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c5a10665b8
Spigot still maintains some partial implementation of "tick skipping", a practice in which the MinecraftServer.currentTick field is updated not by an increment of one per actual tick, but instead set to System.currentTimeMillis() / 50. This behaviour means that the tracked tick may "skip" a tick value in case a previous tick took more than the expected 50ms. To compensate for this in important paths, spigot/craftbukkit implements "wall-time". Instead of incrementing/decrementing ticks on block entities/entities by one for each call to their tick() method, they instead increment/decrement important values, like an ItemEntity's age or pickupDelay, by the difference of `currentTick - lastTick`, where `lastTick` is the value of `currentTick` during the last tick() call. These "fixes" however do not play nicely with minecraft's simulation distance as entities/block entities implementing the above behaviour would "catch up" their values when moving from a non-ticking chunk to a ticking one as their `lastTick` value remains stuck on the last tick in a ticking chunk and hence lead to a large "catch up" once ticked again. Paper completely removes the "tick skipping" behaviour (See patch "Further-improve-server-tick-loop"), making the above precautions completely unnecessary, which also rids paper of the previous described incompatibility with non-ticking chunks.
91 lines
4.2 KiB
Diff
91 lines
4.2 KiB
Diff
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Aikar <aikar@aikar.co>
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Date: Fri, 29 May 2020 20:29:02 -0400
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Subject: [PATCH] Synchronize PalettedContainer instead of
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ThreadingDetector/Semaphore
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Mojang has flaws in their logic about chunks being concurrently
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wrote to. So we constantly see crashes around multiple threads writing.
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Additionally, java has optimized synchronization so well that its
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in many times faster than trying to manage read write locks for low
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contention situations.
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And this is extremely a low contention situation.
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diff --git a/src/main/java/net/minecraft/world/level/chunk/PalettedContainer.java b/src/main/java/net/minecraft/world/level/chunk/PalettedContainer.java
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index 2e5afbd2a69c4eeabd9a48bff6a37a7004565716..2fa0097a9374a89177e4f1068d1bfed30b8ff122 100644
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--- a/src/main/java/net/minecraft/world/level/chunk/PalettedContainer.java
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+++ b/src/main/java/net/minecraft/world/level/chunk/PalettedContainer.java
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@@ -30,14 +30,14 @@ public class PalettedContainer<T> implements PaletteResize<T>, PalettedContainer
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public final IdMap<T> registry;
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private volatile PalettedContainer.Data<T> data;
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private final PalettedContainer.Strategy strategy;
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- private final ThreadingDetector threadingDetector = new ThreadingDetector("PalettedContainer");
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+ // private final ThreadingDetector threadingDetector = new ThreadingDetector("PalettedContainer"); // Paper - unused
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public void acquire() {
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- this.threadingDetector.checkAndLock();
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+ // this.threadingDetector.checkAndLock(); // Paper - disable this - use proper synchronization
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}
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public void release() {
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- this.threadingDetector.checkAndUnlock();
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+ // this.threadingDetector.checkAndUnlock(); // Paper - disable this
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}
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public static <T> Codec<PalettedContainer<T>> codecRW(IdMap<T> idList, Codec<T> entryCodec, PalettedContainer.Strategy paletteProvider, T defaultValue) {
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@@ -104,7 +104,7 @@ public class PalettedContainer<T> implements PaletteResize<T>, PalettedContainer
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}
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@Override
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- public int onResize(int newBits, T object) {
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+ public synchronized int onResize(int newBits, T object) { // Paper - synchronize
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PalettedContainer.Data<T> data = this.data;
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PalettedContainer.Data<T> data2 = this.createOrReuseData(data, newBits);
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data2.copyFrom(data.palette, data.storage);
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@@ -129,7 +129,7 @@ public class PalettedContainer<T> implements PaletteResize<T>, PalettedContainer
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return this.getAndSet(this.strategy.getIndex(x, y, z), value);
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}
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- private T getAndSet(int index, T value) {
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+ private synchronized T getAndSet(int index, T value) { // Paper - synchronize
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int i = this.data.palette.idFor(value);
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int j = this.data.storage.getAndSet(index, i);
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return this.data.palette.valueFor(j);
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@@ -145,7 +145,7 @@ public class PalettedContainer<T> implements PaletteResize<T>, PalettedContainer
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}
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}
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- private void set(int index, T value) {
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+ private synchronized void set(int index, T value) { // Paper - synchronize
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int i = this.data.palette.idFor(value);
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this.data.storage.set(index, i);
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}
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@@ -168,7 +168,7 @@ public class PalettedContainer<T> implements PaletteResize<T>, PalettedContainer
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intSet.forEach(id -> action.accept(palette.valueFor(id)));
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}
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- public void read(FriendlyByteBuf buf) {
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+ public synchronized void read(FriendlyByteBuf buf) { // Paper - synchronize
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this.acquire();
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try {
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@@ -183,7 +183,7 @@ public class PalettedContainer<T> implements PaletteResize<T>, PalettedContainer
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}
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@Override
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- public void write(FriendlyByteBuf buf) {
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+ public synchronized void write(FriendlyByteBuf buf) { // Paper - synchronize
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this.acquire();
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try {
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@@ -231,7 +231,7 @@ public class PalettedContainer<T> implements PaletteResize<T>, PalettedContainer
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}
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@Override
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- public PalettedContainerRO.PackedData<T> pack(IdMap<T> idList, PalettedContainer.Strategy paletteProvider) {
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+ public synchronized PalettedContainerRO.PackedData<T> pack(IdMap<T> idList, PalettedContainer.Strategy paletteProvider) { // Paper - synchronize
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this.acquire();
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PalettedContainerRO.PackedData var12;
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