Mark large replays as requiring Server GC.

This should significantly improve loading performance of large replays.

System can be controlled by replay.server_gc_size_threshold, which defaults to 50 MiB.

This is the engine-side of https://github.com/space-wizards/SS14.Launcher/issues/177

Robust.Shared/CVars.cs

@@ -1636,6 +1636,16 @@ namespace Robust.Shared
         public static readonly CVarDef<long> ReplayMaxUncompressedSize = CVarDef.Create("replay.max_uncompressed_size",
             1024L * 1024, CVar.ARCHIVE);
 
+        /// <summary>
+        /// Size of the replay (in kilobytes) at which point the replay is considered "large",
+        /// and replay clients should enable server GC (if possible) to improve performance.
+        /// </summary>
+        /// <remarks>
+        /// Set to -1 to never make replays use server GC.
+        /// </remarks>
+        public static readonly CVarDef<long> ReplayServerGCSizeThreshold =
+            CVarDef.Create("replay.server_gc_size_threshold", 50L * 1024);
+
         /// <summary>
         /// Uncompressed size of individual files created by the replay (in kilobytes), where each file contains data
         /// for one or more ticks. Actual files may be slightly larger, this is just a threshold for the file to get

Robust.Shared/Replays/SharedReplayRecordingManager.cs

@@ -58,6 +58,7 @@ internal abstract partial class SharedReplayRecordingManager : IReplayRecordingM
     // Config variables.
     private long _maxCompressedSize;
     private long _maxUncompressedSize;
+    private long _serverGCSizeThreshold;
     private int _tickBatchSize;
     private bool _enabled;
 
@@ -71,6 +72,7 @@ internal abstract partial class SharedReplayRecordingManager : IReplayRecordingM
 
         NetConf.OnValueChanged(CVars.ReplayMaxCompressedSize, (v) => _maxCompressedSize = SaturatingMultiplyKb(v), true);
         NetConf.OnValueChanged(CVars.ReplayMaxUncompressedSize, (v) => _maxUncompressedSize = SaturatingMultiplyKb(v), true);
+        NetConf.OnValueChanged(CVars.ReplayServerGCSizeThreshold, (v) => _serverGCSizeThreshold = SaturatingMultiplyKb(v), true);
         NetConf.OnValueChanged(CVars.ReplayTickBatchSize, (v) => _tickBatchSize = Math.Min(v, MaxTickBatchSize) * 1024, true);
         NetConf.OnValueChanged(CVars.NetPvsCompressLevel, OnCompressionChanged);
     }
@@ -238,7 +240,6 @@ internal abstract partial class SharedReplayRecordingManager : IReplayRecordingM
 
         try
         {
-            WriteContentBundleInfo(_recState);
             WriteInitialMetadata(name, _recState);
         }
         catch
@@ -391,6 +392,7 @@ internal abstract partial class SharedReplayRecordingManager : IReplayRecordingM
         // this just overwrites the previous yml with additional data.
         var document = new YamlDocument(yamlMetadata.ToYaml());
         WriteYaml(recState, ReplayZipFolder / FileMetaFinal, document);
+        WriteContentBundleInfo(recState);
 
         UpdateWriteTasks();
         Reset();
@@ -412,6 +414,7 @@ internal abstract partial class SharedReplayRecordingManager : IReplayRecordingM
 
         var document = new JsonObject
         {
+            ["server_gc"] = ShouldEnableServerGC(recState),
             ["engine_version"] = info.EngineVersion,
             ["base_build"] = new JsonObject
             {
@@ -429,6 +432,14 @@ internal abstract partial class SharedReplayRecordingManager : IReplayRecordingM
         WriteBytes(recState, new ResPath("rt_content_bundle.json"), bytes);
     }
 
+    private bool ShouldEnableServerGC(RecordingState recState)
+    {
+        if (_serverGCSizeThreshold < 0)
+            return false;
+
+        return recState.CompressedSize >= _serverGCSizeThreshold;
+    }
+
     /// <summary>
     /// Get information describing the server build.
     /// This will be embedded in replay content bundles to allow the launcher to directly load them.