log outstanding reading bytes from peers in stats log

include/libtorrent/peer_connection.hpp

@@ -608,6 +608,8 @@ namespace libtorrent
 		// start downloading payload again
 		void on_disk();
 
+		int num_reading_bytes() const { return m_reading_bytes; }
+
 		enum sync_t { read_async, read_sync };
 		void setup_receive(sync_t sync = read_sync);
 

parse_session_stats.py

@@ -142,6 +142,7 @@ reports = [
 	('disk_readback', '% of written blocks', '%%', 'portion of written blocks that had to be read back for hash verification', ['% read back']),
 	('disk_queue', 'number of queued disk jobs', '', 'queued disk jobs', ['disk queue size', 'disk read queue size', 'read job queue size limit']),
 	('disk_iops', 'operations/s', '', 'number of disk operations per second', ['read ops/s', 'write ops/s', 'smooth read ops/s', 'smooth write ops/s']),
+	('disk pending reads', 'Bytes', '', 'number of bytes peers are waiting for to be read from the disk', ['pending reading bytes']),
 	('mixed mode', 'rate', 'B/s', 'rates by transport protocol', ['TCP up rate','TCP down rate','uTP up rate','uTP down rate','TCP up limit','TCP down limit']),
 	('uTP delay', 'buffering delay', 's', 'network delays measured by uTP', ['uTP peak send delay','uTP avg send delay']),
 	('uTP delay histogram', 'buffering delay', 's', 'network delays measured by uTP', ['uTP avg send delay'], True),

src/session_impl.cpp

@@ -1042,6 +1042,7 @@ namespace aux {
 			":page faults"
 			":smooth read ops/s"
 			":smooth write ops/s"
+			":pending reading bytes"
 			"\n\n", m_stats_logger);
 	}
 #endif
@@ -3277,6 +3278,7 @@ namespace aux {
 		int peers_down_unchoked = 0;
 		int peers_up_unchoked = 0;
 		int num_end_game_peers = 0;
+		int reading_bytes = 0;
 		for (connection_map::iterator i = m_connections.begin()
 			, end(m_connections.end()); i != end; ++i)
 		{
@@ -3296,6 +3298,7 @@ namespace aux {
 			if (p->send_buffer_size() > 100 || !p->upload_queue().empty())
 				++peers_up_requests;
 			if (p->endgame()) ++num_end_game_peers;
+			reading_bytes += p->num_reading_bytes();
 
 			int dl_bucket = 0;
 			int dl_rate = p->statistics().download_payload_rate();
@@ -3488,6 +3491,8 @@ namespace aux {
 			STAT_LOG(d, m_read_ops.mean());
 			STAT_LOG(d, m_write_ops.mean());
 
+			STAT_LOG(d, reading_bytes);
+
 			fprintf(m_stats_logger, "\n");
 
 #undef STAT_LOG