papermc/Spigot-Server-Patches/0040-Further-improve-server-tick-loop.patch

From c6bcae3d4cf7234371b1a75dceba995b8a82713f Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Sun, 19 Oct 2014 15:56:39 -0500
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 fa10ea1..953a88c 100644
--- a/src/main/java/net/minecraft/server/MinecraftServer.java
+++ b/src/main/java/net/minecraft/server/MinecraftServer.java
@@ -102,17 +102,11 @@ public abstract class MinecraftServer implements ICommandListener, Runnable, IMo
     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) { // CraftBukkit - signature file -> OptionSet
         net.minecraft.util.io.netty.util.ResourceLeakDetector.setEnabled( false ); // Spigot - disable
@@ -446,12 +440,53 @@ public abstract class MinecraftServer implements ICommandListener, Runnable, IMo
         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 {
@@ -464,26 +499,45 @@ public abstract class MinecraftServer implements ICommandListener, Runnable, IMo
                 this.a(this.q);
 
                 // 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);
+                    // Paperspigot end
+
+                    if ( ++MinecraftServer.currentTick % SAMPLE_INTERVAL == 0 ) // PaperSpigot - Further improve tick loop
                     {
-                        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)
+                        // PaperSpigot start - Further improve tick loop
+                        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 1548042..ed5bb2e 100644
--- a/src/main/java/org/bukkit/craftbukkit/CraftServer.java
+++ b/src/main/java/org/bukkit/craftbukkit/CraftServer.java
@@ -1842,6 +1842,17 @@ public final class CraftServer implements Server {
             return org.spigotmc.SpigotConfig.config;
         }
 
+        // 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 void broadcast( BaseComponent component )
         {
diff --git a/src/main/java/org/spigotmc/TicksPerSecondCommand.java b/src/main/java/org/spigotmc/TicksPerSecondCommand.java
index 2b8343d..1780e35 100644
--- a/src/main/java/org/spigotmc/TicksPerSecondCommand.java
+++ b/src/main/java/org/spigotmc/TicksPerSecondCommand.java
@@ -1,8 +1,7 @@
 package org.spigotmc;
 
-import com.google.common.base.Joiner;
-import net.minecraft.server.MinecraftServer;
-import net.minecraft.util.com.google.common.collect.Iterables;
+import org.apache.commons.lang.StringUtils;
+import org.bukkit.Bukkit;
 import org.bukkit.ChatColor;
 import org.bukkit.command.Command;
 import org.bukkit.command.CommandSender;
@@ -26,18 +25,21 @@ 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 = 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: " + StringUtils.join(tpsAvg, ", "));
+        // PaperSpigot end
 
         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