From: Ni, Ray <ray.ni@intel.com>
Sent: Thursday, November 09, 2023 10:36 AM
To: Jin, Zhi <zhi.jin@intel.com>; devel@edk2.groups.io
Cc: Wang, Jian J <jian.j.wang@intel.com>; Gao, Liming <gaoliming@byosoft.com.cn>; Bi, Dandan <dandan.bi@intel.com>
Subject: Re: [PATCH 1/1] MdeModulePkg: Optimize CoreInstallMultipleProtocolInterfaces

CoreLocateDevicePath is used in CoreInstallMultipleProtocolInterfaces to
check if a Device Path Protocol instance with the same device path is
alreay installed.
CoreLocateDevicePath is a generic API, and would introduce some
unnecessary overhead for such usage.

The optimization is:
1. Implement IsDevicePathInstalled to loop all the Device Path
   Protocols installed and check if any of them matchs the given device
   path.
2. Replace CoreLocateDevicePath with IsDevicePathInstalled in
   CoreInstallMultipleProtocolInterfaces.

This optimization could save several seconds in PCI enumeration on a
system with many PCI devices.

Cc: Jian J Wang <jian.j.wang@intel.com>
Cc: Liming Gao <gaoliming@byosoft.com.cn>
Cc: Dandan Bi <dandan.bi@intel.com>
Cc: Ray Ni <ray.ni@intel.com>
Signed-off-by: Zhi Jin <zhi.jin@intel.com>
---
 MdeModulePkg/Core/Dxe/Hand/Handle.c | 74 +++++++++++++++++++++++++----
 1 file changed, 64 insertions(+), 10 deletions(-)

diff --git a/MdeModulePkg/Core/Dxe/Hand/Handle.c b/MdeModulePkg/Core/Dxe/Hand/Handle.c
index bd6c57843e..a08cf19bfd 100644
--- a/MdeModulePkg/Core/Dxe/Hand/Handle.c
+++ b/MdeModulePkg/Core/Dxe/Hand/Handle.c
@@ -197,6 +197,66 @@ CoreFindProtocolInterface (
   return Prot;
 }
 
+/**
+  Check if the given device path is already installed
+
+  @param  DevicePath            The given device path
+
+  @retval TRUE                  The device path is already installed
+  @retval FALSE                 The device path is not installed
+
+**/
+BOOLEAN
+IsDevicePathInstalled (
+  IN EFI_DEVICE_PATH_PROTOCOL  *DevicePath
+  )
+{
+  UINTN                     SourceSize;
+  UINTN                     Size;
+  BOOLEAN                   Found;
+  LIST_ENTRY                *Link;
+  PROTOCOL_ENTRY            *ProtEntry;
+  PROTOCOL_INTERFACE        *Prot;
+
+  if (DevicePath == NULL) {
+    return FALSE;
+  }
+
+  Found         = FALSE;
+  SourceSize    = GetDevicePathSize (DevicePath);
+  ASSERT (SourceSize >= END_DEVICE_PATH_LENGTH);
+
+  CoreAcquireProtocolLock ();
+  //
+  // Look up the protocol entry
+  //
+  ProtEntry = CoreFindProtocolEntry (&gEfiDevicePathProtocolGuid, FALSE);
+  if (ProtEntry == NULL) {
+    goto Done;
+  }
+
+  for (Link = ProtEntry->Protocols.ForwardLink; Link != &ProtEntry->Protocols; Link = Link->ForwardLink) {
+    //
+    // Loop on the DevicePathProtocol interfaces
+    //
+    Prot = CR (Link, PROTOCOL_INTERFACE, ByProtocol, PROTOCOL_INTERFACE_SIGNATURE);
+
+    //
+    // Check if DevicePath is same as this interface
+    //
+    Size = GetDevicePathSize (Prot->Interface);
+    ASSERT (Size >= END_DEVICE_PATH_LENGTH);
+    if ((Size == SourceSize) && (CompareMem (DevicePath, Prot->Interface, Size - END_DEVICE_PATH_LENGTH) == 0)) {
+      Found = TRUE;
+      break;
+    }
+  }
+
+Done:
+  CoreReleaseProtocolLock ();
+  return Found;
+}
+
 /**
   Removes an event from a register protocol notify list on a protocol.
 
@@ -517,8 +577,6 @@ CoreInstallMultipleProtocolInterfaces (
   EFI_TPL                   OldTpl;
   UINTN                     Index;
   EFI_HANDLE                OldHandle;
-  EFI_HANDLE                DeviceHandle;
-  EFI_DEVICE_PATH_PROTOCOL  *DevicePath;
 
   if (Handle == NULL) {
     return EFI_INVALID_PARAMETER;
@@ -548,14 +606,10 @@ CoreInstallMultipleProtocolInterfaces (
     //
     // Make sure you are installing on top a device path that has already been added.
     //
-    if (CompareGuid (Protocol, &gEfiDevicePathProtocolGuid)) {
-      DeviceHandle = NULL;
-      DevicePath   = Interface;
-      Status       = CoreLocateDevicePath (&gEfiDevicePathProtocolGuid, &DevicePath, &DeviceHandle);
-      if (!EFI_ERROR (Status) && (DeviceHandle != NULL) && IsDevicePathEnd (DevicePath)) {
-        Status = EFI_ALREADY_STARTED;
-        continue;
-      }
+    if (CompareGuid (Protocol, &gEfiDevicePathProtocolGuid) &&
+        IsDevicePathInstalled (Interface)) {
+      Status = EFI_ALREADY_STARTED;
+      continue;
     }
 
     //
--
2.39.2