From 205a8a6479e9218dabc37ebc280ba05e1e199e50 Mon Sep 17 00:00:00 2001
From: metalgearsloth <31366439+metalgearsloth@users.noreply.github.com>
Date: Tue, 14 Jul 2026 16:48:50 +1000
Subject: [PATCH] Pool PVS entity state collections (#6752)

---
 .../GameStates/PvsSystem.GetStates.cs         | 11 +++--
 Robust.Server/GameStates/PvsSystem.Pooling.cs | 41 +++++++++++++++++++
 .../GameStates/PvsSystem.Serialize.cs         |  2 +-
 .../GameStates/PvsSystem.ToSendSet.cs         |  4 ++
 .../Replays/ReplayRecordingManager.cs         |  4 +-
 5 files changed, 55 insertions(+), 7 deletions(-)

diff --git a/Robust.Server/GameStates/PvsSystem.GetStates.cs b/Robust.Server/GameStates/PvsSystem.GetStates.cs
index 87786ceace..b2247c32c6 100644
--- a/Robust.Server/GameStates/PvsSystem.GetStates.cs
+++ b/Robust.Server/GameStates/PvsSystem.GetStates.cs
@@ -22,10 +22,10 @@ internal sealed partial class PvsSystem
     /// <returns>New entity State for the given entity.</returns>
     private EntityState GetEntityState(ICommonSession? player, EntityUid entityUid, GameTick fromTick, MetaDataComponent meta)
     {
-        var changed = new List<ComponentChange>();
+        var changed = GetComponentChangeList(meta.NetComponents.Count);
 
         bool sendCompList = meta.LastComponentRemoved > fromTick;
-        HashSet<ushort>? netComps = sendCompList ? new() : null;
+        HashSet<ushort>? netComps = sendCompList ? GetNetComponentSet() : null;
         var stateEv = new ComponentGetState(player, fromTick);
 
         foreach (var (netId, component) in meta.NetComponents)
@@ -83,10 +83,10 @@ internal sealed partial class PvsSystem
     private EntityState GetFullEntityState(ICommonSession player, EntityUid entityUid, MetaDataComponent meta)
     {
         var bus = EntityManager.EventBusInternal;
-        var changed = new List<ComponentChange>();
+        var changed = GetComponentChangeList(meta.NetComponents.Count);
         var stateEv = new ComponentGetState(player, GameTick.Zero);
 
-        HashSet<ushort> netComps = new();
+        HashSet<ushort> netComps = GetNetComponentSet();
 
         foreach (var (netId, component) in meta.NetComponents)
         {
@@ -197,6 +197,7 @@ Entity: {ToPrettyString(uid)}
 Last modified: {md.EntityLastModifiedTick}
 Metadata last modified: {md.LastModifiedTick}
 Transform last modified: {Transform(uid).LastModifiedTick}");
+                        ReturnEntityState(state);
                         continue;
                     }
 
@@ -217,6 +218,8 @@ Transform last modified: {Transform(uid).LastModifiedTick}");
                     var state = GetEntityState(session, uid, fromTick, md);
                     if (!state.Empty)
                         pvsSession.States.Add(state);
+                    else
+                        ReturnEntityState(state);
                 }
             }
         }
diff --git a/Robust.Server/GameStates/PvsSystem.Pooling.cs b/Robust.Server/GameStates/PvsSystem.Pooling.cs
index 871bd8f69a..49c5735a91 100644
--- a/Robust.Server/GameStates/PvsSystem.Pooling.cs
+++ b/Robust.Server/GameStates/PvsSystem.Pooling.cs
@@ -2,6 +2,7 @@ using System;
 using System.Collections.Generic;
 using Microsoft.Extensions.ObjectPool;
 using Robust.Shared.GameObjects;
+using Robust.Shared.GameStates;
 using Robust.Shared.Utility;
 using SharpZstd.Interop;
 
@@ -19,9 +20,15 @@ internal sealed partial class PvsSystem
     private readonly ObjectPool<List<PvsIndex>> _entDataListPool
         = new DefaultObjectPool<List<PvsIndex>>(new ListPolicy<PvsIndex>(), MaxVisPoolSize);
 
+    private readonly ObjectPool<List<ComponentChange>> _componentChangeListPool
+        = new DefaultObjectPool<List<ComponentChange>>(new ListPolicy<ComponentChange>(), MaxVisPoolSize);
+
     private readonly ObjectPool<HashSet<EntityUid>> _uidSetPool
         = new DefaultObjectPool<HashSet<EntityUid>>(new SetPolicy<EntityUid>(), MaxVisPoolSize);
 
+    private readonly ObjectPool<HashSet<ushort>> _netComponentSetPool
+        = new DefaultObjectPool<HashSet<ushort>>(new SetPolicy<ushort>(), MaxVisPoolSize);
+
     private readonly ObjectPool<PvsChunk> _chunkPool =
         new DefaultObjectPool<PvsChunk>(new PvsChunkPolicy(), 256);
 
@@ -63,4 +70,38 @@ internal sealed partial class PvsSystem
             CompressionContext.Dispose();
         }
     }
+
+    private List<ComponentChange> GetComponentChangeList(int capacity)
+    {
+        var list = _componentChangeListPool.Get();
+        list.EnsureCapacity(capacity);
+        return list;
+    }
+
+    private HashSet<ushort> GetNetComponentSet()
+    {
+        return _netComponentSetPool.Get();
+    }
+
+    private void ReturnEntityState(EntityState state)
+    {
+        if (state.ComponentChanges.Value is List<ComponentChange> changes)
+            _componentChangeListPool.Return(changes);
+
+        if (state.NetComponents is { } netComps)
+        {
+            _netComponentSetPool.Return(netComps);
+            state.NetComponents = null;
+        }
+    }
+
+    internal void ClearSessionState(PvsSession session)
+    {
+        foreach (var state in session.States)
+        {
+            ReturnEntityState(state);
+        }
+
+        session.ClearState();
+    }
 }
diff --git a/Robust.Server/GameStates/PvsSystem.Serialize.cs b/Robust.Server/GameStates/PvsSystem.Serialize.cs
index 25a72ec864..7ffb6e79ec 100644
--- a/Robust.Server/GameStates/PvsSystem.Serialize.cs
+++ b/Robust.Server/GameStates/PvsSystem.Serialize.cs
@@ -71,6 +71,6 @@ internal sealed partial class PvsSystem
             _serializer.SerializeDirect(data.StateStream, data.State);
         }
 
-        data.ClearState();
+        ClearSessionState(data);
     }
 }
diff --git a/Robust.Server/GameStates/PvsSystem.ToSendSet.cs b/Robust.Server/GameStates/PvsSystem.ToSendSet.cs
index 99e3e86b5c..00aaa7185b 100644
--- a/Robust.Server/GameStates/PvsSystem.ToSendSet.cs
+++ b/Robust.Server/GameStates/PvsSystem.ToSendSet.cs
@@ -112,6 +112,8 @@ internal sealed partial class PvsSystem
 
         if (!entState.Empty)
             session.States.Add(entState);
+        else
+            ReturnEntityState(entState);
     }
 
     /// <summary>
@@ -189,6 +191,8 @@ internal sealed partial class PvsSystem
 
         if (!entState.Empty)
             session.States.Add(entState);
+        else
+            ReturnEntityState(entState);
 
         return true;
     }
diff --git a/Robust.Server/Replays/ReplayRecordingManager.cs b/Robust.Server/Replays/ReplayRecordingManager.cs
index 47c7dc74a1..9654958929 100644
--- a/Robust.Server/Replays/ReplayRecordingManager.cs
+++ b/Robust.Server/Replays/ReplayRecordingManager.cs
@@ -47,7 +47,7 @@ internal sealed partial class ReplayRecordingManager : SharedReplayRecordingMana
 
         _pvs.ComputeSessionState(_pvsSession);
         Update(_pvsSession.State);
-        _pvsSession.ClearState();
+        _pvs.ClearSessionState(_pvsSession);
         _pvsSession.LastReceivedAck = Timing.CurTick;
     }
 
@@ -55,6 +55,6 @@ internal sealed partial class ReplayRecordingManager : SharedReplayRecordingMana
     {
         base.Reset();
         _pvsSession.LastReceivedAck = GameTick.Zero;
-        _pvsSession.ClearState();
+        _pvs.ClearSessionState(_pvsSession);
     }
 }