Performance-per-Watt Optimization Workflow: Debug Playbook

Debug playbook

Debug Playbook for Performance-per-Watt Optimization Workflow is anchored on Sustained throughput per watt under SLA-constrained load, including memory and host-orchestration overhead.. Convert measurements into mechanism-backed decisions with clear owner accountability.

1. Freeze workload seed, model revision, and execution environment.

2. Locate first persistent stage where metrics diverge.

3. Classify dominant mechanism: compute, memory, scheduling, precision, or thermal.

4. Build one focused reproducer and apply one bounded fix.

5. Re-run full correctness, quality, and performance matrix.

Review memo template

ACCELERATOR REVIEW MEMO - Power & Precision Tradeoffs / Performance-per-Watt Optimization Workflow

1. Symptom
   - Failing metric: Sustained throughput per watt under SLA-constrained load, including memory and host-orchestration overhead.
   - 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: Performance per watt improves when compute occupancy, memory locality, and scheduling policy are tuned as one system. Kernel fusion, tile-size alignment, and memory traffic shaping reduce wasted movement so each watt contributes to useful work. Runtime policies such as micro-batching, admission control, and stream prioritization can further lift efficiency if tail latency remains within target. The strongest gains come from iterative profiling loops that attribute energy to specific kernels, data paths, and idle intervals, then remove the dominant inefficiencies first.
   - 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: Perf-per-watt optimization report with bottleneck ranking, intervention plan, and before-after operating points.
   - Required owners: systems performance engineer, runtime scheduler owner, power modeling owner, capacity planning owner
   - Final decision: ship, bounded rollout, rollback, or escalate

AI accelerator deep dive

Precision and DVFS policy must be co-designed with quality guardrails and thermal behavior.

Concept diagram

PRECISION-POWER LOOP

numeric format choice -> throughput and energy
         + thermal state and DVFS policy -> sustained SLA

Metric graph

PERF/W TRADE

INT8 efficiency      █████████
BF16 stability       ██████
thermal clamp risk   ████

Metrics and artifacts to collect

• precision-mode mix

• perf-per-watt trend

• thermal clamp frequency

• quality regression monitor

Mini case study

Switching to lower precision improved nominal throughput, but thermal clamp cycles reduced sustained gains.

Debug branches

• Validate quality guardrails by slice

• Correlate thermal events to latency tails

• Audit precision fallback behavior

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

Performance-per-Watt Optimization Workflow 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.

Performance per watt improves when compute occupancy, memory locality, and scheduling policy are tuned as one system. Kernel fusion, tile-size alignment, and memory traffic shaping reduce wasted movement so each watt contributes to useful work. Runtime policies such as micro-batching, admission control, and stream prioritization can further lift efficiency if tail latency remains within target. The strongest gains come from iterative profiling loops that attribute energy to specific kernels, data paths, and idle intervals, then remove the dominant inefficiencies first. A useful explanation always ties observed symptom to a repeatable path where useful work was blocked, delayed, or diluted by overhead.

Use Sustained throughput per watt under SLA-constrained load, including memory and host-orchestration overhead. as an alarm, then anchor action using hard evidence such as Perf-per-watt optimization report with bottleneck ranking, intervention plan, and before-after operating points..

Precision policy is a system-level contract between quality, latency, and thermal limits. 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.