Better server sleeping/waiting

2026-02-17 16:37:43 +01:00 · 2019-07-27 16:30:19 -05:00
parent 695f35ed3b
commit 42ca953aa3
1 changed files with 90 additions and 0 deletions
--- a/patches/server/0062-Better-server-sleeping-waiting.patch
+++ b/patches/server/0062-Better-server-sleeping-waiting.patch
@@ -0,0 +1,90 @@
+From 24153d1feb47ab075ec741ecd5934016c7cd9e9b Mon Sep 17 00:00:00 2001
+From: Spottedleaf <Spottedleaf@users.noreply.github.com>
+Date: Sat, 20 Jul 2019 15:20:04 -0700
+Subject: [PATCH] Better server sleeping/waiting
+
+---
+ .../minecraft/server/IAsyncTaskHandler.java   | 47 +++++++++++++++++++
+ .../net/minecraft/server/MinecraftServer.java |  8 ++--
+ 2 files changed, 52 insertions(+), 3 deletions(-)
+
+diff --git a/src/main/java/net/minecraft/server/IAsyncTaskHandler.java b/src/main/java/net/minecraft/server/IAsyncTaskHandler.java
+index 84024e6ba4..78ea0a251e 100644
+--- a/src/main/java/net/minecraft/server/IAsyncTaskHandler.java
+++ b/src/main/java/net/minecraft/server/IAsyncTaskHandler.java
+@@ -91,6 +91,53 @@ public abstract class IAsyncTaskHandler<R extends Runnable> implements Mailbox<R
+ 
+     }
+ 
+    // Paper start - better waiting (MC-149018)
+    public void waitFor(final long time) { // time in ns
+        final long start = System.nanoTime();
+
+        ++this.e;
+
+        try {
+            while ((System.nanoTime() - start) < time) {
+                if (this.executeNext()) {
+                    // re-check condition
+                    continue;
+                }
+
+                // no tasks to execute
+                final long timeUsed = System.nanoTime() - start;
+                final long budget = time - timeUsed;
+
+                if (budget <= 50_000L) { // 50us, this can be tuned, even to 0
+                    // this is a presumption that park does not have the precision to sleep
+                    // for under 50us and we would oversleep, although this branch is not very
+                    // neccessary for this to work
+                    break;
+                }
+
+                // In order to avoid thread scheduling potentially waking up us
+                // late we aim to wake up a millisecond early
+                final long budgetWithPreempt = budget - (int)(1.0e6);
+
+                if (budgetWithPreempt <= 0) {
+                    // we don't have a millisecond to spare
+                    LockSupport.parkNanos("short park for timed wait", 50_000L);
+                    continue;
+                }
+
+                // Optionally before entering the long park we could spinwait a bit here,
+                // alternatively, we could spinwait for longer periods instead of one park
+
+
+                LockSupport.parkNanos("long park for timed wait", budgetWithPreempt);
+                // additions to the queue will unpark us
+            }
+        } finally {
+            --this.e;
+        }
+    }
+    // Paper end
+
+     public void executeAll() { // Paper - protected -> public
+         while (this.executeNext()) {
+             ;
+diff --git a/src/main/java/net/minecraft/server/MinecraftServer.java b/src/main/java/net/minecraft/server/MinecraftServer.java
+index a8703a42e5..375bc274a7 100644
+--- a/src/main/java/net/minecraft/server/MinecraftServer.java
+++ b/src/main/java/net/minecraft/server/MinecraftServer.java
+@@ -1000,9 +1000,11 @@ public abstract class MinecraftServer extends IAsyncTaskHandlerReentrant<TickTas
+ 
+     protected void sleepForTick() {
+         //this.executeAll(); // Paper - move this into the tick method for timings
+-        this.awaitTasks(() -> {
+-            return !this.canSleepForTick();
+-        });
+        // Paper start - improve wait (MC-149018)
+        // ac will be false here given that flag is set depending on the last value of executeNext, which will be false
+        // after executing all tasks
+        this.waitFor((this.nextTick * 1000 * 1000) - System.nanoTime());
+        // Paper end
+     }
+ 
+     @Override
+-- 
+2.20.1
+