From cc2bcfedf14010d8efaffa705e53689b266fb009 Mon Sep 17 00:00:00 2001
From: MrJWhit <48370570+MrJWhit@users.noreply.github.com>
Date: Thu, 7 Jan 2021 22:50:03 -0500
Subject: [PATCH] Update garbage.dm

---
 code/controllers/subsystem/garbage.dm | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/code/controllers/subsystem/garbage.dm b/code/controllers/subsystem/garbage.dm
index 51d56545b6..da3bb24a2f 100644
--- a/code/controllers/subsystem/garbage.dm
+++ b/code/controllers/subsystem/garbage.dm
@@ -115,18 +115,22 @@ SUBSYSTEM_DEF(garbage)
 
 	lastlevel = level
 
-	for (var/refID in queue)
-		if (!refID)
+	//We do this rather then for(var/refID in queue) because that sort of for loop copies the whole list.
+	//Normally this isn't expensive, but the gc queue can grow to 40k items, and that gets costly/causes overrun.
+	for (var/i in 1 to length(queue))
+		var/list/L = queue[i]
+		if (length(L) < 2)
 			count++
 			if (MC_TICK_CHECK)
 				return
 			continue
 
-		var/GCd_at_time = queue[refID]
+		var/GCd_at_time = L[1]
 		if(GCd_at_time > cut_off_time)
 			break // Everything else is newer, skip them
 		count++
 
+		var/refID = L[2]
 		var/datum/D
 		D = locate(refID)
 
@@ -202,10 +206,7 @@ SUBSYSTEM_DEF(garbage)
 
 	D.gc_destroyed = gctime
 	var/list/queue = queues[level]
-	if (queue[refid])
-		queue -= refid // Removing any previous references that were GC'd so that the current object will be at the end of the list.
-
-	queue[refid] = gctime
+	queue[++queue.len] = list(gctime, refid) // not += for byond reasons
 
 #ifdef LEGACY_REFERENCE_TRACKING
 /datum/controller/subsystem/garbage/proc/add_type_to_findref(type)