Optimise mod comparison function for most common case

Author: peppy

osu.Server.Queues.ScoreStatisticsProcessor/Commands/Maintenance/MarkNonPreservedScoresCommand.cs

@@ -200,11 +200,17 @@ private static bool checkIsUserHigh(IEnumerable<SoloScore> userScores, SoloScore
 
             static bool compareMods(SoloScore a, SoloScore b)
             {
-                // Compare non-ordered mods, ignoring any settings applied.
-                var aMods = new HashSet<string>(a.ScoreData.Mods.Select(m => m.Acronym));
-                var bMods = new HashSet<string>(b.ScoreData.Mods.Select(m => m.Acronym));
+                var aMods = a.ScoreData.Mods;
+                var bMods = b.ScoreData.Mods;
 
-                return aMods.SetEquals(bMods);
+                if (aMods.Length == 0 && bMods.Length == 0)
+                    return true;
+
+                if (aMods.Length != bMods.Length)
+                    return false;
+
+                HashSet<string> bAcronyms = new HashSet<string>(bMods.Select(m => m.Acronym));
+                return aMods.All(m => bAcronyms.Contains(m.Acronym));
             }
         }
     }