Fix tick loop bug - Fixes #624

We were not calculating time after the sleep ,resulting in wrong
calculations. This caused us to go 100ms, 0ms, 100ms, 0 ms repeatedly.

Spigot-Server-Patches/0020-Further-improve-server-tick-loop.patch

@@ -1,4 +1,4 @@
-From bfa96ef58792ce8ee38410f4338d7860aa503a4b Mon Sep 17 00:00:00 2001
+From f34109ceb110e7cc63f4d4d037245a64ff5a2449 Mon Sep 17 00:00:00 2001
 From: Aikar <aikar@aikar.co>
 Date: Tue, 1 Mar 2016 23:09:29 -0600
 Subject: [PATCH] Further improve server tick loop
@@ -12,7 +12,7 @@ Previous implementation did not calculate TPS correctly.
 Switch to a realistic rolling average and factor in std deviation as an extra reporting variable
 
 diff --git a/src/main/java/net/minecraft/server/MinecraftServer.java b/src/main/java/net/minecraft/server/MinecraftServer.java
-index 7539bb215..91fb12128 100644
+index 7539bb215..4476799d8 100644
 --- a/src/main/java/net/minecraft/server/MinecraftServer.java
 +++ b/src/main/java/net/minecraft/server/MinecraftServer.java
 @@ -113,16 +113,12 @@ public abstract class MinecraftServer implements Runnable, ICommandListener, IAs
@@ -107,13 +107,12 @@ index 7539bb215..91fb12128 100644
 +                    if (wait > 0) {
 +                        if (catchupTime < 2E6) {
 +                            wait += Math.abs(catchupTime);
-+                        }
-+                        if (wait < catchupTime) {
++                        } else if (wait < catchupTime) {
 +                            catchupTime -= wait;
 +                            wait = 0;
-+                        } else if (catchupTime > 2E6) {
++                        } else {
 +                            wait -= catchupTime;
-+                            catchupTime -= catchupTime;
++                            catchupTime = 0;
 +                        }
 +                    }
                      if (wait > 0) {
@@ -122,6 +121,7 @@ index 7539bb215..91fb12128 100644
 -                        continue;
 -                    } else {
 -                        catchupTime = Math.min(1000000000, Math.abs(wait));
++                        curTime = System.nanoTime();
 +                        wait = TICK_TIME - (curTime - lastTick);
                      }
  
@@ -210,5 +210,5 @@ index be2e31dea..6d21c3269 100644
          return ( ( tps > 18.0 ) ? ChatColor.GREEN : ( tps > 16.0 ) ? ChatColor.YELLOW : ChatColor.RED ).toString()
                  + ( ( tps > 20.0 ) ? "*" : "" ) + Math.min( Math.round( tps * 100.0 ) / 100.0, 20.0 );
 -- 
-2.11.0.windows.3
+2.11.0