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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.
54 lines
2.9 KiB
Diff
54 lines
2.9 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: Sat, 12 Sep 2020 17:21:38 -0400
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Subject: [PATCH] Cache DataFixerUpper Rewrite Rules on demand
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Mojang precaches every single potential rewrite rule that could ever
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exist on server startup. This includes rules from all the way back to versions from 6+ years ago.
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This is the source of why the server hogs every CPU core at 100% every start.
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For anyone who hard resets for updates or has force upgraded their entire world, this
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results in completely wasted cpu cycles.
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This massive CPU usage also delays server startup time.
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We improve this by making "min version to precache" that defaults to a future version
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so that no rewrite rules are precached.
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someone who expects to be converting a lot chunks could theoretically set
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-DPaper.minPrecachedDatafixVersion=<dataVersionConvertingFrom> as a startup
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parameter and only build from that point on.
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However this will likely never be needed as the server will still run
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the same cache logic on demand when it's actually needed. The only
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cost would be some delay on the FIRST chunk conversion, but paper already
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runs chunk conversions on another thread so this will likely never be
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a concern for TPS.
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This patch will significantly reduce CPU use on startup, reduce memory usage,
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and improve server startup time.
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diff --git a/src/main/java/com/mojang/datafixers/DataFixerBuilder.java b/src/main/java/com/mojang/datafixers/DataFixerBuilder.java
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index 4232ce05ad7dd122a78a04ccef3b59d4caf542df..2cce259c738de2680e219d30dc3020458f4442d6 100644
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--- a/src/main/java/com/mojang/datafixers/DataFixerBuilder.java
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+++ b/src/main/java/com/mojang/datafixers/DataFixerBuilder.java
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@@ -29,8 +29,10 @@ public class DataFixerBuilder {
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private final Int2ObjectSortedMap<Schema> schemas = new Int2ObjectAVLTreeMap<>();
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private final List<DataFix> globalList = new ArrayList<>();
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private final IntSortedSet fixerVersions = new IntAVLTreeSet();
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+ private final int minDataFixPrecacheVersion; // Paper - Perf: Cache DataFixerUpper Rewrite Rules on demand
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public DataFixerBuilder(final int dataVersion) {
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+ minDataFixPrecacheVersion = Integer.getInteger("Paper.minPrecachedDatafixVersion", dataVersion+1) * 10; // Paper - Perf: default to precache nothing - mojang stores versions * 10 to allow for 'sub versions'
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this.dataVersion = dataVersion;
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}
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@@ -88,6 +90,7 @@ public class DataFixerBuilder {
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final IntIterator iterator = fixerUpper.fixerVersions().iterator();
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while (iterator.hasNext()) {
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final int versionKey = iterator.nextInt();
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+ if (versionKey < minDataFixPrecacheVersion) continue; // Paper - Perf: Cache DataFixerUpper Rewrite Rules on demand
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final Schema schema = schemas.get(versionKey);
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for (final String typeName : schema.types()) {
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if (!requiredTypeNames.contains(typeName)) {
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