msd

Metric: MSD (Missed System Delivery / Pacing Risk-Zone)

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Executive Summary

MSD is an autonomous diagnostic sensor. It tracks when the system (GPU + Compositor + OS Scheduler) fails to maintain a deterministic rendering cadence. It operates independently of any pacing controllers (like --pll) to provide an unvarnished view of your display stack's stability.

• MSD = 0: The system is delivering frames within the safe, predictable window.
• MSD > 0: The system is "redlining." Even if you don't see a skip yet, the timing has crossed the mathematical safety limit.

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The Dynamic Threshold (The 1.4x / +4ms Rule)

The tool calculates a Dynamic Risk-Zone based on your monitor's refresh rate ($Hz$). This "tripwire" is positioned at the edge of stability, the point where jitter becomes high enough to threaten the next vblank pulse.

$$ActiveThreshold = FrameBudget + \min(4.0ms, FrameBudget \times 0.4)$$

Refresh Rate	Ideal Period	MSD Threshold (1.4x)
60 Hz	16.66ms	20.66ms
120 Hz	8.33ms	11.66ms
144 Hz	6.94ms	9.71ms

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Why MSD Matters Without --pll

When running in default mode (uncapped or standard VSync), the MSD acts as a stress-test monitor:

1. Compositor Jitter: Reveals if the compositor is holding buffers inconsistently.
2. Scheduling Noise: Detects if background OS tasks are pushing frame delivery into the Risk-Zone.
3. Hardware Saturation: Identifies the exact cube count where the GPU can no longer keep the "vibe" of 120Hz/144Hz fluidity.

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How to Interpret the Count

State	Result
Safe Zone	Frame is within $Budget + Margin$. MSD remains 0.
Risk Zone	$Delta > Threshold$. MSD increments to signal Pacing Fragility.
Pulse Miss	$Delta > 2 \times Budget$. MSD increments by the number of hardware pulses lost.

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Troubleshooting

• High MSD without --pll: Your system has high DPC latency or the compositor's scheduling is non-deterministic. The "smoothness" you think you see is actually a series of near-misses.
• MSD drops to 0 when using --pll: This proves the hardware is capable, and the previous issues were purely due to poor frame-scheduling phase alignment.