Ports SSmobs from Virgo

- Ports SSmobs from Virgo
- Has some debugging code, that was added a long time ago

code/controllers/Processes/mob.dm

@@ -1,29 +0,0 @@
-/datum/controller/process/mob
-	var/tmp/datum/updateQueue/updateQueueInstance
-
-/datum/controller/process/mob/setup()
-	name = "mob"
-	schedule_interval = 20 // every 2 seconds
-	start_delay = 16
-
-/datum/controller/process/mob/started()
-	..()
-	if(!mob_list)
-		mob_list = list()
-
-/datum/controller/process/mob/doWork()
-	for(last_object in mob_list)
-		var/mob/M = last_object
-		if(M && !QDELETED(M))
-			try
-				M.Life()
-			catch(var/exception/e)
-				catchException(e, M)
-			SCHECK
-		else
-			catchBadType(M)
-			mob_list -= M
-
-/datum/controller/process/mob/statProcess()
-	..()
-	stat(null, "[mob_list.len] mobs")

code/controllers/subsystems/mobs.dm

@@ -0,0 +1,55 @@
+//
+// Mobs Subsystem - Process mob.Life()
+//
+
+SUBSYSTEM_DEF(mobs)
+	name = "Mobs"
+	priority = 100
+	wait = 2 SECONDS
+	flags = SS_KEEP_TIMING|SS_NO_INIT
+	runlevels = RUNLEVEL_GAME | RUNLEVEL_POSTGAME
+
+	var/list/currentrun = list()
+	var/log_extensively = FALSE
+	var/list/timelog = list()
+	var/list/busy_z_levels = list()
+	var/slept_mobs = 0
+
+/datum/controller/subsystem/mobs/stat_entry()
+	..("P: [global.mob_list.len] | S: [slept_mobs]")
+
+/datum/controller/subsystem/mobs/fire(resumed = 0)
+	var/list/busy_z_levels = src.busy_z_levels
+
+	if (!resumed)
+		slept_mobs = 0
+		src.currentrun = mob_list.Copy()
+		busy_z_levels.Cut()
+		for(var/played_mob in player_list)
+			if(!played_mob || isobserver(played_mob))
+				continue
+			var/mob/pm = played_mob
+			busy_z_levels |= pm.z
+
+	//cache for sanic speed (lists are references anyways)
+	var/list/currentrun = src.currentrun
+	var/times_fired = src.times_fired
+	while(currentrun.len)
+		var/mob/M = currentrun[currentrun.len]
+		currentrun.len--
+
+		if(QDELETED(M))
+			mob_list -= M
+		else
+			// Right now mob.Life() is unstable enough I think we need to use a try catch.
+			// Obviously we should try and get rid of this for performance reasons when we can.
+			try
+				if(M.low_priority && !(M.z in busy_z_levels))
+					slept_mobs++
+					continue
+				M.Life(times_fired)
+			catch(var/exception/e)
+				log_runtime(e, M, "Caught by [name] subsystem")
+
+		if (MC_TICK_CHECK)
+			return