PaperMC/Spigot-Server-Patches/0301-Optimize-Region-File-Cache.patch
Shane Freeder fb25dc17c6 Updated Upstream (Bukkit/CraftBukkit)
Upstream has released updates that appears to apply and compile correctly.
This update has not been tested by PaperMC and as with ANY update, please do your own testing

Bukkit Changes:
da08d022 SPIGOT-4700: Add PlayerFishEvent.State.REEL_IN
0cef14e4 Remove draft API from selectEntities

CraftBukkit Changes:
a46fdbc6 Remove outdated build delay.
3697519b SPIGOT-4708: Fix ExactChoice recipes neglecting material
9ead7009 SPIGOT-4677: Add minecraft.admin.command_feedback permission
c3749a23 Remove the Damage tag from items when it is 0.
f74c7b95 SPIGOT-4706: Can't interact with active item
494eef45 Mention requirement of JIRA ticket for bug fixes
51d62dec SPIGOT-4702: Exception when middle clicking certain slots
be557e69 SPIGOT-4700: Add PlayerFishEvent.State.REEL_IN
2019-04-22 22:36:14 +01:00

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Diff

From ea164536bfa0dfb4d6857ee576817bbc270be45f Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Mon, 23 Jul 2018 23:40:04 -0400
Subject: [PATCH] Optimize Region File Cache
CraftBukkit added synchronization to read and write methods. This adds
much more contention on this object for accessing region files, as
the entire read and write of NBT data is now a blocking operation.
This causes issues when something then simply needs to check if a chunk exists
on the main thread, causing a block...
However, this synchronization was unnecessary, because there is already
enough synchronization done to keep things safe
1) Obtaining a Region File: Those methods are still static synchronized.
Meaning we can safely obtain a Region File concurrently.
2) RegionFile data access: Methods reading and manipulating data from
a region file are also marked synchronized, ensuring that no 2 processes
are reading or writing data at the same time.
3) Checking a region file for chunkExists: getOffset is also synchronized
ensuring that even if a chunk is currently being written, it will be safe.
By removing these synchronizations, we reduce the locking to only
when data is being write or read.
GZIP compression and NBT Buffer creation will no longer be part of the
synchronized context, reducing lock times.
Ultimately: This brings us back to Vanilla, which has had no indication of region file loss.
diff --git a/src/main/java/net/minecraft/server/RegionFileCache.java b/src/main/java/net/minecraft/server/RegionFileCache.java
index 964996976a..d072222390 100644
--- a/src/main/java/net/minecraft/server/RegionFileCache.java
+++ b/src/main/java/net/minecraft/server/RegionFileCache.java
@@ -99,7 +99,7 @@ public class RegionFileCache {
@Nullable
// CraftBukkit start - call sites hoisted for synchronization
- public static synchronized NBTTagCompound read(File file, int i, int j) throws IOException {
+ public static NBTTagCompound read(File file, int i, int j) throws IOException { // Paper - remove synchronization
RegionFile regionfile = a(file, i, j);
DataInputStream datainputstream = regionfile.a(i & 31, j & 31);
@@ -112,7 +112,7 @@ public class RegionFileCache {
}
@Nullable
- public static synchronized void write(File file, int i, int j, NBTTagCompound nbttagcompound) throws IOException {
+ public static void write(File file, int i, int j, NBTTagCompound nbttagcompound) throws IOException {
int attempts = 0; Exception laste = null; while (attempts++ < 5) { try { // Paper
RegionFile regionfile = a(file, i, j);
@@ -138,7 +138,7 @@ public class RegionFileCache {
// Paper end
}
- public static synchronized boolean chunkExists(File file, int i, int j) {
+ public static boolean chunkExists(File file, int i, int j) { // Paper - remove synchronization
RegionFile regionfile = b(file, i, j);
return regionfile != null ? regionfile.d(i & 31, j & 31) : false;
--
2.21.0