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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.
57 lines
3.3 KiB
Diff
57 lines
3.3 KiB
Diff
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: stonar96 <minecraft.stonar96@gmail.com>
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Date: Sun, 17 Jan 2021 01:11:36 +0100
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Subject: [PATCH] Optimize HashMapPalette
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HashMapPalette uses an instance of CrudeIncrementalIntIdentityHashBiMap
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internally. A Palette has a preset maximum size = 1 << bits.
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CrudeIncrementalIntIdentityHashBiMap has an initial size but is
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automatically resized. The CrudeIncrementalIntIdentityHashBiMap is created
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with the maximum size in the constructor of HashMapPalette, with the aim
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that it doesn't need to be resized anymore. However, there are two things
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that I think Mojang hasn't considered here:
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1) The CrudeIncrementalIntIdentityHashBiMap is resized, when its initial
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size is reached and not the next time, when a further object is added.
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2) HashMapPalette adds objects (unnecessarily) before checking if the
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initial size of CrudeIncrementalIntIdentityHashBiMap is reached.
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This means to actually avoid resize operations in
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CrudeIncrementalIntIdentityHashBiMap, one has to add 2 to the initial size
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or add 1 and check the size before adding objects. This commit implements
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the second approach. Note that this isn't only an optimization but also
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makes async reads of Palettes fail-safe. An async read while the
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CrudeIncrementalIntIdentityHashBiMap is resized is fatal and can even lead
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to corrupted data. This is also something that Anti-Xray is currently
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relying on.
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diff --git a/src/main/java/net/minecraft/world/level/chunk/HashMapPalette.java b/src/main/java/net/minecraft/world/level/chunk/HashMapPalette.java
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index f80cde264393f3606bc0c54ba2fd6a467f4bcb5a..c5e1040c239874dcf20b79472bf690ee7f0a9e5f 100644
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--- a/src/main/java/net/minecraft/world/level/chunk/HashMapPalette.java
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+++ b/src/main/java/net/minecraft/world/level/chunk/HashMapPalette.java
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@@ -20,7 +20,7 @@ public class HashMapPalette<T> implements Palette<T> {
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}
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public HashMapPalette(IdMap<T> idList, int indexBits, PaletteResize<T> listener) {
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- this(idList, indexBits, listener, CrudeIncrementalIntIdentityHashBiMap.create(1 << indexBits));
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+ this(idList, indexBits, listener, CrudeIncrementalIntIdentityHashBiMap.create((1 << indexBits) + 1)); // Paper - Perf: Avoid unnecessary resize operation in CrudeIncrementalIntIdentityHashBiMap
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}
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private HashMapPalette(IdMap<T> idList, int indexBits, PaletteResize<T> listener, CrudeIncrementalIntIdentityHashBiMap<T> map) {
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@@ -38,10 +38,16 @@ public class HashMapPalette<T> implements Palette<T> {
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public int idFor(T object) {
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int i = this.values.getId(object);
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if (i == -1) {
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- i = this.values.add(object);
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- if (i >= 1 << this.bits) {
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+ // Paper start - Perf: Avoid unnecessary resize operation in CrudeIncrementalIntIdentityHashBiMap and optimize
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+ // We use size() instead of the result from add(K)
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+ // This avoids adding another object unnecessarily
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+ // Without this change, + 2 would be required in the constructor
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+ if (this.values.size() >= 1 << this.bits) {
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i = this.resizeHandler.onResize(this.bits + 1, object);
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+ } else {
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+ i = this.values.add(object);
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}
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+ // Paper end - Perf: Avoid unnecessary resize operation in CrudeIncrementalIntIdentityHashBiMap and optimize
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}
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return i;
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