Paper/Spigot-Server-Patches/0033-Further-improve-server-tick-loop.patch

From 0a8abf013236bcecd16ad30c61c62d4f9aa85dfd Mon Sep 17 00:00:00 2001
From: Zach Brown <Zbob750@live.com>
Date: Fri, 28 Nov 2014 12:48:26 -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 bdaf6fb..189fe12 100644
--- a/src/main/java/net/minecraft/server/MinecraftServer.java
+++ b/src/main/java/net/minecraft/server/MinecraftServer.java
@@ -113,17 +113,11 @@ public abstract class MinecraftServer implements ICommandListener, Runnable, 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; // PaperSpigot - 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, File file1) {
         io.netty.util.ResourceLeakDetector.setEnabled( false ); // Spigot - disable
@@ -484,12 +478,53 @@ public abstract class MinecraftServer implements ICommandListener, Runnable, IAs
         this.isRunning = false;
     }
 
-    // Spigot Start
-    private static double calcTps(double avg, double exp, double tps)
-    {
-        return ( avg * exp ) + ( tps * ( 1 - exp ) );
+    // PaperSpigot start - Further improve 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 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
+    // PaperSpigot End
  
     public void run() {
         try {
@@ -502,26 +537,43 @@ public abstract class MinecraftServer implements ICommandListener, Runnable, IAs
                 this.a(this.r);
 
                 // Spigot start
-                Arrays.fill( recentTps, 20 );
-                long lastTick = System.nanoTime(), catchupTime = 0, curTime, wait, tickSection = lastTick;
+                // PaperSpigot start - Further improve tick loop
+                //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;
+                // PaperSpigot end
                 while (this.isRunning) {
                     curTime = System.nanoTime();
-                    wait = TICK_TIME - (curTime - lastTick) - catchupTime;
+                    // PaperSpigot start - Further improve 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);
                         tickSection = curTime;
+                        // PaperSpigot end
                     }
                     lastTick = curTime;
 
diff --git a/src/main/java/org/bukkit/craftbukkit/CraftServer.java b/src/main/java/org/bukkit/craftbukkit/CraftServer.java
index 239cbd7..dca6f17 100644
--- a/src/main/java/org/bukkit/craftbukkit/CraftServer.java
+++ b/src/main/java/org/bukkit/craftbukkit/CraftServer.java
@@ -1681,6 +1681,17 @@ public final class CraftServer implements Server {
     private final Spigot spigot = new Spigot()
     {
 
+        // PaperSpigot start - Add getTPS (Further improve tick loop)
+        @Override
+        public double[] getTPS() {
+            return new double[] {
+                    MinecraftServer.getServer().tps1.getAverage(),
+                    MinecraftServer.getServer().tps5.getAverage(),
+                    MinecraftServer.getServer().tps15.getAverage()
+            };
+        }
+        // PaperSpigot end
+
         @Override
         public YamlConfiguration getConfig()
         {
diff --git a/src/main/java/org/spigotmc/TicksPerSecondCommand.java b/src/main/java/org/spigotmc/TicksPerSecondCommand.java
index be2e31d..21fd7ef 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 +23,19 @@ 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( ", " );
+        // PaperSpigot start - Further improve tick handling
+        double[] tps = org.bukkit.Bukkit.spigot().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, ", "));
 
         return true;
     }
 
-    private String format(double tps)
+    private static String format(double tps) // PaperSpigot - 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 );
-- 
1.9.1