PeiCore AllocatePages check free pages first

MdeModulePkg/Core/Pei/Memory/MemoryServices.c

@@ -809,6 +809,20 @@ PeiAllocatePages (
     }
   }
 
+  if (!PrivateData->PeiMemoryInstalled && (PrivateData->FreeMemorySearchHintCount != 0)) {
+    // Reuse temporary-memory pages before consuming the limited free-memory top.
+    Status = FindFreeMemoryFromMemoryAllocationHob (
+               (CONST EFI_PEI_SERVICES **)PeiServices,
+               MemoryType,
+               ALIGN_VALUE (Pages, EFI_SIZE_TO_PAGES (Granularity)),
+               Granularity,
+               Memory
+               );
+    if (!EFI_ERROR (Status)) {
+      return Status;
+    }
+  }
+
   //
   // We will attempt up to two times here.
   // If we don't have memory bins, we will only attempt to allocate from the PHIT.
@@ -849,6 +863,9 @@ PeiAllocatePages (
         Padding & ~(UINTN)EFI_PAGE_MASK,
         EfiConventionalMemory
         );
+      if (!PrivateData->PeiMemoryInstalled && (PrivateData->FreeMemorySearchHintCount < MAX_UINTN)) {
+        PrivateData->FreeMemorySearchHintCount++;
+      }
     }
 
     //
@@ -1051,6 +1068,10 @@ PeiFreePages (
   if (MemoryAllocationHob != NULL) {
     UpdateOrSplitMemoryAllocationHob (PeiServices, MemoryAllocationHob, Memory, Bytes, EfiConventionalMemory);
     FreeMemoryAllocationHob (PrivateData, MemoryAllocationHob);
+    if (!PrivateData->PeiMemoryInstalled && (PrivateData->FreeMemorySearchHintCount < MAX_UINTN)) {
+      PrivateData->FreeMemorySearchHintCount++;
+    }
+
     return EFI_SUCCESS;
   } else {
     return EFI_NOT_FOUND;

MdeModulePkg/Core/Pei/PeiMain.h

@@ -353,6 +353,11 @@ struct _PEI_CORE_INSTANCE {
   // This is used for the memory bin feature, if enabled, to track bin locations.
   //
   EFI_MEMORY_TYPE_STATISTICS        *MemoryTypeStatistics;
+
+  ///
+  /// Count pre-memory events that may produce reusable conventional-memory ranges.
+  ///
+  UINTN                             FreeMemorySearchHintCount;
 };
 
 ///