added auto-sequential feature

ChangeLog

@@ -1,3 +1,4 @@
+	* added auto-sequential feature. download well-seeded torrents in-order
 	* removed built-in GeoIP support (this functionality is orthogonal to libtorrent)
 	* deprecate proxy settings in favor of regular settings
 	* deprecate separate settings for peer protocol encryption

include/libtorrent/aux_/session_impl.hpp

@@ -672,6 +672,7 @@ namespace libtorrent
 			void update_outgoing_interfaces();
 			void update_listen_interfaces();
 			void update_privileged_ports();
+			void update_auto_sequential();
 
 			void update_upnp();
 			void update_natpmp();

include/libtorrent/settings_pack.hpp

@@ -619,6 +619,12 @@ namespace libtorrent
 			// configured proxy, if any.
 			proxy_peer_connections,
 
+			// if this setting is true, torrents with a very high availability
+			// of pieces (and seeds) are downloaded sequentially. This is more
+			// efficient for the disk I/O. With many seeds, the download order
+			// is unlikely to matter anyway
+			auto_sequential,
+
 			max_bool_setting_internal,
 			num_bool_settings = max_bool_setting_internal - bool_type_base
 		};

include/libtorrent/torrent.hpp

@@ -375,7 +375,8 @@ namespace libtorrent
 
 		void new_external_ip();
 
-		torrent_status::state_t state() const { return (torrent_status::state_t)m_state; }
+		torrent_status::state_t state() const
+		{ return (torrent_status::state_t)m_state; }
 		void set_state(torrent_status::state_t s);
 
 		aux::session_settings const& settings() const;
@@ -383,7 +384,7 @@ namespace libtorrent
 	
 		void set_sequential_download(bool sd);
 		bool is_sequential_download() const
-		{ return m_sequential_download; }
+		{ return m_sequential_download || m_auto_sequential; }
 	
 		void queue_up();
 		void queue_down();
@@ -625,6 +626,7 @@ namespace libtorrent
 		// the number of peers that belong to this torrent
 		int num_peers() const { return (int)m_connections.size(); }
 		int num_seeds() const;
+		int num_downloaders() const;
 
 		typedef std::vector<peer_connection*>::iterator peer_iterator;
 		typedef std::vector<peer_connection*>::const_iterator const_peer_iterator;
@@ -643,6 +645,7 @@ namespace libtorrent
 
 		void add_suggest_piece(int piece);
 		void update_suggest_piece(int index, int change);
+		void update_auto_sequential();
 		void refresh_suggest_pieces();
 		void do_refresh_suggest_pieces();
 		void on_cache_info(disk_io_job const* j);
@@ -1611,7 +1614,11 @@ namespace libtorrent
 		// at high enough rates, it's inactive.
 		bool m_inactive:1;
 
-		// TODO: there's space for 1 bits here
+		// this is set if the auto_sequential setting is true and this swarm
+		// satisfies the criteria to be considered high-availability. i.e. if
+		// there's mostly seeds in the swarm, download the files sequentially
+		// for improved disk I/O performance.
+		bool m_auto_sequential:1;
 
 // ----
 

src/peer_connection.cpp

@@ -6945,7 +6945,8 @@ namespace libtorrent
 		// if m_num_pieces == 0, we probably don't have the
 		// metadata yet.
 		boost::shared_ptr<torrent> t = m_torrent.lock();
-		return m_num_pieces == (int)m_have_piece.size() && m_num_pieces > 0 && t && t->valid_metadata();
+		return m_num_pieces == (int)m_have_piece.size()
+			&& m_num_pieces > 0 && t && t->valid_metadata();
 	}
 
 	void peer_connection::set_share_mode(bool u)

src/session_impl.cpp

@@ -6188,6 +6188,13 @@ retry:
 		}
 	}
 
+	void session_impl::update_auto_sequential()
+	{
+		for (torrent_map::iterator i = m_torrents.begin()
+			, end(m_torrents.end()); i != end; ++i)
+			i->second->update_auto_sequential();
+	}
+
 	void session_impl::update_proxy()
 	{
 		// in case we just set a socks proxy, we might have to

src/settings_pack.cpp

@@ -200,6 +200,7 @@ namespace libtorrent
 		SET_NOPREV(prefer_rc4, false, 0),
 		SET_NOPREV(proxy_hostnames, true, 0),
 		SET_NOPREV(proxy_peer_connections, true, 0),
+		SET_NOPREV(auto_sequential, true, &session_impl::update_auto_sequential),
 	};
 
 	int_setting_entry_t int_settings[settings_pack::num_int_settings] =

src/torrent.cpp

@@ -3110,6 +3110,8 @@ namespace libtorrent
 		m_incomplete = incomplete;
 		m_downloaded = downloaded;
 
+		update_auto_sequential();
+
 		// these numbers are cached in the resume data
 		m_need_save_resume_data = true;
 	}
@@ -3306,6 +3308,31 @@ namespace libtorrent
 		state_updated();
 	}
 
+	void torrent::update_auto_sequential()
+	{
+		if (!m_ses.settings().get_bool(settings_pack::auto_sequential))
+		{
+			m_auto_sequential = false;
+			return;
+		}
+
+		if (int(m_connections.size()) - m_num_connecting < 10)
+		{
+			// there are too few peers. Be conservative and don't assume it's
+			// well seeded until we can connect to more peers
+			m_auto_sequential = false;
+			return;
+		}
+
+		// if there are at least 10 seeds, and there are 10 times more
+		// seeds than downloaders, enter sequential download mode
+		// (for performance)
+		int downloaders = num_downloaders();
+		int seeds = num_seeds();
+		m_auto_sequential = downloaders * 10 <= seeds
+			&& seeds > 9;
+	}
+
 	void torrent::do_connect_boost()
 	{
 		if (!m_need_connect_boost) return;
@@ -10657,6 +10684,7 @@ namespace libtorrent
 	{
 		need_policy();
 		m_policy->set_seed(p, s);
+		update_auto_sequential();
 	}
 
 	void torrent::clear_failcount(torrent_peer* p)
@@ -11322,6 +11350,8 @@ namespace libtorrent
 		m_stats_counters.inc_stats_counter(counters::recv_failed_bytes, b);
 	}
 
+	// TODO: 3 make this a gauge that's kept up to date rather than counting
+	// every time
 	int torrent::num_seeds() const
 	{
 		TORRENT_ASSERT(is_single_thread());
@@ -11334,6 +11364,20 @@ namespace libtorrent
 		return ret;
 	}
 
+	// TODO: 3 make this a gauge that's kept up to date rather than counting
+	// every time
+	int torrent::num_downloaders() const
+	{
+		TORRENT_ASSERT(is_single_thread());
+		INVARIANT_CHECK;
+
+		int ret = 0;
+		for (const_peer_iterator i = m_connections.begin()
+			, end(m_connections.end()); i != end; ++i)
+			if ((*i)->is_connected() && !(*i)->is_seed()) ++ret;
+		return ret;
+	}
+
 	void torrent::tracker_request_error(tracker_request const& r
 		, int response_code, error_code const& ec, const std::string& msg
 		, int retry_interval)