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Paper/Spigot-Server-Patches/0021-Further-improve-server-tick-loop.patch
Aikar 3aaba8c301
Use BigDecimal to improve accracy of TPS results - long live 20 TPS! 
It's always been commonly said to 'ignore' that TPS was '19.X', that
it was fine.

I suspect that the inaccuracy of floating point math resulted in us
losing precision over time, making it difficult to actually get back to 20,
as you know the fun 0.1 + 0.1 ... 9 more times != 1 problem.

BigDecimal supports working with doubles with higher precision.

This change makes it so our RollingAverage class maintains all of the data
using BigDecimal and using BigDecimal arithematic operations.

This ensures we have extremely high precision, enabling us to
actually be able print '20 TPS' when TPS is perfect.
2018-09-17 22:32:37 -04:00

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From c72a223551fa640d606dc0281553972891d52411 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 788f0519a8..d6ea4ae532 100644
--- a/src/main/java/net/minecraft/server/MinecraftServer.java
+++ b/src/main/java/net/minecraft/server/MinecraftServer.java
@@ -146,7 +146,7 @@ public abstract class MinecraftServer implements IAsyncTaskHandler, IMojangStati
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;
@@ -156,7 +156,7 @@ public abstract class MinecraftServer implements IAsyncTaskHandler, IMojangStati
// Spigot start
public static final int TPS = 20;
public static final int TICK_TIME = 1000000000 / TPS;
- private static final int SAMPLE_INTERVAL = 100;
+ private static final int SAMPLE_INTERVAL = 20; // Paper
public final double[] recentTps = new double[ 3 ];
public final SlackActivityAccountant slackActivityAccountant = new SlackActivityAccountant();
// Spigot end
@@ -689,7 +689,7 @@ public abstract class MinecraftServer implements IAsyncTaskHandler, IMojangStati
}
private boolean aT() {
- return SystemUtils.b() < this.aa;
+ return System.nanoTime() - lastTick + catchupTime < TICK_TIME; // Paper - improved "are we lagging" check to match our own
}
// Spigot Start
@@ -697,6 +697,57 @@ public abstract class MinecraftServer implements IAsyncTaskHandler, IMojangStati
{
return ( avg * exp ) + ( tps * ( 1 - exp ) );
}
+
+ // Paper start - Further improve server tick loop
+ private static final long SEC_IN_NANO = 1000000000;
+ private static final long MAX_CATCHUP_BUFFER = TICK_TIME * TPS * 60L;
+ private long lastTick = 0;
+ private long catchupTime = 0;
+ 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 java.math.BigDecimal total;
+ private int index = 0;
+ private final java.math.BigDecimal[] samples;
+ private final long[] times;
+
+ RollingAverage(int size) {
+ this.size = size;
+ this.time = size * SEC_IN_NANO;
+ this.total = dec(TPS).multiply(dec(SEC_IN_NANO)).multiply(dec(size));
+ this.samples = new java.math.BigDecimal[size];
+ this.times = new long[size];
+ for (int i = 0; i < size; i++) {
+ this.samples[i] = dec(TPS);
+ this.times[i] = SEC_IN_NANO;
+ }
+ }
+
+ private static java.math.BigDecimal dec(long t) {
+ return new java.math.BigDecimal(t);
+ }
+ public void add(java.math.BigDecimal x, long t) {
+ time -= times[index];
+ total = total.subtract(samples[index].multiply(dec(times[index])));
+ samples[index] = x;
+ times[index] = t;
+ time += t;
+ total = total.add(x.multiply(dec(t)));
+ if (++index == size) {
+ index = 0;
+ }
+ }
+
+ public double getAverage() {
+ return total.divide(dec(time), 30, java.math.RoundingMode.HALF_UP).doubleValue();
+ }
+ }
+ private static final java.math.BigDecimal TPS_BASE = new java.math.BigDecimal(1E9).multiply(new java.math.BigDecimal(SAMPLE_INTERVAL));
+ // Paper End
// Spigot End
public void run() {
@@ -709,29 +760,47 @@ public abstract class MinecraftServer implements IAsyncTaskHandler, IMojangStati
// Spigot start
Arrays.fill( recentTps, 20 );
- long lastTick = System.nanoTime(), catchupTime = 0, curTime, wait, tickSection = lastTick, tickCount = 1;
+ long start = System.nanoTime(), curTime, wait, tickSection = start; // Paper - Further improve server tick loop
+ lastTick = start - TICK_TIME; // Paper
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);
+ } else if (wait < catchupTime) {
+ catchupTime -= wait;
+ wait = 0;
+ } else {
+ wait -= catchupTime;
+ catchupTime = 0;
+ }
+ }
if (wait > 0) {
Thread.sleep(wait / 1000000);
- catchupTime = 0;
- continue;
- } else {
- catchupTime = Math.min(1000000000, Math.abs(wait));
+ curTime = System.nanoTime();
+ wait = TICK_TIME - (curTime - lastTick);
}
- if ( tickCount++ % 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;
+ java.math.BigDecimal currentTps = TPS_BASE.divide(new java.math.BigDecimal(diff), 30, java.math.RoundingMode.HALF_UP);
+ 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;
- MinecraftServer.currentTick = (int) (System.currentTimeMillis() / 50); // CraftBukkit
+ //MinecraftServer.currentTick = (int) (System.currentTimeMillis() / 50); // CraftBukkit // Paper - don't overwrite current tick time
this.a(this::aT);
this.aa += 50L;
// Spigot end
diff --git a/src/main/java/org/bukkit/craftbukkit/CraftServer.java b/src/main/java/org/bukkit/craftbukkit/CraftServer.java
index 273967c2ae..756accd440 100644
--- a/src/main/java/org/bukkit/craftbukkit/CraftServer.java
+++ b/src/main/java/org/bukkit/craftbukkit/CraftServer.java
@@ -1866,6 +1866,17 @@ 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 be2e31deae..6d21c32692 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 );
--
2.19.0
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