From 8cdc425d7dd51fb338db7e56e5e78cd8026542cc Mon Sep 17 00:00:00 2001
From: embeddedt <42941056+embeddedt@users.noreply.github.com>
Date: Sun, 22 Jan 2023 18:07:48 -0500
Subject: [PATCH] Ensure the main thread does not spin when no tasks are
 available

---
 .../core/config/ModernFixEarlyConfig.java     |  2 +-
 .../SyncExecutorMixin.java                    | 30 +++++++++++++++++++
 src/main/resources/modernfix.mixins.json      |  3 +-
 3 files changed, 33 insertions(+), 2 deletions(-)
 create mode 100644 src/main/java/org/embeddedt/modernfix/mixin/perf/sync_executor_sleep/SyncExecutorMixin.java

diff --git a/src/main/java/org/embeddedt/modernfix/core/config/ModernFixEarlyConfig.java b/src/main/java/org/embeddedt/modernfix/core/config/ModernFixEarlyConfig.java
index f712387e..f8ceb873 100644
--- a/src/main/java/org/embeddedt/modernfix/core/config/ModernFixEarlyConfig.java
+++ b/src/main/java/org/embeddedt/modernfix/core/config/ModernFixEarlyConfig.java
@@ -30,7 +30,7 @@ public class ModernFixEarlyConfig {
         this.addMixinRule("perf.async_jei", true);
         this.addMixinRule("perf.thread_priorities", true);
         this.addMixinRule("perf.preload_block_classes", false);
-        this.addMixinRule("perf.defer_voxelshape_optimize", false);
+        this.addMixinRule("perf.sync_executor_sleep", true);
         this.addMixinRule("perf.parallel_blockstate_cache_rebuild", true);
         this.addMixinRule("perf.deduplicate_location", true);
         this.addMixinRule("safety", true);
diff --git a/src/main/java/org/embeddedt/modernfix/mixin/perf/sync_executor_sleep/SyncExecutorMixin.java b/src/main/java/org/embeddedt/modernfix/mixin/perf/sync_executor_sleep/SyncExecutorMixin.java
new file mode 100644
index 00000000..5d092e1d
--- /dev/null
+++ b/src/main/java/org/embeddedt/modernfix/mixin/perf/sync_executor_sleep/SyncExecutorMixin.java
@@ -0,0 +1,30 @@
+package org.embeddedt.modernfix.mixin.perf.sync_executor_sleep;
+
+import net.minecraftforge.fml.ModWorkManager;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.Overwrite;
+import org.spongepowered.asm.mixin.Shadow;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Inject;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfoReturnable;
+
+import java.util.concurrent.ConcurrentLinkedDeque;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.LockSupport;
+
+@Mixin(targets = "net/minecraftforge/fml/ModWorkManager$SyncExecutor")
+public class SyncExecutorMixin {
+    @Shadow private ConcurrentLinkedDeque<Runnable> tasks;
+    private static final long PARK_TIME = TimeUnit.MILLISECONDS.toNanos(50);
+    /**
+     * Currently FML spins in driveOne while waiting for the modloading workers. We can improve this
+     * by sleeping for 50ms at a time.
+     * @author embeddedt
+     * @reason improve CPU efficiency
+     */
+    @Inject(method = "driveOne", at = @At("HEAD"), remap = false)
+    private void sleepWhileNoTasks(CallbackInfoReturnable<Boolean> cir) {
+        if(tasks.isEmpty())
+            LockSupport.parkNanos(PARK_TIME);
+    }
+}
diff --git a/src/main/resources/modernfix.mixins.json b/src/main/resources/modernfix.mixins.json
index 3b29090d..f1b0a649 100644
--- a/src/main/resources/modernfix.mixins.json
+++ b/src/main/resources/modernfix.mixins.json
@@ -22,7 +22,8 @@
     "perf.parallel_blockstate_cache_rebuild.BlocksMixin",
     "perf.parallel_blockstate_cache_rebuild.BlockCallbacksMixin",
     "perf.parallel_blockstate_cache_rebuild.ShapeCacheMixin",
-    "perf.deduplicate_location.MixinResourceLocation"
+    "perf.deduplicate_location.MixinResourceLocation",
+    "perf.sync_executor_sleep.SyncExecutorMixin"
   ],
   "client": [
     "perf.skip_first_datapack_reload.MinecraftMixin",