Merge bitcoin/bitcoin#18722: addrman: improve performance by using more suitable containers

a92485b2c250fd18f55d22aa32722bf52ab32bfe addrman: use unordered_map instead of map (Vasil Dimov)

Pull request description:

  `CAddrMan` uses `std::map` internally even though it does not require
  that the map's elements are sorted. `std::map`'s access time is
  `O(log(map size))`. `std::unordered_map` is more suitable as it has a
  `O(1)` access time.

  This patch lowers the execution times of `CAddrMan`'s methods as follows
  (as per `src/bench/addrman.cpp`):

  ```
  AddrMan::Add(): -3.5%
  AddrMan::GetAddr(): -76%
  AddrMan::Good(): -0.38%
  AddrMan::Select(): -45%
  ```

ACKs for top commit:
  jonatack:
    ACK a92485b2c250fd18f55d22aa32722bf52ab32bfe
  achow101:
    ACK a92485b2c250fd18f55d22aa32722bf52ab32bfe
  hebasto:
    re-ACK a92485b2c250fd18f55d22aa32722bf52ab32bfe, only suggested changes and rebased since my [previous](https://github.com/bitcoin/bitcoin/pull/18722#pullrequestreview-666663681) review.

Tree-SHA512: d82959a00e6bd68a6c4c5a265dd08849e6602ac3231293b7a3a3b7bf82ab1d3ba77f8ca682919c15c5d601b13e468b8836fcf19595248116635f7a50d02ed603

src/addrman.cpp

@@ -13,6 +13,8 @@
 
 #include <cmath>
 #include <optional>
+#include <unordered_map>
+#include <unordered_set>
 
 int CAddrInfo::GetTriedBucket(const uint256& nKey, const std::vector<bool> &asmap) const
 {
@@ -115,12 +117,12 @@ CAddrInfo* CAddrMan::Find(const CService& addr, int* pnId)
         addr2.SetPort(0);
     }
 
-    std::map<CService, int>::iterator it = mapAddr.find(addr2);
+    const auto it = mapAddr.find(addr2);
     if (it == mapAddr.end())
         return nullptr;
     if (pnId)
         *pnId = (*it).second;
-    std::map<int, CAddrInfo>::iterator it2 = mapInfo.find((*it).second);
+    const auto it2 = mapInfo.find((*it).second);
     if (it2 != mapInfo.end())
         return &(*it2).second;
     return nullptr;
@@ -482,8 +484,8 @@ CAddrInfo CAddrMan::Select_(bool newOnly) const
 int CAddrMan::Check_()
 {
     AssertLockHeld(cs);
-    std::set<int> setTried;
-    std::map<int, int> mapNew;
+    std::unordered_set<int> setTried;
+    std::unordered_map<int, int> mapNew;
 
     if (vRandom.size() != (size_t)(nTried + nNew))
         return -7;

src/addrman.h

@@ -8,22 +8,22 @@
 
 #include <clientversion.h>
 #include <config/bitcoin-config.h>
+#include <fs.h>
+#include <hash.h>
 #include <netaddress.h>
 #include <protocol.h>
 #include <random.h>
+#include <streams.h>
 #include <sync.h>
 #include <timedata.h>
 #include <tinyformat.h>
 #include <util/system.h>
 
-#include <fs.h>
-#include <hash.h>
 #include <ios>
-#include <map>
 #include <optional>
 #include <set>
 #include <stdint.h>
-#include <streams.h>
+#include <unordered_map>
 #include <vector>
 
 /**
@@ -257,7 +257,7 @@ public:
 
         int nUBuckets = ADDRMAN_NEW_BUCKET_COUNT ^ (1 << 30);
         s << nUBuckets;
-        std::map<int, int> mapUnkIds;
+        std::unordered_map<int, int> mapUnkIds;
         int nIds = 0;
         for (const auto& entry : mapInfo) {
             mapUnkIds[entry.first] = nIds;
@@ -448,13 +448,13 @@ public:
 
         // Prune new entries with refcount 0 (as a result of collisions).
         int nLostUnk = 0;
-        for (std::map<int, CAddrInfo>::const_iterator it = mapInfo.begin(); it != mapInfo.end(); ) {
+        for (auto it = mapInfo.cbegin(); it != mapInfo.cend(); ) {
             if (it->second.fInTried == false && it->second.nRefCount == 0) {
-                std::map<int, CAddrInfo>::const_iterator itCopy = it++;
+                const auto itCopy = it++;
                 Delete(itCopy->first);
-                nLostUnk++;
+                ++nLostUnk;
             } else {
-                it++;
+                ++it;
             }
         }
         if (nLost + nLostUnk > 0) {
@@ -682,10 +682,10 @@ private:
     int nIdCount GUARDED_BY(cs);
 
     //! table with information about all nIds
-    std::map<int, CAddrInfo> mapInfo GUARDED_BY(cs);
+    std::unordered_map<int, CAddrInfo> mapInfo GUARDED_BY(cs);
 
     //! find an nId based on its network address
-    std::map<CService, int> mapAddr GUARDED_BY(cs);
+    std::unordered_map<CNetAddr, int, CNetAddrHash> mapAddr GUARDED_BY(cs);
 
     //! randomly-ordered vector of all nIds
     //! This is mutable because it is unobservable outside the class, so any

src/netaddress.h

@@ -11,7 +11,9 @@
 
 #include <attributes.h>
 #include <compat.h>
+#include <crypto/siphash.h>
 #include <prevector.h>
+#include <random.h>
 #include <serialize.h>
 #include <tinyformat.h>
 #include <util/strencodings.h>
@@ -251,6 +253,7 @@ public:
         }
     }
 
+    friend class CNetAddrHash;
     friend class CSubNet;
 
 private:
@@ -465,6 +468,22 @@ public:
     }
 };
 
+class CNetAddrHash
+{
+public:
+    size_t operator()(const CNetAddr& a) const noexcept
+    {
+        CSipHasher hasher(m_salt_k0, m_salt_k1);
+        hasher.Write(a.m_net);
+        hasher.Write(a.m_addr.data(), a.m_addr.size());
+        return static_cast<size_t>(hasher.Finalize());
+    }
+
+private:
+    const uint64_t m_salt_k0 = GetRand(std::numeric_limits<uint64_t>::max());
+    const uint64_t m_salt_k1 = GetRand(std::numeric_limits<uint64_t>::max());
+};
+
 class CSubNet
 {
 protected: