simplify connection attempt distribution logic to not lower the connection rate with a downloading torrent among seeding ones

include/libtorrent/torrent.hpp

@@ -433,7 +433,6 @@ namespace libtorrent
 
 		bool want_more_peers() const;
 		bool try_connect_peer();
-		void give_connect_points(int points);
 		void add_peer(tcp::endpoint const& adr, int source);
 
 		// the number of peers that belong to this torrent
@@ -1221,19 +1220,9 @@ namespace libtorrent
 		// the maximum number of uploads for this torrent
 		unsigned int m_max_uploads:24;
 
-		// this is the deficit counter in the Deficit Round Robin
+		// these are the flags sent in on a call to save_resume_data
-		// used to determine which torrent gets the next
+		// we need to save them to check them in write_resume_data
-		// connection attempt. See:
+		boost::uint8_t m_save_resume_flags;
-		// http://www.ecs.umass.edu/ece/wolf/courses/ECE697J/papers/DRR.pdf
-		// The quanta assigned to each torrent depends on the torrents
-		// priority, whether it's a seed and the number of connected
-		// peers it has. This has the effect that some torrents
-		// will have more connection attempts than other. Each
-		// connection attempt costs 100 points from the deficit
-		// counter. points are deducted in try_connect_peer and
-		// increased in give_connect_points. Outside of the
-		// torrent object, these points are called connect_points.
-		boost::uint8_t m_deficit_counter;
 
 		// the number of unchoked peers in this torrent
 		unsigned int m_num_uploads:24;
@@ -1334,10 +1323,6 @@ namespace libtorrent
 		// round-robin index into m_interfaces
 		mutable boost::uint8_t m_interface_index;
 
-		// these are the flags sent in on a call to save_resume_data
-		// we need to save them to check them in write_resume_data
-		boost::uint8_t m_save_resume_flags;
-
 		// set to true when this torrent has been paused but
 		// is waiting to finish all current download requests
 		// before actually closing all connections

src/session_impl.cpp

@@ -3399,43 +3399,42 @@ namespace aux {
 				torrent& t = *m_next_connect_torrent->second;
 				if (t.want_more_peers())
 				{
-					// 133 is so that the average of downloaders with
+					// have a bias to give more connection attempts
-					// more than average peers and less than average
+					// to downloading torrents than seed, and even
-					// peers will end up being 100 (i.e. 133 / 2 = 66)
+					// more to downloading torrents with less than
-					int connect_points = 133;
+					// average number of connections
-					// have a bias against torrents with more peers
+					int num_attempts = 1;
-					// than average
+					if (!t.is_seed())
-					if (!t.is_seed() && t.num_peers() > average_peers)
-						connect_points /= 2;
-					// if this is a seed and there is a torrent that
-					// is downloading, lower the rate at which this
-					// torrent gets connections.
-					// dividing by num_seeds will have the effect
-					// that all seed will get as many connections
-					// together, as a single downloading torrent.
-					if (t.is_seed() && num_downloads > 0)
-						connect_points /= num_seeds + 1;
-					if (connect_points <= 0) connect_points = 1;
-					t.give_connect_points(connect_points);
-					TORRENT_TRY
 					{
-						if (t.try_connect_peer())
+						++num_attempts;
-						{
+						if (t.num_peers() < average_peers)
-							--max_connections;
+							++num_attempts;
-							--free_slots;
-							steps_since_last_connect = 0;
-#ifdef TORRENT_STATS
-							++m_connection_attempts;
-#endif
-						}
 					}
-					TORRENT_CATCH(std::bad_alloc&)
+					for (int i = 0; i < num_attempts; ++i)
 					{
-						// we ran out of memory trying to connect to a peer
+						TORRENT_TRY
-						// lower the global limit to the number of peers
+						{
-						// we already have
+							if (t.try_connect_peer())
-						m_settings.connections_limit = num_connections();
+							{
-						if (m_settings.connections_limit < 2) m_settings.connections_limit = 2;
+								--max_connections;
+								--free_slots;
+								steps_since_last_connect = 0;
+#ifdef TORRENT_STATS
+								++m_connection_attempts;
+#endif
+							}
+						}
+						TORRENT_CATCH(std::bad_alloc&)
+						{
+							// we ran out of memory trying to connect to a peer
+							// lower the global limit to the number of peers
+							// we already have
+							m_settings.connections_limit = num_connections();
+							if (m_settings.connections_limit < 2) m_settings.connections_limit = 2;
+						}
+						if (free_slots <= -m_half_open.limit()) break;
+						if (max_connections == 0) break;
+						if (num_connections() >= m_settings.connections_limit) break;
 					}
 				}
 

src/torrent.cpp

@@ -295,7 +295,6 @@ namespace libtorrent
 //		PRINT_OFFSETOF(torrent, m_seeding_time:24)
 		PRINT_OFFSETOF(torrent, m_time_scaler)
 //		PRINT_OFFSETOF(torrent, m_max_uploads:24)
-		PRINT_OFFSETOF(torrent, m_deficit_counter)
 //		PRINT_OFFSETOF(torrent, m_num_uploads:24)
 //		PRINT_OFFSETOF(torrent, m_block_size_shift:5)
 //		PRINT_OFFSETOF(torrent, m_has_incoming:1)
@@ -397,7 +396,7 @@ namespace libtorrent
 		, m_seeding_time(0)
 		, m_time_scaler(0)
 		, m_max_uploads((1<<24)-1)
-		, m_deficit_counter(0)
+		, m_save_resume_flags(0)
 		, m_num_uploads(0)
 		, m_block_size_shift(root2(block_size))
 		, m_has_incoming(false)
@@ -423,7 +422,6 @@ namespace libtorrent
 		, m_last_upload(0)
 		, m_downloaders(0xffffff)
 		, m_interface_index(0)
-		, m_save_resume_flags(0)
 		, m_graceful_pause_mode(false)
 		, m_need_connect_boost(true)
 		, m_lsd_seq(0)
@@ -7796,21 +7794,10 @@ namespace libtorrent
 	{
 		TORRENT_ASSERT(m_ses.is_network_thread());
 		TORRENT_ASSERT(want_more_peers());
-		if (m_deficit_counter < 100) return false;
-		m_deficit_counter -= 100;
 		bool ret = m_policy.connect_one_peer(m_ses.session_time());
 		return ret;
 	}
 
-	void torrent::give_connect_points(int points)
-	{
-		TORRENT_ASSERT(m_ses.is_network_thread());
-		TORRENT_ASSERT(points <= 200);
-		TORRENT_ASSERT(points > 0);
-		TORRENT_ASSERT(want_more_peers());
-		m_deficit_counter += points;
-	}
-
 	void torrent::add_peer(tcp::endpoint const& adr, int source)
 	{
 		TORRENT_ASSERT(m_ses.is_network_thread());