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Mirror von https://github.com/PaperMC/Paper.git synchronisiert 2024-12-15 11:00:06 +01:00
Paper/patches/server/0409-Cache-DataFixerUpper-Rewrite-Rules-on-demand.patch
Bjarne Koll c5a10665b8
Remove wall-time / unused skip tick protection (#11412)
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.
2024-09-19 16:36:07 +02:00

55 Zeilen
2.9 KiB
Diff

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Sat, 12 Sep 2020 17:21:38 -0400
Subject: [PATCH] Cache DataFixerUpper Rewrite Rules on demand
Mojang precaches every single potential rewrite rule that could ever
exist on server startup. This includes rules from all the way back to versions from 6+ years ago.
This is the source of why the server hogs every CPU core at 100% every start.
For anyone who hard resets for updates or has force upgraded their entire world, this
results in completely wasted cpu cycles.
This massive CPU usage also delays server startup time.
We improve this by making "min version to precache" that defaults to a future version
so that no rewrite rules are precached.
someone who expects to be converting a lot chunks could theoretically set
-DPaper.minPrecachedDatafixVersion=<dataVersionConvertingFrom> as a startup
parameter and only build from that point on.
However this will likely never be needed as the server will still run
the same cache logic on demand when it's actually needed. The only
cost would be some delay on the FIRST chunk conversion, but paper already
runs chunk conversions on another thread so this will likely never be
a concern for TPS.
This patch will significantly reduce CPU use on startup, reduce memory usage,
and improve server startup time.
diff --git a/src/main/java/com/mojang/datafixers/DataFixerBuilder.java b/src/main/java/com/mojang/datafixers/DataFixerBuilder.java
index 4232ce05ad7dd122a78a04ccef3b59d4caf542df..2cce259c738de2680e219d30dc3020458f4442d6 100644
--- a/src/main/java/com/mojang/datafixers/DataFixerBuilder.java
+++ b/src/main/java/com/mojang/datafixers/DataFixerBuilder.java
@@ -29,8 +29,10 @@ public class DataFixerBuilder {
private final Int2ObjectSortedMap<Schema> schemas = new Int2ObjectAVLTreeMap<>();
private final List<DataFix> globalList = new ArrayList<>();
private final IntSortedSet fixerVersions = new IntAVLTreeSet();
+ private final int minDataFixPrecacheVersion; // Paper - Perf: Cache DataFixerUpper Rewrite Rules on demand
public DataFixerBuilder(final int dataVersion) {
+ minDataFixPrecacheVersion = Integer.getInteger("Paper.minPrecachedDatafixVersion", dataVersion+1) * 10; // Paper - Perf: default to precache nothing - mojang stores versions * 10 to allow for 'sub versions'
this.dataVersion = dataVersion;
}
@@ -88,6 +90,7 @@ public class DataFixerBuilder {
final IntIterator iterator = fixerUpper.fixerVersions().iterator();
while (iterator.hasNext()) {
final int versionKey = iterator.nextInt();
+ if (versionKey < minDataFixPrecacheVersion) continue; // Paper - Perf: Cache DataFixerUpper Rewrite Rules on demand
final Schema schema = schemas.get(versionKey);
for (final String typeName : schema.types()) {
if (!requiredTypeNames.contains(typeName)) {