From 0a883ab651ec5e496c3bb39072cd3cb5f13cf3bc Mon Sep 17 00:00:00 2001
From: Conn O'Griofa <connogriofa@gmail.com>
Date: Mon, 4 Jan 2021 04:45:46 +0000
Subject: [PATCH] Use realtime GPU priority to avoid stalls during high GPU
 usage

Change derived from OBS project commit: https://github.com/obsproject/obs-studio/commit/ec769ef008b748f7dfba211daec9eb203ea4bea0
See related discussion: https://obsproject.com/forum/threads/obs-studio-24-0-3-gpu-priority-fix-testing.111669/
---
 sunshine/platform/windows/display.h        | 13 ++++++++++
 sunshine/platform/windows/display_base.cpp | 30 ++++++++++++++++++++++
 2 files changed, 43 insertions(+)

diff --git a/sunshine/platform/windows/display.h b/sunshine/platform/windows/display.h
index 662115e8..039e6a75 100644
--- a/sunshine/platform/windows/display.h
+++ b/sunshine/platform/windows/display.h
@@ -84,6 +84,19 @@ public:
 
   DXGI_FORMAT format;
   D3D_FEATURE_LEVEL feature_level;
+
+  typedef enum _D3DKMT_SCHEDULINGPRIORITYCLASS
+  {
+    D3DKMT_SCHEDULINGPRIORITYCLASS_IDLE,
+    D3DKMT_SCHEDULINGPRIORITYCLASS_BELOW_NORMAL,
+    D3DKMT_SCHEDULINGPRIORITYCLASS_NORMAL,
+    D3DKMT_SCHEDULINGPRIORITYCLASS_ABOVE_NORMAL,
+    D3DKMT_SCHEDULINGPRIORITYCLASS_HIGH,
+    D3DKMT_SCHEDULINGPRIORITYCLASS_REALTIME
+  }
+  D3DKMT_SCHEDULINGPRIORITYCLASS;
+
+  typedef NTSTATUS WINAPI (*PD3DKMTSetProcessSchedulingPriorityClass)(HANDLE, D3DKMT_SCHEDULINGPRIORITYCLASS);
 };
 
 class display_ram_t : public display_base_t {
diff --git a/sunshine/platform/windows/display_base.cpp b/sunshine/platform/windows/display_base.cpp
index 4b42880c..c510b044 100644
--- a/sunshine/platform/windows/display_base.cpp
+++ b/sunshine/platform/windows/display_base.cpp
@@ -206,6 +206,36 @@ int display_base_t::init() {
 
   // Bump up thread priority
   {
+    const DWORD flags = TOKEN_ADJUST_PRIVILEGES | TOKEN_QUERY;
+    TOKEN_PRIVILEGES tp;
+    HANDLE token;
+    LUID val;
+
+    if (OpenProcessToken(GetCurrentProcess(), flags, &token) &&
+       !!LookupPrivilegeValue(NULL, SE_INC_BASE_PRIORITY_NAME, &val)) {
+      tp.PrivilegeCount = 1;
+      tp.Privileges[0].Luid = val;
+      tp.Privileges[0].Attributes = SE_PRIVILEGE_ENABLED;
+
+      if (!AdjustTokenPrivileges(token, false, &tp, sizeof(tp), NULL, NULL)) {
+        BOOST_LOG(error) << "Could not set privilege to increase GPU priority";
+      }
+    }
+
+    CloseHandle(token);
+
+    HMODULE gdi32 = GetModuleHandleA("GDI32");
+    if (gdi32) {
+      PD3DKMTSetProcessSchedulingPriorityClass fn =
+        (PD3DKMTSetProcessSchedulingPriorityClass)GetProcAddress(gdi32, "D3DKMTSetProcessSchedulingPriorityClass");
+      if (fn) {
+        status = fn(GetCurrentProcess(), D3DKMT_SCHEDULINGPRIORITYCLASS_REALTIME);
+        if (FAILED(status)) {
+          BOOST_LOG(error) << "Failed to set realtime GPU priority. Please run application as administrator for optimal performance.";
+        }
+      }
+    }
+
     dxgi::dxgi_t::pointer dxgi_p {};
     status = device->QueryInterface(IID_IDXGIDevice, (void**)&dxgi_p);
     dxgi::dxgi_t dxgi { dxgi_p };