From 0dbd59ae85e460f5b21b461d01c973b2c55e38e2 Mon Sep 17 00:00:00 2001
From: Alexandre Mutel <alexandre@unity3d.com>
Date: Mon, 16 Dec 2024 18:53:34 +0100
Subject: [PATCH] Fix compressed frames

---
 src/Ultra.Sampler/MacOS/MacOSUltraSampler.cs | 16 ++++++++--------
 src/Ultra.Sampler/UltraSamplerSource.cs      | 16 +++++++++++-----
 2 files changed, 19 insertions(+), 13 deletions(-)

diff --git a/src/Ultra.Sampler/MacOS/MacOSUltraSampler.cs b/src/Ultra.Sampler/MacOS/MacOSUltraSampler.cs
index 48ba412..96dd4f9 100644
--- a/src/Ultra.Sampler/MacOS/MacOSUltraSampler.cs
+++ b/src/Ultra.Sampler/MacOS/MacOSUltraSampler.cs
@@ -19,7 +19,7 @@ internal unsafe class MacOSUltraSampler : UltraSampler
     private Thread? _samplerThread;
     private ulong _samplerThreadId;
     private readonly AutoResetEvent _samplerResumeThreadEvent;
-    
+
     // Frames information
     private const int MaximumFrames = 4096;
     private readonly ulong[] _frames; // 32 KB
@@ -366,7 +366,6 @@ private unsafe void Sample(MacOS.MacOSLibSystem.mach_port_t rootTask, NativeSamp
             // Compute the same frame count
             var sameFrameCount = ComputeSameFrameCount(threadInfo.thread_id, frameCount, pFrames);
             frameCount -= sameFrameCount;
-            pFrames += sameFrameCount;
 
             // Long only the delta frames
             samplingDelegate(threadInfo.thread_id, (int)threadExtendedInfo.pth_run_state, (int)threadExtendedInfo.pth_cpu_usage, sameFrameCount, frameCount * sizeof(ulong), (byte*)pFrames);
@@ -387,9 +386,10 @@ private unsafe void Sample(MacOS.MacOSLibSystem.mach_port_t rootTask, NativeSamp
         // Swap the active and current thread ids
         (_currentThreadIds, _activeThreadIds) = (_activeThreadIds, _currentThreadIds);
     }
-    
+
     private int ComputeSameFrameCount(ulong threadId, int frameCount, ulong* frames)
     {
+        int originalFrameCount = frameCount;
         // We limit the frame recording to MaximumCompressedFrameCount
         frameCount = Math.Min(frameCount, MaximumCompressedFrameCount);
 
@@ -421,10 +421,10 @@ private int ComputeSameFrameCount(ulong threadId, int frameCount, ulong* frames)
             int previousFrameCount = (int)previousFrame;
             previousFrame = ref Unsafe.Add(ref previousFrame, 1);
 
-            var minFrameCount = Math.Min(previousFrameCount, frameCount);
-            for (; sameFrameCount < minFrameCount; sameFrameCount++)
+            var maxFrameCount = Math.Min(previousFrameCount, frameCount);
+            for (; sameFrameCount < maxFrameCount; sameFrameCount++)
             {
-                if (frames[sameFrameCount] != previousFrame)
+                if (frames[originalFrameCount - sameFrameCount - 1] != previousFrame)
                 {
                     break;
                 }
@@ -439,9 +439,9 @@ private int ComputeSameFrameCount(ulong threadId, int frameCount, ulong* frames)
         previousFrame = ref Unsafe.Add(ref previousFrame, 1);
         for (int i = 0; i < frameCount; i++)
         {
-            Unsafe.Add(ref previousFrame, i) = frames[i];
+            Unsafe.Add(ref previousFrame, i) = frames[originalFrameCount - i - 1];
         }
-        
+
         return sameFrameCount;
     }
 
diff --git a/src/Ultra.Sampler/UltraSamplerSource.cs b/src/Ultra.Sampler/UltraSamplerSource.cs
index 31236e5..db2fb4a 100644
--- a/src/Ultra.Sampler/UltraSamplerSource.cs
+++ b/src/Ultra.Sampler/UltraSamplerSource.cs
@@ -21,14 +21,20 @@ private UltraSamplerSource()
     [UnconditionalSuppressMessage("Trimming", "IL2026:Members annotated with 'RequiresUnreferencedCodeAttribute' require dynamic access otherwise can break functionality when trimming application code", Justification = "<Pending>")]
     public unsafe void NativeCallstack(ulong threadId, int threadState, int threadCpuUsage, int previousFrameCount, int framesSize, byte* frames) // frames is last to allow perfview to visualize previous fixed size arguments and also, it is an ulong otherwise the EventSource will silently fail to register!
     {
-        var evt = stackalloc EventData[3];
+        var evt = stackalloc EventData[6];
         evt[0].DataPointer = (nint)(void*)&threadId;
         evt[0].Size = sizeof(ulong);
-        evt[1].DataPointer = (nint)(void*)&framesSize;
+        evt[1].DataPointer = (nint)(void*)&threadState;
         evt[1].Size = sizeof(int);
-        evt[2].DataPointer = (nint)(void*)&frames;
-        evt[2].Size = framesSize;
-        WriteEventCore(UltraSamplerConstants.NativeCallStackEventId, 3, evt);
+        evt[2].DataPointer = (nint)(void*)&threadCpuUsage;
+        evt[2].Size = sizeof(int);
+        evt[3].DataPointer = (nint)(void*)&previousFrameCount;
+        evt[3].Size = sizeof(int);
+        evt[4].DataPointer = (nint)(void*)&framesSize;
+        evt[4].Size = sizeof(int);
+        evt[5].DataPointer = (nint)(void*)frames;
+        evt[5].Size = framesSize;
+        WriteEventCore(UltraSamplerConstants.NativeCallStackEventId, 6, evt);
     }
 
     [Event(UltraSamplerConstants.NativeModuleEventId, Level = EventLevel.Informational, Task = (EventTask)UltraSamplerConstants.TaskNativeModuleEventId)]