From e868b22917aee4c888f843bd86a2bf8ea29530eb Mon Sep 17 00:00:00 2001
From: Suhas Daftuar <sdaftuar@gmail.com>
Date: Fri, 19 Jan 2018 10:38:58 -0500
Subject: [PATCH] fee estimator: avoid sorting mempool on shutdown

---
 src/init.cpp        |  2 +-
 src/policy/fees.cpp | 13 +++++++------
 src/policy/fees.h   |  2 +-
 3 files changed, 9 insertions(+), 8 deletions(-)

diff --git a/src/init.cpp b/src/init.cpp
index b48802637b..564b2b3328 100644
--- a/src/init.cpp
+++ b/src/init.cpp
@@ -205,7 +205,7 @@ void Shutdown()
 
     if (fFeeEstimatesInitialized)
     {
-        ::feeEstimator.FlushUnconfirmed(::mempool);
+        ::feeEstimator.FlushUnconfirmed();
         fs::path est_path = GetDataDir() / FEE_ESTIMATES_FILENAME;
         CAutoFile est_fileout(fsbridge::fopen(est_path, "wb"), SER_DISK, CLIENT_VERSION);
         if (!est_fileout.IsNull())
diff --git a/src/policy/fees.cpp b/src/policy/fees.cpp
index 9142f3706d..79b450e3e6 100644
--- a/src/policy/fees.cpp
+++ b/src/policy/fees.cpp
@@ -981,16 +981,17 @@ bool CBlockPolicyEstimator::Read(CAutoFile& filein)
     return true;
 }
 
-void CBlockPolicyEstimator::FlushUnconfirmed(CTxMemPool& pool) {
+void CBlockPolicyEstimator::FlushUnconfirmed() {
     int64_t startclear = GetTimeMicros();
-    std::vector<uint256> txids;
-    pool.queryHashes(txids);
     LOCK(cs_feeEstimator);
-    for (auto& txid : txids) {
-        removeTx(txid, false);
+    size_t num_entries = mapMemPoolTxs.size();
+    // Remove every entry in mapMemPoolTxs
+    while (!mapMemPoolTxs.empty()) {
+        auto mi = mapMemPoolTxs.begin();
+        removeTx(mi->first, false); // this calls erase() on mapMemPoolTxs
     }
     int64_t endclear = GetTimeMicros();
-    LogPrint(BCLog::ESTIMATEFEE, "Recorded %u unconfirmed txs from mempool in %gs\n",txids.size(), (endclear - startclear)*0.000001);
+    LogPrint(BCLog::ESTIMATEFEE, "Recorded %u unconfirmed txs from mempool in %gs\n", num_entries, (endclear - startclear)*0.000001);
 }
 
 FeeFilterRounder::FeeFilterRounder(const CFeeRate& minIncrementalFee)
diff --git a/src/policy/fees.h b/src/policy/fees.h
index 96a842b7a1..5f69e989c1 100644
--- a/src/policy/fees.h
+++ b/src/policy/fees.h
@@ -223,7 +223,7 @@ public:
     bool Read(CAutoFile& filein);
 
     /** Empty mempool transactions on shutdown to record failure to confirm for txs still in mempool */
-    void FlushUnconfirmed(CTxMemPool& pool);
+    void FlushUnconfirmed();
 
     /** Calculation of highest target that estimates are tracked for */
     unsigned int HighestTargetTracked(FeeEstimateHorizon horizon) const;