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Replace LongObjectHashMap with a more efficient implementation

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After further testing it appears that while the original LongHashtable
has issues with object creation churn and is severly slower than even
java.util.HashMap in general case benchmarks it is in fact very efficient
for our use case.

With this in mind I wrote a replacement LongObjectHashMap modeled after
LongHashtable. Unlike the original implementation this one does not use
Entry objects for storage so does not have the same object creation churn.
It also uses a 2D array instead of a 3D one and does not use a cache as
benchmarking shows this is more efficient. The "bucket size" was chosen
based on benchmarking performance of the HashMap with contents that would
be plausible for a 200+ player server. This means it uses a little extra
memory for smaller servers but almost always uses less than the normal
java.util.HashMap.

To make up for the original LongHashtable being a poor choice for generic
datasets I added a mixer to the new implementation based on code from
MurmurHash. While this has no noticable effect positive or negative with
our normal use of chunk coordinates it makes the HashMap perform just as
well with nearly any kind of dataset.

After these changes ChunkProviderServer.isChunkLoaded() goes from using
20% CPU time while sampling to not even showing up after 45 minutes of
sampling due to the CPU usage being too low to be noticed.
This commit is contained in:
Travis Watkins
2012-09-11 05:51:09 -05:00
parent 9f70c1f386
commit 74b3be57b7
4 changed files with 346 additions and 457 deletions
Download Patch File Download Diff File Expand all files Collapse all files

13
src/main/java/net/minecraft/server/ChunkProviderServer.java
View File

@@ -11,6 +11,7 @@ import java.util.Set;
import java.util.Random;
import org.bukkit.Server;
import org.bukkit.craftbukkit.util.LongHash;
import org.bukkit.craftbukkit.util.LongHashSet;
import org.bukkit.craftbukkit.util.LongObjectHashMap;
import org.bukkit.event.world.ChunkUnloadEvent;
@@ -36,7 +37,7 @@ public class ChunkProviderServer implements IChunkProvider {
}
public boolean isChunkLoaded(int i, int j) {
return this.chunks.containsKey(i, j); // CraftBukkit
return this.chunks.containsKey(LongHash.toLong(i, j)); // CraftBukkit
}
public void queueUnload(int i, int j) {
@@ -50,7 +51,7 @@ public class ChunkProviderServer implements IChunkProvider {
if (k < -short1 || k > short1 || l < -short1 || l > short1 || !(this.world.keepSpawnInMemory)) { // Added 'this.world.keepSpawnInMemory'
this.unloadQueue.add(i, j);
Chunk c = this.chunks.get(i, j);
Chunk c = this.chunks.get(LongHash.toLong(i, j));
if (c != null) {
c.mustSave = true;
}
@@ -60,7 +61,7 @@ public class ChunkProviderServer implements IChunkProvider {
// CraftBukkit start
this.unloadQueue.add(i, j);
Chunk c = this.chunks.get(i, j);
Chunk c = this.chunks.get(LongHash.toLong(i, j));
if (c != null) {
c.mustSave = true;
}
@@ -81,7 +82,7 @@ public class ChunkProviderServer implements IChunkProvider {
public Chunk getChunkAt(int i, int j) {
// CraftBukkit start
this.unloadQueue.remove(i, j);
Chunk chunk = (Chunk) this.chunks.get(i, j);
Chunk chunk = (Chunk) this.chunks.get(LongHash.toLong(i, j));
boolean newChunk = false;
// CraftBukkit end
@@ -96,7 +97,7 @@ public class ChunkProviderServer implements IChunkProvider {
newChunk = true; // CraftBukkit
}
this.chunks.put(i, j, chunk); // CraftBukkit
this.chunks.put(LongHash.toLong(i, j), chunk); // CraftBukkit
if (chunk != null) {
chunk.addEntities();
}
@@ -121,7 +122,7 @@ public class ChunkProviderServer implements IChunkProvider {
public Chunk getOrCreateChunk(int i, int j) {
// CraftBukkit start
Chunk chunk = (Chunk) this.chunks.get(i, j);
Chunk chunk = (Chunk) this.chunks.get(LongHash.toLong(i, j));
chunk = chunk == null ? (!this.world.isLoading && !this.forceChunkLoad ? this.emptyChunk : this.getChunkAt(i, j)) : chunk;
if (chunk == this.emptyChunk) return chunk;