"), FormatMoney(payTxFee.GetFeePerK())) + "\n";
     strUsage += "  -rescan                " + _("Rescan the block chain for missing wallet transactions") + " " + _("on startup") + "\n";
+    strUsage += "  -respendnotify=<cmd>   " + _("Execute command when a network tx respends wallet tx input (%s=respend TxID, %t=wallet TxID)") + "\n";
     strUsage += "  -salvagewallet         " + _("Attempt to recover private keys from a corrupt wallet.dat") + " " + _("on startup") + "\n";
     strUsage += "  -spendzeroconfchange   " + _("Spend unconfirmed change when sending transactions (default: 1)") + "\n";
+    strUsage += "  -txconfirmtarget=<n>   " + _("If paytxfee is not set, include enough fee so transactions are confirmed on average within n blocks (default: 1)") + "\n";
     strUsage += "  -upgradewallet         " + _("Upgrade wallet to latest format") + " " + _("on startup") + "\n";
     strUsage += "  -wallet=<file>         " + _("Specify wallet file (within data directory)") + " " + _("(default: wallet.dat)") + "\n";
     strUsage += "  -walletnotify=<cmd>    " + _("Execute command when a wallet transaction changes (%s in cmd is replaced by TxID)") + "\n";
-    strUsage += "  -respendnotify=<cmd>   " + _("Execute command when a network tx respends wallet tx input (%s=respend TxID, %t=wallet TxID)") + "\n";
     strUsage += "  -zapwallettxes=<mode>  " + _("Delete all wallet transactions and only recover those part of the blockchain through -rescan on startup") + "\n";
     strUsage += "                         " + _("(default: 1, 1 = keep tx meta data e.g. account owner and payment request information, 2 = drop tx meta data)") + "\n";
 #endif
@@ -294,8 +296,7 @@ std::string HelpMessage(HelpMessageMode mode)
         strUsage += "  -limitfreerelay=<n>    " + _("Continuously rate-limit free transactions to <n>*1000 bytes per minute (default:15)") + "\n";
         strUsage += "  -maxsigcachesize=<n>   " + _("Limit size of signature cache to <n> entries (default: 50000)") + "\n";
     }
-    strUsage += "  -mintxfee=<amt>        " + strprintf(_("Fees (in BTC/Kb) smaller than this are considered zero fee for transaction creation (default: %s)"), FormatMoney(CTransaction::minTxFee.GetFeePerK())) + "\n";
-    strUsage += "  -minrelaytxfee=<amt>   " + strprintf(_("Fees (in BTC/Kb) smaller than this are considered zero fee for relaying (default: %s)"), FormatMoney(CTransaction::minRelayTxFee.GetFeePerK())) + "\n";
+    strUsage += "  -minrelaytxfee=<amt>   " + strprintf(_("Fees (in BTC/Kb) smaller than this are considered zero fee for relaying (default: %s)"), FormatMoney(::minRelayTxFee.GetFeePerK())) + "\n";
     strUsage += "  -printtoconsole        " + _("Send trace/debug info to console instead of debug.log file") + "\n";
     if (GetBoolArg("-help-debug", false))
     {
@@ -609,24 +610,24 @@ bool AppInit2(boost::thread_group& threadGroup)
     // a transaction spammer can cheaply fill blocks using
     // 1-satoshi-fee transactions. It should be set above the real
     // cost to you of processing a transaction.
-    if (mapArgs.count("-mintxfee"))
-    {
-        int64_t n = 0;
-        if (ParseMoney(mapArgs["-mintxfee"], n) && n > 0)
-            CTransaction::minTxFee = CFeeRate(n);
-        else
-            return InitError(strprintf(_("Invalid amount for -mintxfee=<amount>: '%s'"), mapArgs["-mintxfee"]));
-    }
     if (mapArgs.count("-minrelaytxfee"))
     {
         int64_t n = 0;
         if (ParseMoney(mapArgs["-minrelaytxfee"], n) && n > 0)
-            CTransaction::minRelayTxFee = CFeeRate(n);
+            ::minRelayTxFee = CFeeRate(n);
         else
             return InitError(strprintf(_("Invalid amount for -minrelaytxfee=<amount>: '%s'"), mapArgs["-minrelaytxfee"]));
     }
 
 #ifdef ENABLE_WALLET
+    if (mapArgs.count("-mintxfee"))
+    {
+        int64_t n = 0;
+        if (ParseMoney(mapArgs["-mintxfee"], n) && n > 0)
+            CWallet::minTxFee = CFeeRate(n);
+        else
+            return InitError(strprintf(_("Invalid amount for -mintxfee=<amount>: '%s'"), mapArgs["-mintxfee"]));
+    }
     if (mapArgs.count("-paytxfee"))
     {
         int64_t nFeePerK = 0;
@@ -635,7 +636,13 @@ bool AppInit2(boost::thread_group& threadGroup)
         if (nFeePerK > nHighTransactionFeeWarning)
             InitWarning(_("Warning: -paytxfee is set very high! This is the transaction fee you will pay if you send a transaction."));
         payTxFee = CFeeRate(nFeePerK, 1000);
+        if (payTxFee < ::minRelayTxFee)
+        {
+            return InitError(strprintf(_("Invalid amount for -paytxfee=<amount>: '%s' (must be at least %s)"),
+                                       mapArgs["-paytxfee"], ::minRelayTxFee.ToString()));
+        }
     }
+    nTxConfirmTarget = GetArg("-txconfirmtarget", 1);
     bSpendZeroConfChange = GetArg("-spendzeroconfchange", true);
 
     std::string strWalletFile = GetArg("-wallet", "wallet.dat");
diff --git a/src/main.cpp b/src/main.cpp
index 04d9523e26..54b926abdb 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -38,8 +38,6 @@ using namespace boost;
 
 CCriticalSection cs_main;
 
-CTxMemPool mempool;
-
 map<uint256, CBlockIndex*> mapBlockIndex;
 CChain chainActive;
 int64_t nTimeBestReceived = 0;
@@ -50,10 +48,10 @@ bool fBenchmark = false;
 bool fTxIndex = false;
 unsigned int nCoinCacheSize = 5000;
 
-/** Fees smaller than this (in satoshi) are considered zero fee (for transaction creation) */
-CFeeRate CTransaction::minTxFee = CFeeRate(10000);  // Override with -mintxfee
 /** Fees smaller than this (in satoshi) are considered zero fee (for relaying and mining) */
-CFeeRate CTransaction::minRelayTxFee = CFeeRate(1000);
+CFeeRate minRelayTxFee = CFeeRate(1000);
+
+CTxMemPool mempool(::minRelayTxFee);
 
 struct COrphanBlock {
     uint256 hashBlock;
@@ -617,7 +615,7 @@ bool IsStandardTx(const CTransaction& tx, string& reason)
         }
         if (whichType == TX_NULL_DATA)
             nDataOut++;
-        else if (txout.IsDust(CTransaction::minRelayTxFee)) {
+        else if (txout.IsDust(::minRelayTxFee)) {
             reason = "dust";
             return false;
         }
@@ -858,7 +856,7 @@ bool CheckTransaction(const CTransaction& tx, CValidationState &state)
     return true;
 }
 
-int64_t GetMinFee(const CTransaction& tx, unsigned int nBytes, bool fAllowFree, enum GetMinFee_mode mode)
+int64_t GetMinRelayFee(const CTransaction& tx, unsigned int nBytes, bool fAllowFree)
 {
     {
         LOCK(mempool.cs);
@@ -870,10 +868,7 @@ int64_t GetMinFee(const CTransaction& tx, unsigned int nBytes, bool fAllowFree,
             return 0;
     }
 
-    // Base fee is either minTxFee or minRelayTxFee
-    CFeeRate baseFeeRate = (mode == GMF_RELAY) ? tx.minRelayTxFee : tx.minTxFee;
-
-    int64_t nMinFee = baseFeeRate.GetFee(nBytes);
+    int64_t nMinFee = ::minRelayTxFee.GetFee(nBytes);
 
     if (fAllowFree)
     {
@@ -881,9 +876,7 @@ int64_t GetMinFee(const CTransaction& tx, unsigned int nBytes, bool fAllowFree,
         // * If we are relaying we allow transactions up to DEFAULT_BLOCK_PRIORITY_SIZE - 1000
         //   to be considered to fall into this category. We don't want to encourage sending
         //   multiple transactions instead of one big transaction to avoid fees.
-        // * If we are creating a transaction we allow transactions up to 1,000 bytes
-        //   to be considered safe and assume they can likely make it into this section.
-        if (nBytes < (mode == GMF_SEND ? 1000 : (DEFAULT_BLOCK_PRIORITY_SIZE - 1000)))
+        if (nBytes < (DEFAULT_BLOCK_PRIORITY_SIZE - 1000))
             nMinFee = 0;
     }
 
@@ -1005,7 +998,7 @@ bool AcceptToMemoryPool(CTxMemPool& pool, CValidationState &state, const CTransa
         unsigned int nSize = entry.GetTxSize();
 
         // Don't accept it if it can't get into a block
-        int64_t txMinFee = GetMinFee(tx, nSize, true, GMF_RELAY);
+        int64_t txMinFee = GetMinRelayFee(tx, nSize, true);
         if (fLimitFree && nFees < txMinFee)
             return state.DoS(0, error("AcceptToMemoryPool : not enough fees %s, %d < %d",
                                       hash.ToString(), nFees, txMinFee),
@@ -1014,7 +1007,7 @@ bool AcceptToMemoryPool(CTxMemPool& pool, CValidationState &state, const CTransa
         // Continuously rate-limit free (really, very-low-fee)transactions
         // This mitigates 'penny-flooding' -- sending thousands of free transactions just to
         // be annoying or make others' transactions take longer to confirm.
-        if (fLimitFree && nFees < CTransaction::minRelayTxFee.GetFee(nSize))
+        if (fLimitFree && nFees < ::minRelayTxFee.GetFee(nSize))
         {
             static double dFreeCount;
             static int64_t nLastFreeTime;
@@ -1027,10 +1020,10 @@ bool AcceptToMemoryPool(CTxMemPool& pool, CValidationState &state, const CTransa
             LogPrint("mempool", "Rate limit dFreeCount: %g => %g\n", dFreeCount, dFreeCount+nSize);
         }
 
-        if (fRejectInsaneFee && nFees > CTransaction::minRelayTxFee.GetFee(nSize) * 10000)
+        if (fRejectInsaneFee && nFees > ::minRelayTxFee.GetFee(nSize) * 10000)
             return error("AcceptToMemoryPool: : insane fees %s, %d > %d",
                          hash.ToString(),
-                         nFees, CTransaction::minRelayTxFee.GetFee(nSize) * 10000);
+                         nFees, ::minRelayTxFee.GetFee(nSize) * 10000);
 
         // Check against previous transactions
         // This is done last to help prevent CPU exhaustion denial-of-service attacks.
@@ -1134,10 +1127,10 @@ int CMerkleTx::GetBlocksToMaturity() const
 }
 
 
-bool CMerkleTx::AcceptToMemoryPool(bool fLimitFree)
+bool CMerkleTx::AcceptToMemoryPool(bool fLimitFree, bool fRejectInsaneFee)
 {
     CValidationState state;
-    return ::AcceptToMemoryPool(mempool, state, *this, fLimitFree, NULL);
+    return ::AcceptToMemoryPool(mempool, state, *this, fLimitFree, NULL, fRejectInsaneFee);
 }
 
 
diff --git a/src/main.h b/src/main.h
index 19f4469008..961f2e78af 100644
--- a/src/main.h
+++ b/src/main.h
@@ -93,6 +93,7 @@ extern bool fBenchmark;
 extern int nScriptCheckThreads;
 extern bool fTxIndex;
 extern unsigned int nCoinCacheSize;
+extern CFeeRate minRelayTxFee;
 
 // Minimum disk space required - used in CheckDiskSpace()
 static const uint64_t nMinDiskSpace = 52428800;
@@ -245,14 +246,7 @@ struct CDiskTxPos : public CDiskBlockPos
 };
 
 
-
-enum GetMinFee_mode
-{
-    GMF_RELAY,
-    GMF_SEND,
-};
-
-int64_t GetMinFee(const CTransaction& tx, unsigned int nBytes, bool fAllowFree, enum GetMinFee_mode mode);
+int64_t GetMinRelayFee(const CTransaction& tx, unsigned int nBytes, bool fAllowFree);
 
 //
 // Check transaction inputs, and make sure any
@@ -459,7 +453,7 @@ public:
     int GetDepthInMainChain() const { CBlockIndex *pindexRet; return GetDepthInMainChain(pindexRet); }
     bool IsInMainChain() const { CBlockIndex *pindexRet; return GetDepthInMainChainINTERNAL(pindexRet) > 0; }
     int GetBlocksToMaturity() const;
-    bool AcceptToMemoryPool(bool fLimitFree=true);
+    bool AcceptToMemoryPool(bool fLimitFree=true, bool fRejectInsaneFee=true);
 };
 
 
diff --git a/src/miner.cpp b/src/miner.cpp
index 69e53756e0..17918a1280 100644
--- a/src/miner.cpp
+++ b/src/miner.cpp
@@ -236,7 +236,7 @@ CBlockTemplate* CreateNewBlock(const CScript& scriptPubKeyIn)
             double dPriorityDelta = 0;
             int64_t nFeeDelta = 0;
             mempool.ApplyDeltas(hash, dPriorityDelta, nFeeDelta);
-            if (fSortedByFee && (dPriorityDelta <= 0) && (nFeeDelta <= 0) && (feeRate < CTransaction::minRelayTxFee) && (nBlockSize + nTxSize >= nBlockMinSize))
+            if (fSortedByFee && (dPriorityDelta <= 0) && (nFeeDelta <= 0) && (feeRate < ::minRelayTxFee) && (nBlockSize + nTxSize >= nBlockMinSize))
                 continue;
 
             // Prioritise by fee once past the priority size or we run out of high-priority
diff --git a/src/qt/coincontroldialog.cpp b/src/qt/coincontroldialog.cpp
index c6a6150392..e0a524a55e 100644
--- a/src/qt/coincontroldialog.cpp
+++ b/src/qt/coincontroldialog.cpp
@@ -16,6 +16,8 @@
 #include "main.h"
 #include "wallet.h"
 
+#include <boost/assign/list_of.hpp> // for 'map_list_of()'
+
 #include <QApplication>
 #include <QCheckBox>
 #include <QCursor>
@@ -400,23 +402,24 @@ void CoinControlDialog::viewItemChanged(QTreeWidgetItem* item, int column)
 }
 
 // return human readable label for priority number
-QString CoinControlDialog::getPriorityLabel(double dPriority)
+QString CoinControlDialog::getPriorityLabel(const CTxMemPool& pool, double dPriority)
 {
-    if (AllowFree(dPriority)) // at least medium
+    // confirmations -> textual description
+    typedef std::map<unsigned int, QString> PriorityDescription;
+    const static PriorityDescription priorityDescriptions = boost::assign::map_list_of
+        (1, tr("highest"))(2, tr("higher"))(3, tr("high"))
+        (5, tr("medium-high"))(6, tr("medium"))
+        (10, tr("low-medium"))(15, tr("low"))
+        (20, tr("lower"));
+
+    BOOST_FOREACH(const PriorityDescription::value_type& i, priorityDescriptions)
     {
-        if      (AllowFree(dPriority / 1000000))  return tr("highest");
-        else if (AllowFree(dPriority / 100000))   return tr("higher");
-        else if (AllowFree(dPriority / 10000))    return tr("high");
-        else if (AllowFree(dPriority / 1000))     return tr("medium-high");
-        else                                      return tr("medium");
-    }
-    else
-    {
-        if      (AllowFree(dPriority * 10))   return tr("low-medium");
-        else if (AllowFree(dPriority * 100))  return tr("low");
-        else if (AllowFree(dPriority * 1000)) return tr("lower");
-        else                                  return tr("lowest");
+        double p = mempool.estimatePriority(i.first);
+        if (p > 0 && dPriority >= p) return i.second;
     }
+    // Note: if mempool hasn't accumulated enough history (estimatePriority
+    // returns -1) we're conservative and classify as "lowest"
+    return tr("lowest");
 }
 
 // shows count of locked unspent outputs
@@ -449,7 +452,7 @@ void CoinControlDialog::updateLabels(WalletModel *model, QDialog* dialog)
         {
             CTxOut txout(amount, (CScript)vector<unsigned char>(24, 0));
             txDummy.vout.push_back(txout);
-            if (txout.IsDust(CTransaction::minRelayTxFee))
+            if (txout.IsDust(::minRelayTxFee))
                fDust = true;
         }
     }
@@ -518,15 +521,20 @@ void CoinControlDialog::updateLabels(WalletModel *model, QDialog* dialog)
 
         // Priority
         dPriority = dPriorityInputs / (nBytes - nBytesInputs + (nQuantityUncompressed * 29)); // 29 = 180 - 151 (uncompressed public keys are over the limit. max 151 bytes of the input are ignored for priority)
-        sPriorityLabel = CoinControlDialog::getPriorityLabel(dPriority);
+        sPriorityLabel = CoinControlDialog::getPriorityLabel(mempool, dPriority);
 
         // Fee
         int64_t nFee = payTxFee.GetFee(max((unsigned int)1000, nBytes));
 
         // Min Fee
-        int64_t nMinFee = GetMinFee(txDummy, nBytes, AllowFree(dPriority), GMF_SEND);
+        nPayFee = CWallet::GetMinimumFee(nBytes, nTxConfirmTarget, mempool);
+
+        double dPriorityNeeded = mempool.estimatePriority(nTxConfirmTarget);
+        if (dPriorityNeeded <= 0) // Not enough mempool history: never send free
+            dPriorityNeeded = std::numeric_limits<double>::max();
 
-        nPayFee = max(nFee, nMinFee);
+        if (nBytes <= MAX_FREE_TRANSACTION_CREATE_SIZE && dPriority >= dPriorityNeeded)
+            nPayFee = 0;
 
         if (nPayAmount > 0)
         {
@@ -536,7 +544,7 @@ void CoinControlDialog::updateLabels(WalletModel *model, QDialog* dialog)
             if (nChange > 0 && nChange < CENT)
             {
                 CTxOut txout(nChange, (CScript)vector<unsigned char>(24, 0));
-                if (txout.IsDust(CTransaction::minRelayTxFee))
+                if (txout.IsDust(::minRelayTxFee))
                 {
                     nPayFee += nChange;
                     nChange = 0;
@@ -591,23 +599,23 @@ void CoinControlDialog::updateLabels(WalletModel *model, QDialog* dialog)
     }
 
     // turn labels "red"
-    l5->setStyleSheet((nBytes >= 1000) ? "color:red;" : "");                            // Bytes >= 1000
+    l5->setStyleSheet((nBytes >= MAX_FREE_TRANSACTION_CREATE_SIZE) ? "color:red;" : "");// Bytes >= 1000
     l6->setStyleSheet((dPriority > 0 && !AllowFree(dPriority)) ? "color:red;" : "");    // Priority < "medium"
     l7->setStyleSheet((fDust) ? "color:red;" : "");                                     // Dust = "yes"
 
     // tool tips
     QString toolTip1 = tr("This label turns red, if the transaction size is greater than 1000 bytes.") + "<br /><br />";
-    toolTip1 += tr("This means a fee of at least %1 per kB is required.").arg(BitcoinUnits::formatWithUnit(nDisplayUnit, CTransaction::minTxFee.GetFeePerK())) + "<br /><br />";
+    toolTip1 += tr("This means a fee of at least %1 per kB is required.").arg(BitcoinUnits::formatWithUnit(nDisplayUnit, CWallet::minTxFee.GetFeePerK())) + "<br /><br />";
     toolTip1 += tr("Can vary +/- 1 byte per input.");
 
     QString toolTip2 = tr("Transactions with higher priority are more likely to get included into a block.") + "<br /><br />";
     toolTip2 += tr("This label turns red, if the priority is smaller than \"medium\".") + "<br /><br />";
-    toolTip2 += tr("This means a fee of at least %1 per kB is required.").arg(BitcoinUnits::formatWithUnit(nDisplayUnit, CTransaction::minTxFee.GetFeePerK()));
+    toolTip2 += tr("This means a fee of at least %1 per kB is required.").arg(BitcoinUnits::formatWithUnit(nDisplayUnit, CWallet::minTxFee.GetFeePerK()));
 
-    QString toolTip3 = tr("This label turns red, if any recipient receives an amount smaller than %1.").arg(BitcoinUnits::formatWithUnit(nDisplayUnit, CTransaction::minRelayTxFee.GetFee(546)));
+    QString toolTip3 = tr("This label turns red, if any recipient receives an amount smaller than %1.").arg(BitcoinUnits::formatWithUnit(nDisplayUnit, ::minRelayTxFee.GetFee(546)));
 
     // how many satoshis the estimated fee can vary per byte we guess wrong
-    double dFeeVary = (double)std::max(CTransaction::minTxFee.GetFeePerK(), payTxFee.GetFeePerK()) / 1000;
+    double dFeeVary = (double)std::max(CWallet::minTxFee.GetFeePerK(), payTxFee.GetFeePerK()) / 1000;
     QString toolTip4 = tr("Can vary +/- %1 satoshi(s) per input.").arg(dFeeVary);
 
     l3->setToolTip(toolTip4);
@@ -732,7 +740,7 @@ void CoinControlDialog::updateView()
 
             // priority
             double dPriority = ((double)out.tx->vout[out.i].nValue  / (nInputSize + 78)) * (out.nDepth+1); // 78 = 2 * 34 + 10
-            itemOutput->setText(COLUMN_PRIORITY, CoinControlDialog::getPriorityLabel(dPriority));
+            itemOutput->setText(COLUMN_PRIORITY, CoinControlDialog::getPriorityLabel(mempool, dPriority));
             itemOutput->setText(COLUMN_PRIORITY_INT64, strPad(QString::number((int64_t)dPriority), 20, " "));
             dPrioritySum += (double)out.tx->vout[out.i].nValue  * (out.nDepth+1);
             nInputSum    += nInputSize;
@@ -765,7 +773,7 @@ void CoinControlDialog::updateView()
             itemWalletAddress->setText(COLUMN_CHECKBOX, "(" + QString::number(nChildren) + ")");
             itemWalletAddress->setText(COLUMN_AMOUNT, BitcoinUnits::format(nDisplayUnit, nSum));
             itemWalletAddress->setText(COLUMN_AMOUNT_INT64, strPad(QString::number(nSum), 15, " "));
-            itemWalletAddress->setText(COLUMN_PRIORITY, CoinControlDialog::getPriorityLabel(dPrioritySum));
+            itemWalletAddress->setText(COLUMN_PRIORITY, CoinControlDialog::getPriorityLabel(mempool, dPrioritySum));
             itemWalletAddress->setText(COLUMN_PRIORITY_INT64, strPad(QString::number((int64_t)dPrioritySum), 20, " "));
         }
     }
diff --git a/src/qt/coincontroldialog.h b/src/qt/coincontroldialog.h
index 465e2a009d..4f7422642f 100644
--- a/src/qt/coincontroldialog.h
+++ b/src/qt/coincontroldialog.h
@@ -19,6 +19,7 @@ namespace Ui {
 }
 class WalletModel;
 class CCoinControl;
+class CTxMemPool;
 
 class CoinControlDialog : public QDialog
 {
@@ -32,7 +33,7 @@ public:
 
     // static because also called from sendcoinsdialog
     static void updateLabels(WalletModel*, QDialog*);
-    static QString getPriorityLabel(double);
+    static QString getPriorityLabel(const CTxMemPool& pool, double);
 
     static QList<qint64> payAmounts;
     static CCoinControl *coinControl;
diff --git a/src/qt/guiutil.cpp b/src/qt/guiutil.cpp
index 81b9054252..60a131df7e 100644
--- a/src/qt/guiutil.cpp
+++ b/src/qt/guiutil.cpp
@@ -11,6 +11,7 @@
 
 #include "core.h"
 #include "init.h"
+#include "main.h"
 #include "protocol.h"
 #include "util.h"
 
@@ -212,7 +213,7 @@ bool isDust(const QString& address, qint64 amount)
     CTxDestination dest = CBitcoinAddress(address.toStdString()).Get();
     CScript script; script.SetDestination(dest);
     CTxOut txOut(amount, script);
-    return txOut.IsDust(CTransaction::minRelayTxFee);
+    return txOut.IsDust(::minRelayTxFee);
 }
 
 QString HtmlEscape(const QString& str, bool fMultiLine)
diff --git a/src/qt/optionsdialog.cpp b/src/qt/optionsdialog.cpp
index 12d54dff64..9502dba904 100644
--- a/src/qt/optionsdialog.cpp
+++ b/src/qt/optionsdialog.cpp
@@ -14,7 +14,10 @@
 #include "monitoreddatamapper.h"
 #include "optionsmodel.h"
 
-#include "main.h" // for CTransaction::minTxFee and MAX_SCRIPTCHECK_THREADS
+#include "main.h" // for MAX_SCRIPTCHECK_THREADS
+#ifdef ENABLE_WALLET
+#include "wallet.h" // for CWallet::minTxFee
+#endif
 #include "netbase.h"
 #include "txdb.h" // for -dbcache defaults
 
@@ -101,7 +104,9 @@ OptionsDialog::OptionsDialog(QWidget *parent) :
 #endif
 
     ui->unit->setModel(new BitcoinUnits(this));
-    ui->transactionFee->setSingleStep(CTransaction::minTxFee.GetFeePerK());
+#ifdef ENABLE_WALLET
+    ui->transactionFee->setSingleStep(CWallet::minTxFee.GetFeePerK());
+#endif
 
     /* Widget-to-option mapper */
     mapper = new MonitoredDataMapper(this);
diff --git a/src/qt/paymentserver.cpp b/src/qt/paymentserver.cpp
index 6ca90f0513..53db2c5cd9 100644
--- a/src/qt/paymentserver.cpp
+++ b/src/qt/paymentserver.cpp
@@ -551,7 +551,7 @@ bool PaymentServer::processPaymentRequest(PaymentRequestPlus& request, SendCoins
 
         // Extract and check amounts
         CTxOut txOut(sendingTo.second, sendingTo.first);
-        if (txOut.IsDust(CTransaction::minRelayTxFee)) {
+        if (txOut.IsDust(::minRelayTxFee)) {
             emit message(tr("Payment request error"), tr("Requested payment amount of %1 is too small (considered dust).")
                 .arg(BitcoinUnits::formatWithUnit(optionsModel->getDisplayUnit(), sendingTo.second)),
                 CClientUIInterface::MSG_ERROR);
diff --git a/src/rpcmisc.cpp b/src/rpcmisc.cpp
index 5b470516a1..9ed6b52513 100644
--- a/src/rpcmisc.cpp
+++ b/src/rpcmisc.cpp
@@ -84,7 +84,7 @@ Value getinfo(const Array& params, bool fHelp)
         obj.push_back(Pair("unlocked_until", nWalletUnlockTime));
     obj.push_back(Pair("paytxfee",      ValueFromAmount(payTxFee.GetFeePerK())));
 #endif
-    obj.push_back(Pair("relayfee",      ValueFromAmount(CTransaction::minRelayTxFee.GetFeePerK())));
+    obj.push_back(Pair("relayfee",      ValueFromAmount(::minRelayTxFee.GetFeePerK())));
     obj.push_back(Pair("errors",        GetWarnings("statusbar")));
     return obj;
 }
diff --git a/src/rpcnet.cpp b/src/rpcnet.cpp
index 2d7abb2d58..cd3bd59f8f 100644
--- a/src/rpcnet.cpp
+++ b/src/rpcnet.cpp
@@ -372,7 +372,7 @@ Value getnetworkinfo(const Array& params, bool fHelp)
     obj.push_back(Pair("timeoffset",    GetTimeOffset()));
     obj.push_back(Pair("connections",   (int)vNodes.size()));
     obj.push_back(Pair("proxy",         (proxy.first.IsValid() ? proxy.first.ToStringIPPort() : string())));
-    obj.push_back(Pair("relayfee",      ValueFromAmount(CTransaction::minRelayTxFee.GetFeePerK())));
+    obj.push_back(Pair("relayfee",      ValueFromAmount(::minRelayTxFee.GetFeePerK())));
     Array localAddresses;
     {
         LOCK(cs_mapLocalHost);
diff --git a/src/txmempool.cpp b/src/txmempool.cpp
index 97a426dd35..a852de5da8 100644
--- a/src/txmempool.cpp
+++ b/src/txmempool.cpp
@@ -80,13 +80,13 @@ public:
 
     // Used as belt-and-suspenders check when reading to detect
     // file corruption
-    bool AreSane(const std::vector<CFeeRate>& vecFee)
+    bool AreSane(const std::vector<CFeeRate>& vecFee, const CFeeRate& minRelayFee)
     {
         BOOST_FOREACH(CFeeRate fee, vecFee)
         {
             if (fee < CFeeRate(0))
                 return false;
-            if (fee.GetFee(1000) > CTransaction::minRelayTxFee.GetFee(1000) * 10000)
+            if (fee.GetFeePerK() > minRelayFee.GetFeePerK() * 10000)
                 return false;
         }
         return true;
@@ -109,10 +109,10 @@ public:
         fileout << vecPriority;
     }
 
-    void Read(CAutoFile& filein) {
+    void Read(CAutoFile& filein, const CFeeRate& minRelayFee) {
         std::vector<CFeeRate> vecFee;
         filein >> vecFee;
-        if (AreSane(vecFee))
+        if (AreSane(vecFee, minRelayFee))
             feeSamples.insert(feeSamples.end(), vecFee.begin(), vecFee.end());
         else
             throw runtime_error("Corrupt fee value in estimates file.");
@@ -141,7 +141,7 @@ private:
 
     // nBlocksAgo is 0 based, i.e. transactions that confirmed in the highest seen block are
     // nBlocksAgo == 0, transactions in the block before that are nBlocksAgo == 1 etc.
-    void seenTxConfirm(CFeeRate feeRate, double dPriority, int nBlocksAgo)
+    void seenTxConfirm(const CFeeRate& feeRate, const CFeeRate& minRelayFee, double dPriority, int nBlocksAgo)
     {
         // Last entry records "everything else".
         int nBlocksTruncated = min(nBlocksAgo, (int) history.size() - 1);
@@ -149,7 +149,7 @@ private:
 
         // We need to guess why the transaction was included in a block-- either
         // because it is high-priority or because it has sufficient fees.
-        bool sufficientFee = (feeRate > CTransaction::minRelayTxFee);
+        bool sufficientFee = (feeRate > minRelayFee);
         bool sufficientPriority = AllowFree(dPriority);
         const char* assignedTo = "unassigned";
         if (sufficientFee && !sufficientPriority)
@@ -177,7 +177,7 @@ public:
         history.resize(nEntries);
     }
 
-    void seenBlock(const std::vector<CTxMemPoolEntry>& entries, int nBlockHeight)
+    void seenBlock(const std::vector<CTxMemPoolEntry>& entries, int nBlockHeight, const CFeeRate minRelayFee)
     {
         if (nBlockHeight <= nBestSeenHeight)
         {
@@ -222,7 +222,7 @@ public:
                 // Fees are stored and reported as BTC-per-kb:
                 CFeeRate feeRate(entry->GetFee(), entry->GetTxSize());
                 double dPriority = entry->GetPriority(entry->GetHeight()); // Want priority when it went IN
-                seenTxConfirm(feeRate, dPriority, i);
+                seenTxConfirm(feeRate, minRelayFee, dPriority, i);
             }
         }
         for (size_t i = 0; i < history.size(); i++) {
@@ -251,8 +251,13 @@ public:
             std::sort(sortedFeeSamples.begin(), sortedFeeSamples.end(),
                       std::greater<CFeeRate>());
         }
-        if (sortedFeeSamples.size() == 0)
+        if (sortedFeeSamples.size() < 11)
+        {
+            // Eleven is Gavin's Favorite Number
+            // ... but we also take a maximum of 10 samples per block so eleven means
+            // we're getting samples from at least two different blocks
             return CFeeRate(0);
+        }
 
         int nBucketSize = history.at(nBlocksToConfirm).FeeSamples();
 
@@ -281,7 +286,7 @@ public:
             std::sort(sortedPrioritySamples.begin(), sortedPrioritySamples.end(),
                       std::greater<double>());
         }
-        if (sortedPrioritySamples.size() == 0)
+        if (sortedPrioritySamples.size() < 11)
             return -1.0;
 
         int nBucketSize = history.at(nBlocksToConfirm).PrioritySamples();
@@ -308,7 +313,7 @@ public:
         }
     }
 
-    void Read(CAutoFile& filein)
+    void Read(CAutoFile& filein, const CFeeRate& minRelayFee)
     {
         filein >> nBestSeenHeight;
         size_t numEntries;
@@ -317,14 +322,14 @@ public:
         for (size_t i = 0; i < numEntries; i++)
         {
             CBlockAverage entry;
-            entry.Read(filein);
+            entry.Read(filein, minRelayFee);
             history.push_back(entry);
         }
     }
 };
 
 
-CTxMemPool::CTxMemPool()
+CTxMemPool::CTxMemPool(const CFeeRate& _minRelayFee) : minRelayFee(_minRelayFee)
 {
     // Sanity checks off by default for performance, because otherwise
     // accepting transactions becomes O(N^2) where N is the number
@@ -440,7 +445,7 @@ void CTxMemPool::removeForBlock(const std::vector<CTransaction>& vtx, unsigned i
         if (mapTx.count(hash))
             entries.push_back(mapTx[hash]);
     }
-    minerPolicyEstimator->seenBlock(entries, nBlockHeight);
+    minerPolicyEstimator->seenBlock(entries, nBlockHeight, minRelayFee);
     BOOST_FOREACH(const CTransaction& tx, vtx)
     {
         std::list<CTransaction> dummy;
@@ -555,7 +560,7 @@ CTxMemPool::ReadFeeEstimates(CAutoFile& filein)
             return error("CTxMemPool::ReadFeeEstimates() : up-version (%d) fee estimate file", nVersionRequired);
 
         LOCK(cs);
-        minerPolicyEstimator->Read(filein);
+        minerPolicyEstimator->Read(filein, minRelayFee);
     }
     catch (std::exception &e) {
         LogPrintf("CTxMemPool::ReadFeeEstimates() : unable to read policy estimator data (non-fatal)");
diff --git a/src/txmempool.h b/src/txmempool.h
index f7dbb126a0..41b2c52f39 100644
--- a/src/txmempool.h
+++ b/src/txmempool.h
@@ -67,13 +67,15 @@ private:
     unsigned int nTransactionsUpdated;
     CMinerPolicyEstimator* minerPolicyEstimator;
 
+    CFeeRate minRelayFee; // Passed to constructor to avoid dependency on main
+
 public:
     mutable CCriticalSection cs;
     std::map<uint256, CTxMemPoolEntry> mapTx;
     std::map<COutPoint, CInPoint> mapNextTx;
     std::map<uint256, std::pair<double, int64_t> > mapDeltas;
 
-    CTxMemPool();
+    CTxMemPool(const CFeeRate& _minRelayFee);
     ~CTxMemPool();
 
     /*
diff --git a/src/wallet.cpp b/src/wallet.cpp
index daca7ac04b..318a1388d2 100644
--- a/src/wallet.cpp
+++ b/src/wallet.cpp
@@ -18,8 +18,12 @@ using namespace std;
 
 // Settings
 CFeeRate payTxFee(DEFAULT_TRANSACTION_FEE);
+unsigned int nTxConfirmTarget = 1;
 bool bSpendZeroConfChange = true;
 
+/** Fees smaller than this (in satoshi) are considered zero fee (for transaction creation) */
+CFeeRate CWallet::minTxFee = CFeeRate(10000);  // Override with -mintxfee
+
 //////////////////////////////////////////////////////////////////////////////
 //
 // mapWallet
@@ -1273,6 +1277,7 @@ bool CWallet::CreateTransaction(const vector<pair<CScript, int64_t> >& vecSend,
         return false;
     }
 
+    wtxNew.fTimeReceivedIsTxTime = true;
     wtxNew.BindWallet(this);
     CMutableTransaction txNew;
 
@@ -1292,7 +1297,7 @@ bool CWallet::CreateTransaction(const vector<pair<CScript, int64_t> >& vecSend,
                 BOOST_FOREACH (const PAIRTYPE(CScript, int64_t)& s, vecSend)
                 {
                     CTxOut txout(s.second, s.first);
-                    if (txout.IsDust(CTransaction::minRelayTxFee))
+                    if (txout.IsDust(::minRelayTxFee))
                     {
                         strFailReason = _("Transaction amount too small");
                         return false;
@@ -1353,7 +1358,7 @@ bool CWallet::CreateTransaction(const vector<pair<CScript, int64_t> >& vecSend,
 
                     // Never create dust outputs; if we would, just
                     // add the dust to the fee.
-                    if (newTxOut.IsDust(CTransaction::minRelayTxFee))
+                    if (newTxOut.IsDust(::minRelayTxFee))
                     {
                         nFeeRet += nChange;
                         reservekey.ReturnKey();
@@ -1393,19 +1398,31 @@ bool CWallet::CreateTransaction(const vector<pair<CScript, int64_t> >& vecSend,
                 }
                 dPriority = wtxNew.ComputePriority(dPriority, nBytes);
 
-                // Check that enough fee is included
-                int64_t nPayFee = payTxFee.GetFee(nBytes);
-                bool fAllowFree = AllowFree(dPriority);
-                int64_t nMinFee = GetMinFee(wtxNew, nBytes, fAllowFree, GMF_SEND);
-                if (nFeeRet < max(nPayFee, nMinFee))
+                int64_t nFeeNeeded = GetMinimumFee(nBytes, nTxConfirmTarget, mempool);
+
+                if (nFeeRet >= nFeeNeeded)
+                    break; // Done, enough fee included.
+
+                // Too big to send for free? Include more fee and try again:
+                if (nBytes > MAX_FREE_TRANSACTION_CREATE_SIZE)
                 {
-                    nFeeRet = max(nPayFee, nMinFee);
+                    nFeeRet = nFeeNeeded;
                     continue;
                 }
 
-                wtxNew.fTimeReceivedIsTxTime = true;
+                // Not enough fee: enough priority?
+                double dPriorityNeeded = mempool.estimatePriority(nTxConfirmTarget);
+                // Not enough mempool history to estimate: use hard-coded AllowFree.
+                if (dPriorityNeeded <= 0 && AllowFree(dPriority))
+                    break;
+
+                // Small enough, and priority high enough, to send for free
+                if (dPriority >= dPriorityNeeded)
+                    break;
 
-                break;
+                // Include more fee and try again.
+                nFeeRet = nFeeNeeded;
+                continue;
             }
         }
     }
@@ -1513,6 +1530,20 @@ string CWallet::SendMoneyToDestination(const CTxDestination& address, int64_t nV
     return SendMoney(scriptPubKey, nValue, wtxNew);
 }
 
+int64_t CWallet::GetMinimumFee(unsigned int nTxBytes, unsigned int nConfirmTarget, const CTxMemPool& pool)
+{
+    // payTxFee is user-set "I want to pay this much"
+    int64_t nFeeNeeded = payTxFee.GetFee(nTxBytes);
+    // User didn't set: use -txconfirmtarget to estimate...
+    if (nFeeNeeded == 0)
+        nFeeNeeded = pool.estimateFee(nConfirmTarget).GetFee(nTxBytes);
+    // ... unless we don't have enough mempool data, in which case fall
+    // back to a hard-coded fee
+    if (nFeeNeeded == 0)
+        nFeeNeeded = minTxFee.GetFee(nTxBytes);
+    return nFeeNeeded;
+}
+
 
 
 
diff --git a/src/wallet.h b/src/wallet.h
index 1c2512d678..a5162bb838 100644
--- a/src/wallet.h
+++ b/src/wallet.h
@@ -25,12 +25,15 @@
 
 // Settings
 extern CFeeRate payTxFee;
+extern unsigned int nTxConfirmTarget;
 extern bool bSpendZeroConfChange;
 
 // -paytxfee default
 static const int64_t DEFAULT_TRANSACTION_FEE = 0;
 // -paytxfee will warn if called with a higher fee than this amount (in satoshis) per KB
 static const int nHighTransactionFeeWarning = 0.01 * COIN;
+// Largest (in bytes) free transaction we're willing to create
+static const unsigned int MAX_FREE_TRANSACTION_CREATE_SIZE = 1000;
 
 class CAccountingEntry;
 class CCoinControl;
@@ -265,6 +268,9 @@ public:
     std::string SendMoney(CScript scriptPubKey, int64_t nValue, CWalletTx& wtxNew);
     std::string SendMoneyToDestination(const CTxDestination &address, int64_t nValue, CWalletTx& wtxNew);
 
+    static CFeeRate minTxFee;
+    static int64_t GetMinimumFee(unsigned int nTxBytes, unsigned int nConfirmTarget, const CTxMemPool& pool);
+
     bool NewKeyPool();
     bool TopUpKeyPool(unsigned int kpSize = 0);
     void ReserveKeyFromKeyPool(int64_t& nIndex, CKeyPool& keypool);