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Assets/Mirror/Core/Tools/TimeSample.cs

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+// TimeSample from Mirror II.
+// simple profiling sample, averaged for display in statistics.
+// usable in builds without unitiy profiler overhead etc.
+//
+// .average may safely be called from main thread while Begin/End is in another.
+// i.e. worker threads, transport, etc.
+using System.Diagnostics;
+using System.Threading;
+
+namespace Mirror
+{
+    public struct TimeSample
+    {
+        // UnityEngine.Time isn't thread safe. use stopwatch instead.
+        readonly Stopwatch watch;
+
+        // remember when Begin was called
+        double beginTime;
+
+        // keep accumulating times over the given interval.
+        // (not readonly. we modify its contents.)
+        ExponentialMovingAverage ema;
+
+        // average in seconds.
+        // code often runs in sub-millisecond time. float is more precise.
+        //
+        // set with Interlocked for thread safety.
+        // can be read from main thread while sampling happens in other thread.
+        public double average; // THREAD SAFE
+
+        // average over N begin/end captures
+        public TimeSample(int n)
+        {
+            watch     = new Stopwatch();
+            watch.Start();
+            ema       = new ExponentialMovingAverage(n);
+            beginTime = 0;
+            average   = 0;
+        }
+
+        // begin is called before the code to be sampled
+        public void Begin()
+        {
+            // remember when Begin was called.
+            // keep StopWatch running so we can average over the given interval.
+            beginTime = watch.Elapsed.TotalSeconds;
+            // Debug.Log($"Begin @ {beginTime:F4}");
+        }
+
+        // end is called after the code to be sampled
+        public void End()
+        {
+            // add duration in seconds to accumulated durations
+            double elapsed = watch.Elapsed.TotalSeconds - beginTime;
+            ema.Add(elapsed);
+
+            // expose new average thread safely
+            Interlocked.Exchange(ref average, ema.Value);
+        }
+    }
+}