Merge remote-tracking branch 'origin/topic/timw/sessions-unordered-map'

* origin/topic/timw/sessions-unordered-map:
  Only sort sessions during Drain() if a random seed is set
  Use unordered_map to store sessions for performance reasons

CHANGES

@@ -1,3 +1,8 @@
+4.2.0-dev.68 | 2021-08-04 09:57:32 +0100
+
+  * Use unordered_map to store sessions for performance reasons. This might lead to an 8-9% speedup of Zeek.
+    See GH-1706 for details. (Tim Wojtulewicz, Corelight)
+
 4.2.0-dev.64 | 2021-08-03 10:23:41 +0100
 
   * Under certain circumstances, Zeek processes could get into an infinite looping state inside RotationTimer.

VERSION

@@ -1 +1 @@
-4.2.0-dev.64
+4.2.0-dev.68

src/session/Key.cc

@@ -70,4 +70,14 @@ bool Key::operator<(const Key& rhs) const
 	return memcmp(data, rhs.data, size) < 0;
 	}
 
+bool Key::operator==(const Key& rhs) const
+	{
+	if ( size != rhs.size )
+		return false;
+	else if ( type != rhs.type )
+		return false;
+
+	return memcmp(data, rhs.data, size) == 0;
+	}
+
 } // namespace zeek::session::detail

src/session/Key.h

@@ -4,9 +4,12 @@
 
 #include <cstddef>
 #include <cstdint>
+#include "zeek/Hash.h"
 
 namespace zeek::session::detail {
 
+struct KeyHash;
+
 /**
  * This type is used as the key for the map in SessionManager. It represents a
  * raw block of memory that points to a key of some type for a session, such as
@@ -57,12 +60,23 @@ public:
 	void CopyData();
 
 	bool operator<(const Key& rhs) const;
+	bool operator==(const Key& rhs) const;
+
+	std::size_t Hash() const {
+		return zeek::detail::HashKey::HashBytes(data, size);
+	}
 
 private:
+	friend struct KeyHash;
+
 	const uint8_t* data = nullptr;
 	size_t size = 0;
 	size_t type = CONNECTION_KEY_TYPE;
 	bool copied = false;
 };
 
+struct KeyHash {
+	std::size_t operator()(const Key& k) const { return k.Hash(); }
+};
+
 } // namespace zeek::session::detail

src/session/Manager.cc

@@ -218,11 +218,34 @@ void Manager::Insert(Session* s, bool remove_existing)
 
 void Manager::Drain()
 	{
-	for ( const auto& entry : session_map )
+	// If a random seed was passed in, we're most likely in testing mode and need the
+	// order of the sessions to be consistent. Sort the keys to force that order
+	// every run.
+	if ( zeek::util::detail::have_random_seed() )
 		{
-		Session* tc = entry.second;
+		std::vector<const detail::Key*> keys;
-		tc->Done();
+		keys.reserve(session_map.size());
-		tc->RemovalEvent();
+
+		for ( auto& entry : session_map )
+			keys.push_back(&(entry.first));
+		std::sort(keys.begin(), keys.end(), [](const detail::Key* a, const detail::Key* b) {
+			                                    return *a < *b; });
+
+		for ( const auto* k : keys )
+			{
+			Session* tc = session_map.at(*k);
+			tc->Done();
+			tc->RemovalEvent();
+			}
+		}
+	else
+		{
+		for ( const auto& entry : session_map )
+			{
+			Session* tc = entry.second;
+			tc->Done();
+			tc->RemovalEvent();
+			}
 		}
 	}
 

src/session/Manager.h

@@ -3,7 +3,7 @@
 #pragma once
 
 #include <sys/types.h> // for u_char
-#include <map>
+#include <unordered_map>
 #include <utility>
 
 #include "zeek/Frag.h"
@@ -119,7 +119,7 @@ public:
 
 private:
 
-	using SessionMap = std::map<detail::Key, Session*>;
+	using SessionMap = std::unordered_map<detail::Key, Session*, detail::KeyHash>;
 
 	// Inserts a new connection into the sessions map. If a connection with
 	// the same key already exists in the map, it will be overwritten by