- use a memory arena to allocate msecnodes.

These are rather small and extremely frequently allocated, so they are prime candidates for memory arena, because it not only avoids fragmentation and internal overhead due to mass allocation of small memory blocks but it also makes it a lot faster to free the memory when finishing a level.

src/p_secnodes.cpp

@@ -24,6 +24,7 @@
 #include "r_state.h"
 #include "p_maputl.h"
 #include "p_blockmap.h"
+#include "memarena.h"
 
 //=============================================================================
 // phares 3/21/98
@@ -32,6 +33,7 @@
 //=============================================================================
 
 msecnode_t *headsecnode = NULL;
+FMemArena secnodearena;
 
 //=============================================================================
 //
@@ -53,7 +55,8 @@ msecnode_t *P_GetSecnode()
 	}
 	else
 	{
-		node = (msecnode_t *)M_Malloc(sizeof(*node));
+		node = 
+		node = (msecnode_t *)secnodearena.Alloc(sizeof(*node));
 	}
 	return node;
 }

src/p_setup.cpp

@@ -3552,6 +3552,7 @@ void P_FreeLevelData ()
 	P_ClearUDMFKeys();
 }
 
+extern FMemArena secnodearena;
 extern msecnode_t *headsecnode;
 
 void P_FreeExtraLevelData()
@@ -3569,19 +3570,11 @@ void P_FreeExtraLevelData()
 		}
 		FBlockNode::FreeBlocks = NULL;
 	}
-	{
-		msecnode_t *node = headsecnode;
-
-		while (node != NULL)
-		{
-			msecnode_t *next = node->m_snext;
-			M_Free (node);
-			node = next;
-		}
-		headsecnode = NULL;
-	}
+	secnodearena.FreeAllBlocks();
+	headsecnode = nullptr;
 }
 
+
 //
 // P_SetupLevel
 //