Paper/Spigot-Server-Patches/0021-Further-improve-server-tick-loop.patch

From 98a06688336bb1b699ef02030dd393fff7fe597f Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Tue, 1 Mar 2016 23:09:29 -0600
Subject: [PATCH] Further improve server tick loop

Improves how the catchup buffer is handled, allowing it to roll both ways
increasing the effeciency of the thread sleep so it only will sleep once.

Also increases the buffer of the catchup to ensure server stays at 20 TPS unless extreme conditions

Previous implementation did not calculate TPS correctly.
Switch to a realistic rolling average and factor in std deviation as an extra reporting variable

diff --git a/src/main/java/net/minecraft/server/MinecraftServer.java b/src/main/java/net/minecraft/server/MinecraftServer.java
index c8c6959..127d11c 100644
--- a/src/main/java/net/minecraft/server/MinecraftServer.java
+++ b/src/main/java/net/minecraft/server/MinecraftServer.java
@@ -112,17 +112,11 @@ public abstract class MinecraftServer implements Runnable, ICommandListener, IAs
     public org.bukkit.command.ConsoleCommandSender console;
     public org.bukkit.command.RemoteConsoleCommandSender remoteConsole;
     public ConsoleReader reader;
-    public static int currentTick = (int) (System.currentTimeMillis() / 50);
+    public static int currentTick = 0; // Paper - Further improve tick loop
     public final Thread primaryThread;
     public java.util.Queue<Runnable> processQueue = new java.util.concurrent.ConcurrentLinkedQueue<Runnable>();
     public int autosavePeriod;
     // CraftBukkit end
-    // Spigot start
-    private static final int TPS = 20;
-    private static final int TICK_TIME = 1000000000 / TPS;
-    private static final int SAMPLE_INTERVAL = 100;
-    public final double[] recentTps = new double[ 3 ];
-    // Spigot end
 
     public MinecraftServer(OptionSet options, Proxy proxy, DataConverterManager dataconvertermanager, YggdrasilAuthenticationService yggdrasilauthenticationservice, MinecraftSessionService minecraftsessionservice, GameProfileRepository gameprofilerepository, UserCache usercache) {
         io.netty.util.ResourceLeakDetector.setEnabled( false ); // Spigot - disable
@@ -531,12 +525,54 @@ public abstract class MinecraftServer implements Runnable, ICommandListener, IAs
         this.isRunning = false;
     }
 
-    // Spigot Start
-    private static double calcTps(double avg, double exp, double tps)
-    {
-        return ( avg * exp ) + ( tps * ( 1 - exp ) );
+    // Paper start - Further improve server tick loop
+    private static final int TPS = 20;
+    private static final long SEC_IN_NANO = 1000000000;
+    private static final long TICK_TIME = SEC_IN_NANO / TPS;
+    private static final long MAX_CATCHUP_BUFFER = TICK_TIME * TPS * 60L;
+    private static final int SAMPLE_INTERVAL = 20;
+    public final RollingAverage tps1 = new RollingAverage(60);
+    public final RollingAverage tps5 = new RollingAverage(60 * 5);
+    public final RollingAverage tps15 = new RollingAverage(60 * 15);
+    public double[] recentTps = new double[3]; // Paper - Fine have your darn compat with bad plugins
+
+    public static class RollingAverage {
+        private final int size;
+        private long time;
+        private double total;
+        private int index = 0;
+        private final double[] samples;
+        private final long[] times;
+
+        RollingAverage(int size) {
+            this.size = size;
+            this.time = size * SEC_IN_NANO;
+            this.total = TPS * SEC_IN_NANO * size;
+            this.samples = new double[size];
+            this.times = new long[size];
+            for (int i = 0; i < size; i++) {
+                this.samples[i] = TPS;
+                this.times[i] = SEC_IN_NANO;
+            }
+        }
+
+        public void add(double x, long t) {
+            time -= times[index];
+            total -= samples[index] * times[index];
+            samples[index] = x;
+            times[index] = t;
+            time += t;
+            total += x * t;
+            if (++index == size) {
+                index = 0;
+            }
+        }
+
+        public double getAverage() {
+            return total / time;
+        }
     }
-    // Spigot End
+    // Paper End
  
     public void run() {
         try {
@@ -550,24 +586,41 @@ public abstract class MinecraftServer implements Runnable, ICommandListener, IAs
 
                 // Spigot start
                 Arrays.fill( recentTps, 20 );
-                long lastTick = System.nanoTime(), catchupTime = 0, curTime, wait, tickSection = lastTick;
+                long start = System.nanoTime(), lastTick = start - TICK_TIME, catchupTime = 0, curTime, wait, tickSection = start; // Paper - Further improve server tick loop
                 while (this.isRunning) {
                     curTime = System.nanoTime();
-                    wait = TICK_TIME - (curTime - lastTick) - catchupTime;
+                    // Paper start - Further improve server tick loop
+                    wait = TICK_TIME - (curTime - lastTick);
+                    if (wait > 0) {
+                        if (catchupTime < 2E6) {
+                            wait += Math.abs(catchupTime);
+                        }
+                        if (wait < catchupTime) {
+                            catchupTime -= wait;
+                            wait = 0;
+                        } else if (catchupTime > 2E6) {
+                            wait -= catchupTime;
+                            catchupTime -= catchupTime;
+                        }
+                    }
                     if (wait > 0) {
                         Thread.sleep(wait / 1000000);
-                        catchupTime = 0;
-                        continue;
-                    } else {
-                        catchupTime = Math.min(1000000000, Math.abs(wait));
+                        wait = TICK_TIME - (curTime - lastTick);
                     }
 
-                    if ( MinecraftServer.currentTick++ % SAMPLE_INTERVAL == 0 )
+                    catchupTime = Math.min(MAX_CATCHUP_BUFFER, catchupTime - wait);
+                    if ( ++MinecraftServer.currentTick % SAMPLE_INTERVAL == 0 )
                     {
-                        double currentTps = 1E9 / ( curTime - tickSection ) * SAMPLE_INTERVAL;
-                        recentTps[0] = calcTps( recentTps[0], 0.92, currentTps ); // 1/exp(5sec/1min)
-                        recentTps[1] = calcTps( recentTps[1], 0.9835, currentTps ); // 1/exp(5sec/5min)
-                        recentTps[2] = calcTps( recentTps[2], 0.9945, currentTps ); // 1/exp(5sec/15min)
+                        final long diff = curTime - tickSection;
+                        double currentTps = 1E9 / diff * SAMPLE_INTERVAL;
+                        tps1.add(currentTps, diff);
+                        tps5.add(currentTps, diff);
+                        tps15.add(currentTps, diff);
+                        // Backwards compat with bad plugins
+                        recentTps[0] = tps1.getAverage();
+                        recentTps[1] = tps5.getAverage();
+                        recentTps[2] = tps15.getAverage();
+                        // Paper end
                         tickSection = curTime;
                     }
                     lastTick = curTime;
diff --git a/src/main/java/org/bukkit/craftbukkit/CraftServer.java b/src/main/java/org/bukkit/craftbukkit/CraftServer.java
index 9113be9..c1149a6 100644
--- a/src/main/java/org/bukkit/craftbukkit/CraftServer.java
+++ b/src/main/java/org/bukkit/craftbukkit/CraftServer.java
@@ -1726,6 +1726,17 @@ public final class CraftServer implements Server {
         return CraftMagicNumbers.INSTANCE;
     }
 
+    // Paper - Add getTPS API - Further improve tick loop
+    @Override
+    public double[] getTPS() {
+        return new double[] {
+                MinecraftServer.getServer().tps1.getAverage(),
+                MinecraftServer.getServer().tps5.getAverage(),
+                MinecraftServer.getServer().tps15.getAverage()
+        };
+    }
+    // Paper end
+
     private final Spigot spigot = new Spigot()
     {
 
diff --git a/src/main/java/org/spigotmc/TicksPerSecondCommand.java b/src/main/java/org/spigotmc/TicksPerSecondCommand.java
index be2e31d..6d21c32 100644
--- a/src/main/java/org/spigotmc/TicksPerSecondCommand.java
+++ b/src/main/java/org/spigotmc/TicksPerSecondCommand.java
@@ -1,8 +1,5 @@
 package org.spigotmc;
 
-import com.google.common.base.Joiner;
-import net.minecraft.server.MinecraftServer;
-import com.google.common.collect.Iterables;
 import org.bukkit.ChatColor;
 import org.bukkit.command.Command;
 import org.bukkit.command.CommandSender;
@@ -26,18 +23,20 @@ public class TicksPerSecondCommand extends Command
             return true;
         }
 
-        StringBuilder sb = new StringBuilder( ChatColor.GOLD + "TPS from last 1m, 5m, 15m: " );
-        for ( double tps : MinecraftServer.getServer().recentTps )
-        {
-            sb.append( format( tps ) );
-            sb.append( ", " );
+        // Paper start - Further improve tick handling
+        double[] tps = org.bukkit.Bukkit.getTPS();
+        String[] tpsAvg = new String[tps.length];
+
+        for ( int i = 0; i < tps.length; i++) {
+            tpsAvg[i] = format( tps[i] );
         }
-        sender.sendMessage( sb.substring( 0, sb.length() - 2 ) );
+        sender.sendMessage( ChatColor.GOLD + "TPS from last 1m, 5m, 15m: " + org.apache.commons.lang.StringUtils.join(tpsAvg, ", "));
+        // Paper end
 
         return true;
     }
 
-    private String format(double tps)
+    private static String format(double tps) // Paper - Made static
     {
         return ( ( tps > 18.0 ) ? ChatColor.GREEN : ( tps > 16.0 ) ? ChatColor.YELLOW : ChatColor.RED ).toString()
                 + ( ( tps > 20.0 ) ? "*" : "" ) + Math.min( Math.round( tps * 100.0 ) / 100.0, 20.0 );
-- 
2.10.2