Compiler-Runtime Mapping: Expanded Case Study

Expanded case study

Expanded Case Study for Compiler-Runtime Mapping is anchored on Compile-time mapping accuracy versus runtime adaptation gain for changing input shapes.. Convert measurements into mechanism-backed decisions with clear owner accountability.

Use this page to rehearse incident closure: symptom intake, mechanism split, evidence request, owner assignment, bounded fix, and release decision.

Incident memo

ACCELERATOR REVIEW MEMO - Scheduling & Workload Mapping / Compiler-Runtime Mapping

1. Symptom
   - Failing metric: Compile-time mapping accuracy versus runtime adaptation gain for changing input shapes.
   - Workload or traffic slice: <name>
   - First failing layer or stage: <operator, schedule, memory, runtime>
   - Build and runtime tags: <compiler/firmware/runtime/hardware>

2. Mechanism hypothesis
   - Primary mechanism: Compiler-runtime mapping defines how static optimization and dynamic control cooperate. The compiler captures graph-level transforms such as fusion, layout selection, and initial placement, producing executable plans tuned for expected workload envelopes. The runtime then adapts launch parameters, stream priorities, and memory residency as live traffic and input shape distributions drift. High-performing systems expose feedback loops where runtime telemetry informs compiler heuristics, reducing mismatch between offline assumptions and production behavior.
   - Competing hypotheses: <dataflow mismatch, memory stalls, precision drift, thermal limits>
   - Missing evidence: <counter packet, trace, replay, signoff data>

3. Proposed action
   - Smallest reversible change: <mapping/runtime/policy/config>
   - Expected movement: <throughput, p99 latency, perf-per-watt>
   - Regression risk: correctness, quality, thermal, software compatibility

4. Signoff
   - Required artifact: Closed-loop mapping report combining offline compile profiles with runtime telemetry and retuning actions.
   - Required owners: compiler lead, runtime lead, observability engineer, model serving architect
   - Final decision: ship, bounded rollout, rollback, or escalate

AI accelerator deep dive

Scheduling quality decides whether architecture headroom reaches product throughput.

Concept diagram

SCHEDULING PIPELINE

compile plan -> runtime queue -> core placement -> completion and tail behavior

Metric graph

TAIL-LATENCY DRIVERS

queueing delay      ███████
core imbalance      █████
mapping fallback    ████

Metrics and artifacts to collect

• queue wait profile

• batch policy impact

• core-level fairness

• operator fusion effect

Mini case study

Aggressive fusion reduced launch overhead but increased memory bursts that worsened p95 latency.

Debug branches

• Inspect tail first, not average

• Check fairness across streams

• Validate fusion against memory constraints

Senior review question

Ask: which first-principles bottleneck class explains the symptom, and what artifact proves it reproducibly?

Key takeaways

• Tie every accelerator claim to a reproducible workload slice and one primary metric trend.

• Prefer bounded fixes with clear owner and rollback boundary over broad tuning bundles.

Common pitfalls

• Optimizing synthetic kernels without production-shape validation.

• Reading average latency while ignoring p95 and p99 behavior.

• Declaring sparse or precision wins without fallback and quality evidence.

Principal accelerator review addendum

Compiler-Runtime Mapping should be framed as a full-system behavior, not an isolated kernel trick. Production outcomes are set by model shape mix, compiler choices, runtime queueing policy, memory hierarchy limits, and silicon delivery margins.

Compiler-runtime mapping defines how static optimization and dynamic control cooperate. The compiler captures graph-level transforms such as fusion, layout selection, and initial placement, producing executable plans tuned for expected workload envelopes. The runtime then adapts launch parameters, stream priorities, and memory residency as live traffic and input shape distributions drift. High-performing systems expose feedback loops where runtime telemetry informs compiler heuristics, reducing mismatch between offline assumptions and production behavior. A useful explanation always ties observed symptom to a repeatable path where useful work was blocked, delayed, or diluted by overhead.

Use Compile-time mapping accuracy versus runtime adaptation gain for changing input shapes. as an alarm, then anchor action using hard evidence such as Closed-loop mapping report combining offline compile profiles with runtime telemetry and retuning actions..

Scheduling determines whether hardware capability converts into SLA-level throughput and latency. Senior reviews expect a chain of proof: workload intent -> mapping -> hardware behavior -> product impact.

Use this addendum to force explicit owner assignment, bounded fixes, and reproducible evidence before declaring closure.