new: smoothChunkSendingRate

Author: ishland

c2me-notickvd/src/main/java/com/ishland/c2me/notickvd/MixinPlugin.java

@@ -13,6 +13,10 @@ public boolean shouldApplyMixin(String targetClassName, String mixinClassName) {
             return Config.enableExtRenderDistanceProtocol;
         }
 
+        if (mixinClassName.startsWith("com.ishland.c2me.notickvd.mixin.smooth_sending_rate.")) {
+            return Config.smoothChunkSendingRate;
+        }
+
         return true;
     }
 }

c2me-notickvd/src/main/java/com/ishland/c2me/notickvd/common/Config.java

@@ -23,6 +23,17 @@ Requires Fabric API (currently %s)
                     """.formatted(C2MEConstants.EXT_RENDER_DISTANCE_ID, ModStatuses.fabric_networking_api_v1 ? "available" : "unavailable"))
             .getBoolean(true, false);
 
+    public static final boolean smoothChunkSendingRate = new ConfigSystem.ConfigAccessor()
+            .key("noTickViewDistance.smoothChunkSendingRate")
+            .comment("""
+                    Whether to attempt to smooth out chunk sending rate
+                    
+                    Due to the nature of chunk loading and generation, chunks reach full status in bursts,
+                    which can cause frame time stability if the server also delivers chunks in a bursty way
+                    This config attempts to smooth out the bursty stream of chunks to help frame time stability
+                    """)
+            .getBoolean(true, false);
+
     public static final boolean ensureChunkCorrectness = new ConfigSystem.ConfigAccessor()
             .key("noTickViewDistance.ensureChunkCorrectness")
             .comment("Whether to ensure correct chunks within normal render distance \n" +

c2me-notickvd/src/main/java/com/ishland/c2me/notickvd/common/smooth_sending_rate/ExponentialMovingAverage.java

@@ -0,0 +1,27 @@
+package com.ishland.c2me.notickvd.common.smooth_sending_rate;
+
+// Taken from the Linux kernel loadavg
+public class ExponentialMovingAverage {
+    private final double expRise;
+    private final double expFall;
+    private double oldValue = 0;
+
+    public ExponentialMovingAverage(double tickSeconds, double tauRiseSeconds, double tauFallSeconds) {
+        this.expRise = 1.0 / Math.exp(tickSeconds / tauRiseSeconds);
+        this.expFall = 1.0 / Math.exp(tickSeconds / tauFallSeconds);
+    }
+
+    public double onTick(double value) {
+        double newValue =
+                value > this.oldValue
+                ? this.oldValue * this.expRise + value * (1.0 - this.expRise)
+                : this.oldValue * this.expFall + value * (1.0 - this.expFall);
+        this.oldValue = newValue;
+        return newValue;
+    }
+
+    public double getCurrent() {
+        return this.oldValue;
+    }
+
+}

c2me-notickvd/src/main/java/com/ishland/c2me/notickvd/mixin/smooth_sending_rate/MixinChunkDataSender.java

@@ -0,0 +1,79 @@
+package com.ishland.c2me.notickvd.mixin.smooth_sending_rate;
+
+import com.ishland.c2me.notickvd.common.smooth_sending_rate.ExponentialMovingAverage;
+import com.llamalad7.mixinextras.injector.ModifyReturnValue;
+import it.unimi.dsi.fastutil.longs.LongSet;
+import net.minecraft.server.network.ChunkDataSender;
+import net.minecraft.server.network.ServerPlayerEntity;
+import net.minecraft.text.Text;
+import net.minecraft.world.chunk.WorldChunk;
+import org.objectweb.asm.Opcodes;
+import org.spongepowered.asm.mixin.Final;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.Shadow;
+import org.spongepowered.asm.mixin.Unique;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Inject;
+import org.spongepowered.asm.mixin.injection.Redirect;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfo;
+
+import java.util.List;
+
+@Mixin(ChunkDataSender.class)
+public class MixinChunkDataSender {
+
+    @Shadow
+    @Final
+    private LongSet chunks;
+
+    @Shadow
+    private float pending;
+    @Shadow
+    @Final
+    private boolean local;
+    @Shadow
+    private float desiredBatchSize;
+    @Unique
+    private ExponentialMovingAverage c2me$ema;
+    @Unique
+    private ExponentialMovingAverage c2me$emaActual;
+    @Unique
+    private int c2me$lastTickSent = 0;
+
+    @Inject(method = "<init>", at = @At(value = "RETURN"))
+    private void onInit(boolean local, CallbackInfo ci) {
+        this.c2me$ema = new ExponentialMovingAverage(1.0 / 20.0, 10.0, 4.0);
+        this.c2me$emaActual = new ExponentialMovingAverage(1.0 / 20.0, 0.1, 0.1);
+    }
+
+    @Inject(method = "sendChunkBatches", at = @At(value = "HEAD"))
+    private void onTick(ServerPlayerEntity player, CallbackInfo ci) {
+        this.c2me$ema.onTick(this.chunks.size());
+        this.c2me$emaActual.onTick(this.c2me$lastTickSent);
+//        player.sendMessage(Text.of(String.format("Current target sending rate: %.1f cps, %.1f cps, actual: %.1f cps", this.c2me$getTargetSendingRate() * 20.0, this.desiredBatchSize * 20.0, this.c2me$emaActual.getCurrent() * 20.0)), true);
+        this.c2me$lastTickSent = 0;
+    }
+
+    @Redirect(method = "sendChunkBatches", at = @At(value = "FIELD", target = "Lnet/minecraft/server/network/ChunkDataSender;desiredBatchSize:F", opcode = Opcodes.GETFIELD), require = 2)
+    private float redirectDesiredBatchSize(ChunkDataSender instance) {
+        assert instance == (Object) this;
+        return this.local ? (float) this.c2me$getTargetSendingRate() : Math.min(this.desiredBatchSize, (float) this.c2me$getTargetSendingRate());
+    }
+
+    @Redirect(method = "makeBatch", at = @At(value = "FIELD", target = "Lnet/minecraft/server/network/ChunkDataSender;local:Z", opcode = Opcodes.GETFIELD))
+    private boolean applyClampingToLocal(ChunkDataSender instance) {
+        return false;
+    }
+
+    @ModifyReturnValue(method = "makeBatch", at = @At("RETURN"))
+    private List<WorldChunk> onBatch(List<WorldChunk> original) {
+        this.c2me$lastTickSent = original.size();
+        return original;
+    }
+
+    @Unique
+    private double c2me$getTargetSendingRate() {
+        return (this.c2me$ema.getCurrent()) / 10.0F;
+    }
+
+}

c2me-notickvd/src/main/resources/c2me-notickvd.mixins.json

@@ -17,7 +17,8 @@
     "MixinWorld",
     "MixinWorldChunk",
     "ext_render_distance.MixinServerConfigurationNetworkHandler",
-    "ext_render_distance.MixinServerPlayNetworkHandler"
+    "ext_render_distance.MixinServerPlayNetworkHandler",
+    "smooth_sending_rate.MixinChunkDataSender"
   ],
   "client": [
     "client.MixinIntegratedServer"