add a separate setting for max peer list size for paused torrents

docs/manual.rst

@@ -3707,6 +3707,11 @@ this limit, and once the size hits the limit, peers are no longer
 added to the list. If this limit is set to 0, there is no limit on
 how many peers we'll keep in the peer list.
 
+``max_paused_peerlist_size`` is the max peer list size used for torrents
+that are paused. This default to the same as ``max_peerlist_size``, but
+can be used to save memory for paused torrents, since it's not as
+important for them to keep a large peer list.
+
 ``min_announce_interval`` is the minimum allowed announce interval
 for a tracker. This is specified in seconds, defaults to 5 minutes and
 is used as a sanity check on what is returned from a tracker. It

examples/client_test.cpp

@@ -754,7 +754,7 @@ int main(int argc, char* argv[])
 	}
 
 	using namespace libtorrent;
-	session_settings settings;
+	session_settings settings = min_memory_usage();
 	proxy_settings ps;
 
 	settings.user_agent = "client_test/" LIBTORRENT_VERSION;

include/libtorrent/session_settings.hpp

@@ -145,6 +145,7 @@ namespace libtorrent
 			, auto_scrape_interval(1800)
 			, auto_scrape_min_interval(300)
 			, max_peerlist_size(8000)
+			, max_paused_peerlist_size(8000)
 			, min_announce_interval(5 * 60)
 			, prioritize_partial_pieces(false)
 			, auto_manage_startup(120)
@@ -483,6 +484,10 @@ namespace libtorrent
 		// about, not necessarily connected to.
 		int max_peerlist_size;
 
+		// when a torrent is paused, this is the max peer
+		// list size that's used
+		int max_paused_peerlist_size;
+
 		// any announce intervals reported from a tracker
 		// that is lower than this, will be clamped to this
 		// value. It's specified in seconds

src/policy.cpp

@@ -429,17 +429,18 @@ namespace libtorrent
 		return pe.connection == 0
 			&& pe.last_connected != 0
 			&& !pe.banned
-			&& !is_connect_candidate(pe, m_finished)
-			&& m_peers.size() >= m_torrent->settings().max_peerlist_size * 0.95
-			&& m_torrent->settings().max_peerlist_size > 0;
+			&& !is_connect_candidate(pe, m_finished);
 	}
 
 	void policy::erase_peers()
 	{
 		INVARIANT_CHECK;
 
-		if (m_torrent->settings().max_peerlist_size == 0
-			|| m_peers.empty()) return;
+		int max_peerlist_size = m_torrent->is_paused()
+			?m_torrent->settings().max_paused_peerlist_size
+			:m_torrent->settings().max_peerlist_size;
+
+		if (max_peerlist_size == 0 || m_peers.empty()) return;
 
 		int erase_candidate = -1;
 
@@ -450,7 +451,7 @@ namespace libtorrent
 		for (int iterations = (std::min)(int(m_peers.size()), 300);
 			iterations > 0; --iterations)
 		{
-			if (m_peers.size() < m_torrent->settings().max_peerlist_size * 0.95)
+			if (m_peers.size() < max_peerlist_size * 0.95)
 				break;
 
 			if (round_robin == m_peers.size()) round_robin = 0;
@@ -525,6 +526,10 @@ namespace libtorrent
 		bool pinged = false;
 #endif
 
+		int max_peerlist_size = m_torrent->is_paused()
+			?m_torrent->settings().max_paused_peerlist_size
+			:m_torrent->settings().max_peerlist_size;
+
 		for (int iterations = (std::min)(int(m_peers.size()), 300);
 			iterations > 0; --iterations)
 		{
@@ -549,8 +554,8 @@ namespace libtorrent
 			// if the number of peers is growing large
 			// we need to start weeding.
 
-			if (m_peers.size() >= m_torrent->settings().max_peerlist_size * 0.95
-				&& m_torrent->settings().max_peerlist_size > 0)
+			if (m_peers.size() >= max_peerlist_size * 0.95
+				&& max_peerlist_size > 0)
 			{
 				if (is_erase_candidate(pe, m_finished)
 					&& (erase_candidate == -1
@@ -663,6 +668,7 @@ namespace libtorrent
 		// override at a time
 		error_code ec;
 		TORRENT_ASSERT(c.remote() == c.get_socket()->remote_endpoint(ec) || ec);
+		TORRENT_ASSERT(!m_torrent->is_paused());
 
 		aux::session_impl& ses = m_torrent->session();
 		
@@ -895,6 +901,10 @@ namespace libtorrent
 		iterator iter;
 		peer* i = 0;
 
+		int max_peerlist_size = m_torrent->is_paused()
+			?m_torrent->settings().max_paused_peerlist_size
+			:m_torrent->settings().max_peerlist_size;
+
 		bool found = false;
 		if (m_torrent->settings().allow_multiple_connections_per_ip)
 		{
@@ -913,13 +923,13 @@ namespace libtorrent
 
 		if (!found)
 		{
-			if (m_torrent->settings().max_peerlist_size
-				&& int(m_peers.size()) >= m_torrent->settings().max_peerlist_size)
+			if (max_peerlist_size
+				&& int(m_peers.size()) >= max_peerlist_size)
 			{
 				if (src == peer_info::resume_data) return 0;
 
 				erase_peers();
-				if (int(m_peers.size()) >= m_torrent->settings().max_peerlist_size)
+				if (int(m_peers.size()) >= max_peerlist_size)
 					return 0;
 
 				// since some peers were removed, we need to

src/session.cpp

@@ -154,6 +154,7 @@ namespace libtorrent
 		set.close_redundant_connections = true;
 
 		set.max_peerlist_size = 500;
+		set.max_paused_peerlist_size = 50;
 
 		// udp trackers are cheaper to talk to
 		set.prefer_udp_trackers = true;

src/torrent.cpp

@@ -4826,6 +4826,27 @@ namespace libtorrent
 		}
 #endif
 
+		m_time_scaler--;
+		if (m_time_scaler <= 0)
+		{
+			m_time_scaler = 10;
+
+			if (settings().max_sparse_regions > 0
+				&& m_picker
+				&& m_picker->sparse_regions() > settings().max_sparse_regions)
+			{
+				// we have too many sparse regions. Prioritize pieces
+				// that won't introduce new sparse regions
+				// prioritize pieces that will reduce the number of sparse
+				// regions even higher
+				int start = m_picker->cursor();
+				int end = m_picker->reverse_cursor();
+				for (int i = start; i < end; ++i)
+					update_sparse_piece_prio(i, start, end);
+			}
+			m_policy.pulse();
+		}
+
 		if (is_paused())
 		{
 			// let the stats fade out to 0
@@ -4940,27 +4961,6 @@ namespace libtorrent
 		m_total_uploaded += m_stat.last_payload_uploaded();
 		m_total_downloaded += m_stat.last_payload_downloaded();
 		m_stat.second_tick(tick_interval);
-
-		m_time_scaler--;
-		if (m_time_scaler <= 0)
-		{
-			m_time_scaler = 10;
-
-			if (settings().max_sparse_regions > 0
-				&& m_picker
-				&& m_picker->sparse_regions() > settings().max_sparse_regions)
-			{
-				// we have too many sparse regions. Prioritize pieces
-				// that won't introduce new sparse regions
-				// prioritize pieces that will reduce the number of sparse
-				// regions even higher
-				int start = m_picker->cursor();
-				int end = m_picker->reverse_cursor();
-				for (int i = start; i < end; ++i)
-					update_sparse_piece_prio(i, start, end);
-			}
-			m_policy.pulse();
-		}
 	}
 
 	void torrent::request_time_critical_pieces()