From d2787c0ed42e7c7dc65ecd1568870afa951229db Mon Sep 17 00:00:00 2001
From: md_5 <md_5@live.com.au>
Date: Sun, 3 Feb 2013 12:28:17 +1100
Subject: [PATCH] Tick loop optimization - sleep for as long as possible.

---
 .../java/net/minecraft/server/MinecraftServer.java | 50 +++++++++-------------
 .../craftbukkit/command/TicksPerSecondCommand.java | 35 +++++++++++++++
 2 files changed, 55 insertions(+), 30 deletions(-)
 create mode 100644 src/main/java/org/bukkit/craftbukkit/command/TicksPerSecondCommand.java

diff --git a/src/main/java/net/minecraft/server/MinecraftServer.java b/src/main/java/net/minecraft/server/MinecraftServer.java
index 955a3ac..99a6cf4 100644
--- a/src/main/java/net/minecraft/server/MinecraftServer.java
+++ b/src/main/java/net/minecraft/server/MinecraftServer.java
@@ -86,6 +86,12 @@ public abstract class MinecraftServer implements ICommandListener, Runnable, IMo
     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;
+    public static double currentTPS = 0;
+    private static long catchupTime = 0;
+    // Spigot end
 
     public MinecraftServer(OptionSet options) { // CraftBukkit - signature file -> OptionSet
         l = this;
@@ -397,39 +403,23 @@ public abstract class MinecraftServer implements ICommandListener, Runnable, IMo
     public void run() {
         try {
             if (this.init()) {
-                long i = System.currentTimeMillis();
-
-                for (long j = 0L; this.isRunning; this.Q = true) {
-                    long k = System.currentTimeMillis();
-                    long l = k - i;
-
-                    if (l > 2000L && i - this.R >= 15000L) {
-                        if (this.server.getWarnOnOverload()) // CraftBukkit - Added option to suppress warning messages
-                        log.warning("Can\'t keep up! Did the system time change, or is the server overloaded?");
-                        l = 2000L;
-                        this.R = i;
-                    }
-
-                    if (l < 0L) {
-                        log.warning("Time ran backwards! Did the system time change?");
-                        l = 0L;
-                    }
-
-                    j += l;
-                    i = k;
-                    if (this.worlds.get(0).everyoneDeeplySleeping()) { // CraftBukkit
-                        this.q();
-                        j = 0L;
+                // Spigot start
+                for (long lastTick = 0L; this.isRunning; this.Q = true) {
+                    long curTime = System.nanoTime();
+                    long wait = TICK_TIME - (curTime - lastTick) - catchupTime;
+                    if (wait > 0) {
+                        Thread.sleep(wait / 1000000);
+                        catchupTime = 0;
+                        continue;
                     } else {
-                        while (j > 50L) {
-                            MinecraftServer.currentTick = (int) (System.currentTimeMillis() / 50); // CraftBukkit
-                            j -= 50L;
-                            this.q();
-                        }
+                        catchupTime = Math.min(TICK_TIME * TPS, Math.abs(wait));
                     }
-
-                    Thread.sleep(1L);
+                    currentTPS = (currentTPS * 0.95) + (1E9 / (curTime - lastTick) * 0.05);
+                    lastTick = curTime;
+                    MinecraftServer.currentTick++;
+                    this.q();
                 }
+                // Spigot end
             } else {
                 this.a((CrashReport) null);
             }
diff --git a/src/main/java/org/bukkit/craftbukkit/command/TicksPerSecondCommand.java b/src/main/java/org/bukkit/craftbukkit/command/TicksPerSecondCommand.java
new file mode 100644
index 0000000..f114a31
--- /dev/null
+++ b/src/main/java/org/bukkit/craftbukkit/command/TicksPerSecondCommand.java
@@ -0,0 +1,35 @@
+package org.bukkit.craftbukkit.command;
+
+import net.minecraft.server.MinecraftServer;
+import org.bukkit.ChatColor;
+import org.bukkit.command.Command;
+import org.bukkit.command.CommandSender;
+
+public class TicksPerSecondCommand extends Command {
+
+    public TicksPerSecondCommand(String name) {
+        super(name);
+        this.description = "Gets the current ticks per second for the server";
+        this.usageMessage = "/tps";
+        this.setPermission("bukkit.command.tps");
+    }
+
+    @Override
+    public boolean execute(CommandSender sender, String currentAlias, String[] args) {
+        if (!testPermission(sender)) return true;
+
+        double tps = Math.min(20,  Math.round(MinecraftServer.currentTPS * 10) / 10.0);
+        ChatColor color;
+        if (tps > 19.2D) {
+            color = ChatColor.GREEN;
+        } else if (tps > 17.4D) {
+            color = ChatColor.YELLOW;
+        } else {
+            color = ChatColor.RED;
+        }
+
+        sender.sendMessage(ChatColor.GOLD + "[TPS] " + color + tps);
+
+        return true;
+    }
+}
-- 
1.8.1-rc2