TEST-XSTAMP-PERF-001: Verify IOCTL_AVB_PHC_CROSSTIMESTAMP P50/P99 Latency

[zarfld]

Requirement

Derived from #48 (REQ-F-IOCTL-XSTAMP-001) performance requirements:

Metric	Target
IOCTL Latency (P50)	<8µs
IOCTL Latency (P99)	<15µs
Throughput (Single Thread)	>80K ops/sec

Test Objective

Measure the round-trip latency of IOCTL_AVB_PHC_CROSSTIMESTAMP from user-mode
DeviceIoControl call to return over 10,000 calls and verify P50 and P99 are
within the budgets specified in REQ-F-IOCTL-XSTAMP-001.

Test Cases

TC-XSTAMP-PERF-001a: 10K calls — P50 < 8µs, P99 < 15µs

Preconditions: Driver loaded, handle open, adapter index 0 valid.

Steps:

1. Allocate array of 10,000 latency samples (microseconds, double precision)
2. For i = 0..9999:
   a. QueryPerformanceCounter(&t0)
   b. DeviceIoControl(IOCTL_AVB_PHC_CROSSTIMESTAMP, &req, ...)
   c. QueryPerformanceCounter(&t1)
   d. Assert req.valid == 1
   e. samples[i] = (t1 - t0) * 1e6 / qpc_freq
3. Sort samples[]
4. Report P50, P95, P99, P99.9

Acceptance Criteria:

• P50 < 8µs (REQ-F-IOCTL-XSTAMP-001: IOCTL Latency P50 target)
• P99 < 15µs (REQ-F-IOCTL-XSTAMP-001: IOCTL Latency P99 target)

Expected Status: ⚠️ P99 may exceed 15µs under OS scheduling jitter — this is a known
measurement challenge for user-mode latency tests; note whether system was under load.

---

TC-XSTAMP-PERF-001b: Throughput > 80K ops/sec (single thread)

Steps:

1. Record wall time via QPC
2. Call IOCTL_AVB_PHC_CROSSTIMESTAMP in a tight loop for 1 second
3. Count successful calls
4. Assert count > 80,000

Acceptance Criterion: ops/sec > 80,000

---

TC-XSTAMP-PERF-001c: All 10K responses have valid == 1

Acceptance Criterion: No IOCTL fails during the latency run (driver stability)

Acceptance Criteria Summary

• ✅ P50 latency < 8µs over 10K calls
• ✅ P99 latency < 15µs over 10K calls
• ✅ Throughput > 80K ops/sec sustained
• ✅ valid == 1 for all responses (no silent failures)

Implementation

• New test file: tests/integration/ptp/ptp_ioctl_latency_test.c

Traceability

• Traces to: REQ-F-IOCTL-XSTAMP-001: Cross-Timestamp Query (PHC + System Time) #48 (REQ-F-IOCTL-XSTAMP-001: Cross-Timestamp Query — PHC + System Time)

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❌ Test Requirements Missing

Test cases must link to the requirements they verify.

Required Action

Add the following to your issue body:

## Verified Requirements
- #N (REQ-F or REQ-NF issue)

Or in the description:

Verifies: #N, #M (requirement issues)

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