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89d51d5f29
Because this exploit has been widely known for years and has not been fixed by Mojang, we decided that it was worth allowing people to toggle it on/off due to how easy it is to make it configurable. It should be noted that this decision does not promise all future exploits will be configurable.
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 cd812f3fe362de5ddc414862dedab2e9727ca776..2bc69e84b4e2ba8f816322d649e42570ab9242e5 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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@@ -30,8 +30,10 @@ public class DataFixerBuilder {
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private final Int2ObjectSortedMap<Schema> schemas = new Int2ObjectAVLTreeMap<>();
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private final List<DataFix> globalList = Lists.newArrayList();
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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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@@ -78,6 +80,7 @@ public class DataFixerBuilder {
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final IntBidirectionalIterator 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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