Implement accurate memory accounting for mempool

src/txmempool.h

@@ -40,6 +40,7 @@ private:
     CAmount nFee; //! Cached to avoid expensive parent-transaction lookups
     size_t nTxSize; //! ... and avoid recomputing tx size
     size_t nModSize; //! ... and modified size for priority
+    size_t nUsageSize; //! ... and total memory usage
     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
@@ -58,6 +59,7 @@ public:
     int64_t GetTime() const { return nTime; }
     unsigned int GetHeight() const { return nHeight; }
     bool WasClearAtEntry() const { return hadNoDependencies; }
+    size_t DynamicMemoryUsage() const { return nUsageSize; }
 };
 
 class CBlockPolicyEstimator;
@@ -73,6 +75,7 @@ public:
     CInPoint(const CTransaction* ptxIn, uint32_t nIn) { ptx = ptxIn; n = nIn; }
     void SetNull() { ptx = NULL; n = (uint32_t) -1; }
     bool IsNull() const { return (ptx == NULL && n == (uint32_t) -1); }
+    size_t DynamicMemoryUsage() const { return 0; }
 };
 
 /**
@@ -93,6 +96,7 @@ private:
     CBlockPolicyEstimator* minerPolicyEstimator;
 
     uint64_t totalTxSize = 0; //! sum of all mempool tx' byte sizes
+    uint64_t cachedInnerUsage; //! sum of dynamic memory usage of all the map elements (NOT the maps themselves)
 
 public:
     mutable CCriticalSection cs;
@@ -141,6 +145,7 @@ public:
         LOCK(cs);
         return mapTx.size();
     }
+
     uint64_t GetTotalTxSize()
     {
         LOCK(cs);
@@ -164,6 +169,8 @@ public:
     /** Write/Read estimates to disk */
     bool WriteFeeEstimates(CAutoFile& fileout) const;
     bool ReadFeeEstimates(CAutoFile& filein);
+
+    size_t DynamicMemoryUsage() const;
 };
 
 /**