disk write queue watermark fix

examples/client_test.cpp

@@ -506,9 +506,11 @@ void print_peer_info(std::string& out, std::vector<libtorrent::peer_info> const&
 			, (i->flags & peer_info::on_parole)?'p':'.'
 			, (i->flags & peer_info::optimistic_unchoke)?'O':'.'
 			, (i->read_state == peer_info::bw_limit)?'r':
-				(i->read_state == peer_info::bw_network)?'R':'.'
+				(i->read_state == peer_info::bw_network)?'R':
+				(i->read_state == peer_info::bw_disk)?'D':'.'
 			, (i->write_state == peer_info::bw_limit)?'w':
-				(i->write_state == peer_info::bw_network)?'W':'.'
+				(i->write_state == peer_info::bw_network)?'W':
+				(i->write_state == peer_info::bw_disk)?'D':'.'
 			, (i->flags & peer_info::snubbed)?'S':'.'
 			, (i->flags & peer_info::upload_only)?'U':'D'
 			, (i->flags & peer_info::endgame_mode)?'-':'.'

include/libtorrent/aux_/session_impl.hpp

@@ -423,6 +423,9 @@ namespace libtorrent
 				, int source_type, address const& source);
 			address const& external_address() const { return m_external_address; }
 
+			bool can_write_to_disk() const
+			{ return m_disk_thread.can_write(); }
+
 			// used when posting synchronous function
 			// calls to session_impl and torrent objects
 			mutable libtorrent::mutex mut;

include/libtorrent/disk_io_thread.hpp

@@ -303,6 +303,7 @@ namespace libtorrent
 		// this is used to slow down the download global download
 		// speed when the queue buffer size is too big.
 		size_type queue_buffer_size() const;
+		bool can_write() const;
 
 		void get_cache_info(sha1_hash const& ih
 			, std::vector<cached_piece_info>& ret) const;

include/libtorrent/storage.hpp

@@ -215,8 +215,6 @@ namespace libtorrent
 		
 		void async_check_files(boost::function<void(int, disk_io_job const&)> const& handler);
 
-		int queued_bytes() const;
-
 		void async_rename_file(int index, std::string const& name
 			, boost::function<void(int, disk_io_job const&)> const& handler);
 

src/disk_io_thread.cpp

@@ -321,6 +321,7 @@ namespace libtorrent
 		, m_queue_buffer_size(0)
 		, m_last_file_check(time_now_hires())
 		, m_physical_ram(0)
+		, m_exceeded_write_queue(false)
 		, m_ios(ios)
 		, m_queue_callback(queue_callback)
 		, m_work(io_service::work(m_ios))
@@ -356,6 +357,12 @@ namespace libtorrent
 		m_jobs.clear();
 	}
 
+	bool disk_io_thread::can_write() const
+	{
+		mutex::scoped_lock l(m_queue_mutex);
+		return !m_exceeded_write_queue;
+	}
+
 	void disk_io_thread::get_cache_info(sha1_hash const& ih, std::vector<cached_piece_info>& ret) const
 	{
 		mutex::scoped_lock l(m_piece_mutex);
@@ -1623,14 +1630,15 @@ namespace libtorrent
 					if (m_exceeded_write_queue)
 					{
 						int low_watermark = m_settings.max_queued_disk_bytes_low_watermark == 0
-							? m_settings.max_queued_disk_bytes * 3 / 4
+							? m_settings.max_queued_disk_bytes / 2
 							: m_settings.max_queued_disk_bytes_low_watermark;
 						if (low_watermark >= m_settings.max_queued_disk_bytes)
-							low_watermark = m_settings.max_queued_disk_bytes * 3 / 4;
+							low_watermark = m_settings.max_queued_disk_bytes / 2;
 
 						if (m_queue_buffer_size < low_watermark
-							|| m_settings.max_queued_disk_bytes > 0)
+							|| m_settings.max_queued_disk_bytes == 0)
 						{
+							m_exceeded_write_queue = false;
 							// we just dropped below the high watermark of number of bytes
 							// queued for writing to the disk. Notify the session so that it
 							// can trigger all the connections waiting for this event
@@ -1734,7 +1742,10 @@ namespace libtorrent
 				, operation_has_buffer(j) ? j.buffer : 0);
 
 			if (post && m_queue_callback)
+			{
+				TORRENT_ASSERT(m_exceeded_write_queue == false);
 				m_ios.post(m_queue_callback);
+			}
 
 			flush_expired_pieces();
 

src/peer_connection.cpp

@@ -2410,7 +2410,7 @@ namespace libtorrent
 		TORRENT_ASSERT(m_channel_state[download_channel] == peer_info::bw_idle);
 		m_download_queue.erase(b);
 
-		if (t->filesystem().queued_bytes() >= m_ses.settings().max_queued_disk_bytes
+		if (!m_ses.can_write_to_disk()
 			&& m_ses.settings().max_queued_disk_bytes
 			&& t->alerts().should_post<performance_alert>()
 			&& (now - m_ses.m_last_disk_performance_warning) > seconds(10))
@@ -5064,8 +5064,7 @@ namespace libtorrent
 		if (!bw_limit) return false;
 
 		bool disk = m_ses.settings().max_queued_disk_bytes == 0
-			|| !t || t->get_storage() == 0
-			|| t->filesystem().queued_bytes() < m_ses.settings().max_queued_disk_bytes
+			|| m_ses.can_write_to_disk()
 			// don't block this peer because of disk saturation
 			// if we're not downloading any pieces from it
 			|| m_outstanding_bytes == 0;

src/storage.cpp

@@ -1626,11 +1626,6 @@ ret:
 #endif
 	}
 
-	int piece_manager::queued_bytes() const
-	{
-		return m_io_thread.queue_buffer_size();
-	}
-
 	void piece_manager::async_write(
 		peer_request const& r
 		, disk_buffer_holder& buffer