Gamepad input causes frametime inconsistency while PresentMon is running

[DevTechProfile]

When using a gamepad in Final Fantasy 7 Rebirth, I observe noticeable frametime inconsistencies/stuttering that only occurs while PresentMon is running. This issue does not reproduce when using RTSS (RivaTuner Statistics Server) for frametime monitoring. I've tested RTSS using different frametime calculation points, just to be sure.

See attached graph. The first half of the measurement shows mouse-only input (consistent frametimes), while the second half shows the impact after switching to gamepad input. Frametimes were recorded with PresentMon console only!

To point this out, when PresentMon is running while using the gamepad, even RTSS frametimes show inconsistency issues. The impact is system-wide.

PresentMon-2026-01-25T181722.csv

Environment:

• PresentMon Version 2.4.1
• Processor AMD Ryzen 7 9800X3D
• System RAM 32GB (2x16GB) 6000MT/s
• Graphics Card NVIDIA GeForce RTX 5090
• Motherboard ASUSTeK COMPUTER INC. ROG STRIX X670E-E GAMING WIFI
• OS Version Microsoft Windows 11 Pro Build 26200
• GPU Driver Version 591.74
• API DX12
• Windows Game Mode Enabled
• HAGS Enabled
• Presentation Mode Fullscreen Optimized or Borderless

[DevTechProfile]

Problem: When PC Latency tracking is enabled, PCLStatsInput/ReflexStatsInput ETW events fire on every input (including gamepad at 100-1000Hz). Each event triggered an expensive TdhGetEventInformation() call in the TIME_CRITICAL consumer thread, causing system-wide scheduling interference and frametime inconsistencies.

Solution: Cache the PCL event type after first decode using (EventId, Opcode, Level) as key. For StatsInput events (which only need processId and timestamp from the header), skip TDH decoding entirely on subsequent events.

Files changed:

• PresentData/PresentMonTraceConsumer.hpp
• PresentData/PresentMonTraceConsumer.cpp

PresentMonTraceConsumer.zip
CX_PresentMon-2.4.2-x64.zip

[DevTechProfile]

PCL Performance Investigation Summary

Issue

Performance degradation (frame time issues) when PC latency tracking (--track_pc_latency) is enabled, specifically with FF7 Rebirth.

Investigation Steps

1. Initial Hypothesis: TDH Decode Overhead

• PCL events require TdhGetEventInformation calls to decode TraceLogging events
• Fix Applied: Implemented event type caching to skip TDH decode for known event types
• Result: Cache working (1 miss), but issue persisted

2. StatsEvent Processing Optimization

• StatsEvent was still doing TDH decode even with cache hit
• Fix Applied: Direct payload reading for StatsEvent (Marker at offset 0, FrameID at offset 4)
• Result: Issue persisted

3. ETW Delivery Overhead Test

• Disabled ALL PCL processing (just count events, return immediately)
• Result: Issue persisted with FF7 Rebirth
• Conclusion: Suspected ETW infrastructure overhead

4. Cross-Game Comparison

Game	StatsEvents/sec	InputEvents/sec	Performance Issue
FF7 Rebirth	~970	~970 (gamepad)	YES
FF7 Rebirth	~970	0	YES
Dying Light: The Beast	~1300	0	NO

Root Cause

Game-specific issue with FF7 Rebirth, not PresentMon code or general ETW overhead.

Evidence:

• Dying Light generates MORE events (~1300/sec vs ~970/sec) with NO performance issues
• Same PresentMon code path, same PCL provider, same optimizations
• FF7 Rebirth has issues even when PresentMon skips all event processing

Optimizations Retained

1. Event type cache - Avoids TDH decode for repeated events (PresentMonTraceConsumer.cpp)
2. Direct payload reading - StatsEvent reads Marker/FrameID directly from UserData
3. HandlePclStatsEvent helper - Centralized marker processing

Files Modified

• PresentData/PresentMonTraceConsumer.hpp - Added PclDiagnostics struct, HandlePclStatsEvent declaration
• PresentData/PresentMonTraceConsumer.cpp - Event caching, direct payload reading, diagnostics
• PresentData/PresentMonTraceSession.cpp - Provider enablement (unchanged functionally)

Recommendation

The issue appears to be specific to FF7 Rebirth's Reflex/PCL implementation or its interaction with the NVIDIA driver. Consider:

1. Reporting to NVIDIA as a potential Reflex SDK issue
2. Reporting to Square Enix as a game-specific bug
3. Documenting as a known limitation for this specific title

Diagnostic Code (not pushed)

Diagnostics can be enabled by checking for PCL: messages in DebugView. Output includes:

• In= StatsInput event count
• Ev= StatsEvent count
• Hits/Miss= Cache statistics
• Map= PCL timing data map size
• Fuzz= Fuzzy search iterations
• Clean= Cleanup iterations