Use high resolution timer on Windows (#3478)

This PR fixes timing issues on Windows. Simulation ratios have been observed as low as 6.5% on Windows with an empty scene, and simulation rates often hover around 80% with busier scenes. The problem was caused by the loop rate stabilization strategy. By default the Windows kernel timing resolution is 15.6 ms, meaning that a normal sleep command can not wake before 15.6 ms. On older version of Windows, a system-wide command was used to modify the system timing resolution, meaning that if any process requested a higher timing resolution all timers would also have this resolution. Newer Windows updates have changed this behavior, and each high resolution timer must now use the CREATE_WAITABLE_TIMER_HIGH_RESOLUTION with the Win32 API function CreateWaitableTimerEx() to create a timer that has the higher resolution capability.

This PR modifies the SimulationRunner class to use a high resolution timer instead of std::this_thread::sleep_until() when on Windows.

---------

Signed-off-by: John Wason <wason@wasontech.com>
(cherry picked from commit 503bc6b)

# Conflicts:
#	src/SimulationRunner.hh

Author: johnwason

src/SimulationRunner.cc

@@ -66,6 +66,16 @@
 #include "LevelManager.hh"
 #include "SdfGenerator.hh"
 
+#ifdef _WIN32
+#ifndef NOMINMAX
+#define NOMINMAX
+#endif
+#ifndef WIN32_LEAN_AND_MEAN
+#define WIN32_LEAN_AND_MEAN
+#endif
+#include <windows.h>
+#endif
+
 using namespace gz;
 using namespace sim;
 
@@ -103,6 +113,34 @@ struct MaybeGilScopedRelease
 
 }
 
+#ifdef _WIN32
+namespace gz
+{
+namespace sim
+{
+inline namespace GZ_SIM_VERSION_NAMESPACE {
+// Utility class to store the windows HANDLE variable and close
+// the handle using RAII. This class also hides the HANDLE
+// type from the global header files.
+class SimulationRunnerWinHandleStorage
+{
+  private: HANDLE handleStorage{NULL};
+
+  public: HANDLE handle() { return handleStorage; }
+
+  public: SimulationRunnerWinHandleStorage(HANDLE h) : handleStorage(h) {}
+
+  public: ~SimulationRunnerWinHandleStorage() {
+    if (handleStorage != NULL)
+    {
+      CloseHandle(handleStorage);
+    }
+  }
+};
+}
+}
+}
+#endif
 
 //////////////////////////////////////////////////
 SimulationRunner::SimulationRunner(const sdf::World &_world,
@@ -181,6 +219,16 @@ SimulationRunner::SimulationRunner(const sdf::World &_world,
   );
   this->currentInfo.simTime = this->simTimeEpoch;
 
+#ifdef _WIN32
+  HANDLE winPrecisionTimerHandle = CreateWaitableTimerExA(NULL, NULL,
+    CREATE_WAITABLE_TIMER_HIGH_RESOLUTION, TIMER_ALL_ACCESS);
+  if (winPrecisionTimerHandle != NULL)
+  {
+    winPrecisionTimer = std::make_unique<SimulationRunnerWinHandleStorage>(
+      winPrecisionTimerHandle);
+  }
+#endif
+
   // World control
   transport::NodeOptions opts;
   std::string ns{"/world/" + this->worldName};
@@ -872,14 +920,45 @@ bool SimulationRunner::Run(const uint64_t _iterations)
       // larger than the typical OS + CPU C-state latency.
       constexpr auto kSpinThreshold = 200us;
 
+      auto now = std::chrono::steady_clock::now();
+
       // If the scheduled update time is in the future...
-      if (nextUpdateTime > std::chrono::steady_clock::now())
+      if (nextUpdateTime > now)
       {
         // ...sleep until we are close to the target time.
         auto sleepTarget = nextUpdateTime - kSpinThreshold;
-        if (sleepTarget > std::chrono::steady_clock::now())
+        if (sleepTarget > now)
         {
+#ifndef _WIN32
           std::this_thread::sleep_until(sleepTarget);
+#else
+          if (winPrecisionTimer)
+          {
+            auto sleepTargetDuration =
+              std::chrono::duration_cast<std::chrono::microseconds>(
+              sleepTarget - now);
+            LARGE_INTEGER due_time;
+            memset(&due_time, 0, sizeof(due_time));
+            // Positive durations are absolute, while negative durations
+            // are relative in 10 us intervals.
+            // The absolute time uses the non-precision system clock so we
+            // need to use relative time.
+            due_time.QuadPart = -sleepTargetDuration.count() * 10;
+            if (SetWaitableTimer(winPrecisionTimer->handle(), &due_time, 0,
+              NULL, NULL, FALSE) != TRUE)
+            {
+              gzerr << "Could not SetWaitableTimer" << std::endl;
+            }
+            else
+            {
+              WaitForSingleObject(winPrecisionTimer->handle(), INFINITE);
+            }
+          }
+          else
+          {
+            std::this_thread::sleep_until(sleepTarget);
+          }
+#endif
         }
 
         // ...then busy-wait for the final moments for precision.
@@ -890,7 +969,7 @@ bool SimulationRunner::Run(const uint64_t _iterations)
       }
 
       // Schedule the next update time.
-      auto now = std::chrono::steady_clock::now();
+      now = std::chrono::steady_clock::now();
       nextUpdateTime += this->updatePeriod;
       if (nextUpdateTime < now)
       {

src/SimulationRunner.hh

@@ -69,6 +69,9 @@ namespace gz
     inline namespace GZ_SIM_VERSION_NAMESPACE {
     // Forward declarations.
     class SimulationRunnerPrivate;
+#ifdef _WIN32
+    class SimulationRunnerWinHandleStorage;
+#endif
 
     class GZ_SIM_VISIBLE SimulationRunner
     {
@@ -541,6 +544,23 @@ namespace gz
       private: bool threadsNeedCleanUp{false};
 
       private: bool resetInitiated{false};
+<<<<<<< HEAD
+=======
+
+      /// \brief True to create entities.
+      private: bool createEntities{false};
+      private: bool entitiesCreated{false};
+
+      /// \brief Flag indicating if the server encountered errors during
+      /// initialization and should exit immediately. See
+      /// `SetExitedWithErrors()`.
+      private: bool exitedWithErrors{false};
+#ifdef _WIN32
+      private: std::unique_ptr<SimulationRunnerWinHandleStorage>
+        winPrecisionTimer;
+#endif
+
+>>>>>>> 503bc6b0 (Use high resolution timer on Windows (#3478))
       friend class LevelManager;
     };
     }