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Better server sleeping/waiting

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William Blake Galbreath
2019-07-27 16:30:19 -05:00
parent 695f35ed3b
commit 42ca953aa3
1 changed files with 90 additions and 0 deletions
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patches/server/0062-Better-server-sleeping-waiting.patch Normal file
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@@ -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