From 3d86ecd94dae0936cfa770b001473921119ee18e Mon Sep 17 00:00:00 2001
From: Philip Rebohle <philip.rebohle@tu-dortmund.de>
Date: Thu, 18 Jul 2019 22:52:20 +0200
Subject: [PATCH] [dxvk] Estimate GPU idle time based on cleanup thread
 activity

We'll assume that GPU idle time == time spent waiting for new
command lists to be added to the queue of the cleanup thread.
This isn't entirely accurate, especially if CPU load is very
high, but should be good enough.
---
 src/dxvk/dxvk_queue.cpp | 13 ++++++++++---
 src/dxvk/dxvk_queue.h   | 13 +++++++++++++
 2 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/src/dxvk/dxvk_queue.cpp b/src/dxvk/dxvk_queue.cpp
index 53cf838b1..746475a22 100644
--- a/src/dxvk/dxvk_queue.cpp
+++ b/src/dxvk/dxvk_queue.cpp
@@ -137,9 +137,16 @@ namespace dxvk {
     std::unique_lock<std::mutex> lock(m_mutex);
 
     while (!m_stopped.load()) {
-      m_submitCond.wait(lock, [this] {
-        return m_stopped.load() || !m_finishQueue.empty();
-      });
+      if (m_finishQueue.empty()) {
+        auto t0 = std::chrono::high_resolution_clock::now();
+
+        m_submitCond.wait(lock, [this] {
+          return m_stopped.load() || !m_finishQueue.empty();
+        });
+
+        auto t1 = std::chrono::high_resolution_clock::now();
+        m_gpuIdle += std::chrono::duration_cast<std::chrono::microseconds>(t1 - t0).count();
+      }
 
       if (m_stopped.load())
         return;
diff --git a/src/dxvk/dxvk_queue.h b/src/dxvk/dxvk_queue.h
index 59b77fb87..50ea26b52 100644
--- a/src/dxvk/dxvk_queue.h
+++ b/src/dxvk/dxvk_queue.h
@@ -80,6 +80,18 @@ namespace dxvk {
     uint32_t pendingSubmissions() const {
       return m_pending.load();
     }
+
+    /**
+     * \brief Retrieves estimated GPU idle time
+     *
+     * This is a monotonically increasing counter
+     * which can be evaluated periodically in order
+     * to calculate the GPU load.
+     * \returns Accumulated GPU idle time, in us
+     */
+    uint64_t gpuIdleTicks() const {
+      return m_gpuIdle.load();
+    }
     
     /**
      * \brief Submits a command list asynchronously
@@ -147,6 +159,7 @@ namespace dxvk {
     
     std::atomic<bool>       m_stopped = { false };
     std::atomic<uint32_t>   m_pending = { 0u };
+    std::atomic<uint64_t>   m_gpuIdle = { 0ull };
 
     std::mutex              m_mutex;
     std::mutex              m_mutexQueue;