Change: [Linkgraph] Pause the game when linkgraph jobs lag (OpenTTD#6470

)

Check if the job is still running one date fract tick before it is due
to join and if so pause the game until its done.
This avoids the main thread being blocked on a thread join, which appears
to the user as if the game is unresponsive, as the UI does not repaint
and cannot be interacted with.
Show if pause is due to link graph job in status bar, update network
messages.
This does not apply for network clients.

src/lang/english.txt

@@ -771,6 +771,7 @@ STR_SMALLMAP_TOOLTIP_ENABLE_ALL_CARGOS                          :{BLACK}Display
 STR_STATUSBAR_TOOLTIP_SHOW_LAST_NEWS                            :{BLACK}Show last message or news report
 STR_STATUSBAR_COMPANY_NAME                                      :{SILVER}- -  {COMPANY}  - -
 STR_STATUSBAR_PAUSED                                            :{YELLOW}*  *  PAUSED  *  *
+STR_STATUSBAR_PAUSED_LINK_GRAPH                                 :{ORANGE}*  *  PAUSED (waiting for link graph update) *  *
 STR_STATUSBAR_AUTOSAVE                                          :{RED}AUTOSAVE
 STR_STATUSBAR_SAVING_GAME                                       :{RED}*  *  SAVING GAME  *  *
 
@@ -2186,11 +2187,13 @@ STR_NETWORK_SERVER_MESSAGE_GAME_STILL_PAUSED_1                  :Game still paus
 STR_NETWORK_SERVER_MESSAGE_GAME_STILL_PAUSED_2                  :Game still paused ({STRING}, {STRING})
 STR_NETWORK_SERVER_MESSAGE_GAME_STILL_PAUSED_3                  :Game still paused ({STRING}, {STRING}, {STRING})
 STR_NETWORK_SERVER_MESSAGE_GAME_STILL_PAUSED_4                  :Game still paused ({STRING}, {STRING}, {STRING}, {STRING})
+STR_NETWORK_SERVER_MESSAGE_GAME_STILL_PAUSED_5                  :Game still paused ({STRING}, {STRING}, {STRING}, {STRING}, {STRING})
 STR_NETWORK_SERVER_MESSAGE_GAME_UNPAUSED                        :Game unpaused ({STRING})
 STR_NETWORK_SERVER_MESSAGE_GAME_REASON_NOT_ENOUGH_PLAYERS       :number of players
 STR_NETWORK_SERVER_MESSAGE_GAME_REASON_CONNECTING_CLIENTS       :connecting clients
 STR_NETWORK_SERVER_MESSAGE_GAME_REASON_MANUAL                   :manual
 STR_NETWORK_SERVER_MESSAGE_GAME_REASON_GAME_SCRIPT              :game script
+STR_NETWORK_SERVER_MESSAGE_GAME_REASON_LINK_GRAPH               :waiting for link graph update
 ############ End of leave-in-this-order
 STR_NETWORK_MESSAGE_CLIENT_LEAVING                              :leaving
 STR_NETWORK_MESSAGE_CLIENT_JOINED                               :*** {RAW_STRING} has joined the game

src/linkgraph/linkgraphjob.cpp

@@ -40,7 +40,8 @@ LinkGraphJob::LinkGraphJob(const LinkGraph &orig) :
 		link_graph(orig),
 		settings(_settings_game.linkgraph),
 		thread(NULL),
-		join_date(_date + _settings_game.linkgraph.recalc_time)
+		join_date(_date + _settings_game.linkgraph.recalc_time),
+		job_completed(false)
 {
 }
 

src/linkgraph/linkgraphjob.h

@@ -15,6 +15,7 @@
 #include "../thread/thread.h"
 #include "linkgraph.h"
 #include <list>
+#include <atomic>
 
 class LinkGraphJob;
 class Path;
@@ -63,6 +64,7 @@ class LinkGraphJob : public LinkGraphJobPool::PoolItem<&_link_graph_job_pool>{
 	Date join_date;                   ///< Date when the job is to be joined.
 	NodeAnnotationVector nodes;       ///< Extra node data necessary for link graph calculation.
 	EdgeAnnotationMatrix edges;       ///< Extra edge data necessary for link graph calculation.
+	std::atomic<bool> job_completed;  ///< Is the job still running. This is accessed by multiple threads and reads may be stale.
 
 	void EraseFlows(NodeID from);
 	void JoinThread();
@@ -267,18 +269,25 @@ class LinkGraphJob : public LinkGraphJobPool::PoolItem<&_link_graph_job_pool>{
 	 * settings have to be brutally const-casted in order to populate them.
 	 */
 	LinkGraphJob() : settings(_settings_game.linkgraph), thread(NULL),
-			join_date(INVALID_DATE) {}
+			join_date(INVALID_DATE), job_completed(false) {}
 
 	LinkGraphJob(const LinkGraph &orig);
 	~LinkGraphJob();
 
 	void Init();
 
+	/**
+	 * Check if job has actually finished.
+	 * This is allowed to spuriously return an incorrect value.
+	 * @return True if job has actually finished.
+	 */
+	inline bool IsJobCompleted() const { return this->job_completed.load(std::memory_order_acquire); }
+
 	/**
 	 * Check if job is supposed to be finished.
 	 * @return True if job should be finished by now, false if not.
 	 */
-	inline bool IsFinished() const { return this->join_date <= _date; }
+	inline bool IsScheduledToBeJoined() const { return this->join_date <= _date; }
 
 	/**
 	 * Get the date when the job should be finished.

src/linkgraph/linkgraphschedule.cpp

@@ -16,6 +16,7 @@
 #include "mcf.h"
 #include "flowmapper.h"
 #include "../framerate_type.h"
+#include "../command_func.h"
 
 #include "../safeguards.h"
 
@@ -50,14 +51,24 @@ void LinkGraphSchedule::SpawnNext()
 	}
 }
 
+/**
+ * Join the next finished job, if available.
+ */
+bool LinkGraphSchedule::IsJoinWithUnfinishedJobDue() const
+{
+	if (this->running.empty()) return false;
+	const LinkGraphJob *next = this->running.front();
+	return next->IsScheduledToBeJoined() && !next->IsJobCompleted();
+}
+
 /**
  * Join the next finished job, if available.
  */
 void LinkGraphSchedule::JoinNext()
 {
 	if (this->running.empty()) return;
 	LinkGraphJob *next = this->running.front();
-	if (!next->IsFinished()) return;
+	if (!next->IsScheduledToBeJoined()) return;
 	this->running.pop_front();
 	LinkGraphID id = next->LinkGraphIndex();
 	delete next; // implicitly joins the thread
@@ -79,6 +90,18 @@ void LinkGraphSchedule::JoinNext()
 	for (uint i = 0; i < lengthof(instance.handlers); ++i) {
 		instance.handlers[i]->Run(*job);
 	}
+
+	/*
+	 * Readers of this variable in another thread may see an out of date value.
+	 * However this is OK as this will only happen just as a job is completing,
+	 * and the real synchronisation is provided by the thread join operation.
+	 * In the worst case the main thread will be paused for longer than
+	 * strictly necessary before joining.
+	 * This is just a hint variable to avoid performing the join excessively
+	 * early and blocking the main thread.
+	 */
+
+	job->job_completed.store(true, std::memory_order_release);
 }
 
 /**
@@ -141,6 +164,27 @@ LinkGraphSchedule::~LinkGraphSchedule()
 	}
 }
 
+/**
+ * Pause the game if on the next _date_fract tick, we would do a join with the next
+ * link graph job, but it is still running.
+ * If we previous paused, unpause if the job is now ready to be joined with
+ */
+void StateGameLoop_LinkGraphPauseControl()
+{
+	if (_pause_mode & PM_PAUSED_LINK_GRAPH) {
+		/* We are paused waiting on a job, check the job every tick */
+		if (!LinkGraphSchedule::instance.IsJoinWithUnfinishedJobDue()) {
+			DoCommandP(0, PM_PAUSED_LINK_GRAPH, 0, CMD_PAUSE);
+		}
+	} else if (_pause_mode == PM_UNPAUSED &&
+			_date_fract == LinkGraphSchedule::SPAWN_JOIN_TICK - 1 &&
+			_date % _settings_game.linkgraph.recalc_interval == _settings_game.linkgraph.recalc_interval / 2 &&
+			LinkGraphSchedule::instance.IsJoinWithUnfinishedJobDue()) {
+		/* perform check one _date_fract tick before we would join */
+		DoCommandP(0, PM_PAUSED_LINK_GRAPH, 1, CMD_PAUSE);
+	}
+}
+
 /**
  * Spawn or join a link graph job or compress a link graph if any link graph is
  * due to do so.

src/linkgraph/linkgraphschedule.h

@@ -57,6 +57,7 @@ class LinkGraphSchedule {
 	static void Clear();
 
 	void SpawnNext();
+	bool IsJoinWithUnfinishedJobDue() const;
 	void JoinNext();
 	void SpawnAll();
 	void ShiftDates(int interval);
@@ -78,4 +79,6 @@ class LinkGraphSchedule {
 	void Unqueue(LinkGraph *lg) { this->schedule.remove(lg); }
 };
 
+void StateGameLoop_LinkGraphPauseControl();
+
 #endif /* LINKGRAPHSCHEDULE_H */

src/misc_cmd.cpp

@@ -152,6 +152,7 @@ CommandCost CmdPause(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32 p2,
 		case PM_PAUSED_ERROR:
 		case PM_PAUSED_NORMAL:
 		case PM_PAUSED_GAME_SCRIPT:
+		case PM_PAUSED_LINK_GRAPH:
 			break;
 
 #ifdef ENABLE_NETWORK

src/network/network.cpp

@@ -353,7 +353,8 @@ void NetworkHandlePauseChange(PauseMode prev_mode, PauseMode changed_mode)
 		case PM_PAUSED_NORMAL:
 		case PM_PAUSED_JOIN:
 		case PM_PAUSED_GAME_SCRIPT:
-		case PM_PAUSED_ACTIVE_CLIENTS: {
+		case PM_PAUSED_ACTIVE_CLIENTS:
+		case PM_PAUSED_LINK_GRAPH: {
 			bool changed = ((_pause_mode == PM_UNPAUSED) != (prev_mode == PM_UNPAUSED));
 			bool paused = (_pause_mode != PM_UNPAUSED);
 			if (!paused && !changed) return;
@@ -366,13 +367,15 @@ void NetworkHandlePauseChange(PauseMode prev_mode, PauseMode changed_mode)
 				if ((_pause_mode & PM_PAUSED_JOIN) != PM_UNPAUSED)           SetDParam(++i, STR_NETWORK_SERVER_MESSAGE_GAME_REASON_CONNECTING_CLIENTS);
 				if ((_pause_mode & PM_PAUSED_GAME_SCRIPT) != PM_UNPAUSED)    SetDParam(++i, STR_NETWORK_SERVER_MESSAGE_GAME_REASON_GAME_SCRIPT);
 				if ((_pause_mode & PM_PAUSED_ACTIVE_CLIENTS) != PM_UNPAUSED) SetDParam(++i, STR_NETWORK_SERVER_MESSAGE_GAME_REASON_NOT_ENOUGH_PLAYERS);
+				if ((_pause_mode & PM_PAUSED_LINK_GRAPH) != PM_UNPAUSED)     SetDParam(++i, STR_NETWORK_SERVER_MESSAGE_GAME_REASON_LINK_GRAPH);
 				str = STR_NETWORK_SERVER_MESSAGE_GAME_STILL_PAUSED_1 + i;
 			} else {
 				switch (changed_mode) {
 					case PM_PAUSED_NORMAL:         SetDParam(0, STR_NETWORK_SERVER_MESSAGE_GAME_REASON_MANUAL); break;
 					case PM_PAUSED_JOIN:           SetDParam(0, STR_NETWORK_SERVER_MESSAGE_GAME_REASON_CONNECTING_CLIENTS); break;
 					case PM_PAUSED_GAME_SCRIPT:    SetDParam(0, STR_NETWORK_SERVER_MESSAGE_GAME_REASON_GAME_SCRIPT); break;
 					case PM_PAUSED_ACTIVE_CLIENTS: SetDParam(0, STR_NETWORK_SERVER_MESSAGE_GAME_REASON_NOT_ENOUGH_PLAYERS); break;
+					case PM_PAUSED_LINK_GRAPH:     SetDParam(0, STR_NETWORK_SERVER_MESSAGE_GAME_REASON_LINK_GRAPH); break;
 					default: NOT_REACHED();
 				}
 				str = paused ? STR_NETWORK_SERVER_MESSAGE_GAME_PAUSED : STR_NETWORK_SERVER_MESSAGE_GAME_UNPAUSED;

src/openttd.cpp

@@ -1349,6 +1349,10 @@ static void CheckCaches()
  */
 void StateGameLoop()
 {
+	if (!_networking || _network_server) {
+		StateGameLoop_LinkGraphPauseControl();
+	}
+
 	/* don't execute the state loop during pause */
 	if (_pause_mode != PM_UNPAUSED) {
 		PerformanceMeasurer::Paused(PFE_GAMELOOP);

src/openttd.h

@@ -62,6 +62,7 @@ enum PauseMode {
 	PM_PAUSED_ERROR          = 1 << 3, ///< A game paused because a (critical) error
 	PM_PAUSED_ACTIVE_CLIENTS = 1 << 4, ///< A game paused for 'min_active_clients'
 	PM_PAUSED_GAME_SCRIPT    = 1 << 5, ///< A game paused by a game script
+	PM_PAUSED_LINK_GRAPH     = 1 << 6, ///< A game paused due to the link graph schedule lagging
 
 	/** Pause mode bits when paused for network reasons. */
 	PMB_PAUSED_NETWORK = PM_PAUSED_ACTIVE_CLIENTS | PM_PAUSED_JOIN,

src/statusbar_gui.cpp

@@ -163,7 +163,8 @@ struct StatusBarWindow : Window {
 				} else if (_do_autosave) {
 					DrawString(r.left + WD_FRAMERECT_LEFT, r.right - WD_FRAMERECT_RIGHT, r.top + WD_FRAMERECT_TOP, STR_STATUSBAR_AUTOSAVE, TC_FROMSTRING, SA_HOR_CENTER);
 				} else if (_pause_mode != PM_UNPAUSED) {
-					DrawString(r.left + WD_FRAMERECT_LEFT, r.right - WD_FRAMERECT_RIGHT, r.top + WD_FRAMERECT_TOP, STR_STATUSBAR_PAUSED, TC_FROMSTRING, SA_HOR_CENTER);
+					StringID msg = (_pause_mode & PM_PAUSED_LINK_GRAPH) ? STR_STATUSBAR_PAUSED_LINK_GRAPH : STR_STATUSBAR_PAUSED;
+					DrawString(r.left + WD_FRAMERECT_LEFT, r.right - WD_FRAMERECT_RIGHT, r.top + WD_FRAMERECT_TOP, msg, TC_FROMSTRING, SA_HOR_CENTER);
 				} else if (this->ticker_scroll < TICKER_STOP && FindWindowById(WC_NEWS_WINDOW, 0) == NULL && _statusbar_news_item != NULL && _statusbar_news_item->string_id != 0) {
 					/* Draw the scrolling news text */
 					if (!DrawScrollingStatusText(_statusbar_news_item, this->ticker_scroll, r.left + WD_FRAMERECT_LEFT, r.right - WD_FRAMERECT_RIGHT, r.top + WD_FRAMERECT_TOP, r.bottom)) {