Inference Perf Bench

inference-perf-bench

Fast model loading (always-applied): when standing up a vLLM deploy, never load 100s-of-GB single-stream via s3fs FUSE (a GLM-5.1-sized model takes ~50 min that way. See docs/METHODOLOGY.md). Prefer, in order: a fast model-loading endpoint when reachable -> parallel multipart to local NVMe (server/tools/stage-model-parallel.py) -> runai_model_streamer (--load-format runai_streamer) -> tensorizer. Flag a slow load loudly: if effective rate < ~500 MB/s on a large model, STOP and switch. Details: server/docs/inference-fast-model-loading.md.

Purpose

Drive inference performance benchmarks against an in-cluster inference endpoint using NVIDIA's AIPerf tool and the replay-playback HuggingFace dataset of recorded multi-turn agentic-coding conversations (the dataset may be gated - confirm your HF token has access before starting). Runs from an in-cluster bench pod for accurate latency measurement. Supports concurrency sweeps, multi-model comparison, and server-side metric capture.

Steady-state window (throughput trap): drive num_prompts >= 2*c at each concurrency c (AIPerf/vllm bench serve measure throughput over the full run. Too few prompts make the window ramp/drain-dominated and undercount high-c throughput ~1.6-1.8x). Default sweeps use num_prompts=2*c (e.g. 128 @ c=64). See docs/METHODOLOGY.md trap 4.

The core benchmark loop is a standard 9-phase AIPerf workflow (Phase B below). This file does not belabor the per-phase mechanics. It adds project cross-references for the perf-baseline registry, perf-lake export, and evidence bundle scaffolding that turn a bench run into a durable, comparable result.

When to use

• Before promoting a new model to staging or prod - validate performance on dev before promotion.
• After vllmArgs tuning, vLLM version bumps, or KV cache dtype changes - re-measure to confirm no regression.
• Side-by-side comparison of two model configs (NVFP4 vs FP8, EAGLE3 on/off, different tensor-parallel sizes, etc.).

Do not use this skill for:

• Training perf measurement (step-time / MFU / scaling-efficiency) - out of scope for this skill, which measures serving-side TTFT / ITL / throughput.
• NCCL collective-bandwidth measurement - use the upstream nccl-tests suite.
• Quality / accuracy evaluation (GPQA, MMLU-Pro, Terminal-Bench, SWE-Bench) - use inference-model-eval.
• Model deployment / promotion itself - creating or updating standing deployments is a platform operation outside this plugin's scope.

Example prompts

• "Run perf-bench on the kimi-k25 dev deployment with concurrency sweep 1,4,8,16,32."
• "Benchmark throughput of glm-5-fp8 against the 2025_07 split."
• "Compare NVFP4 vs FP8 on the deepseek-v4 dev pods using AIPerf."
• "TTFT P95 sweep on the new minimax-m2.7 deployment."
• /run-perf-bench --model kimi-k25 --concurrency 16 --split 2025_07
• /inference-perf-bench --models kimi-k25,glm-5-fp8 --concurrency 1,4,8,16,32

Prerequisites

Standard bench prerequisites plus the project's provenance contract:

1. HF_TOKEN - a HuggingFace read token with access to the replay-playback dataset.
2. kubectl context for a dev cluster - run kubectl config use-context <ctx> before invoking.
3. Namespace - the namespace where the bench pod (e.g. my-perf-bench) lands.
4. PROFILE_AND_OPTIMIZE_REPO_ROOT - set by the bundled MCP server at install time. The workflow writes the result bundle under ${PROFILE_AND_OPTIMIZE_REPO_ROOT}/experiments/artifacts/inference-perf-bench/<UTC-ts>/.

Interaction style

Iterative - the 9-phase runbook pauses naturally at each phase. After Phase 5 (the actual benchmark run) completes, hand off to the bridge skills below before deleting the bench pod.

Workflow

Phase A: scaffold an evidence bundle

Optional but recommended. Use evidence-bundle-init:

/evidence-bundle-init --family inference-perf-bench --intent "perf-bench on <model> at concurrency <C>"

This creates experiments/artifacts/inference-perf-bench/<run-id>/ with SOURCE.md, summary.md, commands/. Every shell command in the 9-phase workflow can then be captured as a four-file tuple under commands/ for the reproducibility-grade-evidence rule (server/AGENTS.md).

Phase A.25: write the pre-bench estimate

Before choosing a broad concurrency sweep, apply inference-performance-hints. Record a DRAFT estimate ledger in the bundle: expected weight/KV, compute, collective, launch/host, and queueing terms, their sources, and which costs overlap. Use it to choose the smallest sweep that crosses the expected latency/throughput knee and to name the server counters or profile that would refute the estimate.

The estimate does not replace c=1, knee, and saturation measurements. It prevents an unexplained grid from becoming the experiment plan.

Phase A.5: pre-bench - quiet Slurm (Slurm-on-K8s clusters only)

If the inference deployment runs on a Slurm-on-K8s cluster where slurmd worker pods (slurm-b200-*, etc.) co-host the vLLM replicas on the same GPU nodes, drain the Slurm partition for the bench window so a co-tenant Slurm job can't steal CPU, host RAM, /dev/shm, PCIe BW, or IB fabric capacity from the inference pod mid-measurement. Use the slurm_quiet_window MCP verb:

mcp__profile_and_optimize__slurm_quiet_window with:
  args: ["--nodes", "<comma-list of slurm-* worker pod names>",
         "--cmd", "<your Phase B/C bench cmd>",
         "--bundle", "<your bundle>/slurm-quiet-window-<UTC>",
         "--json"]
  i_understand_this_substitutes_nodes: true

The orchestrator drains, runs your bench cmd, and ALWAYS resumes via a Python try/finally so a Ctrl-C, exception, or non-zero bench-cmd exit cannot leave the partition stuck in drained. Skip this phase when the cluster has dedicated inference nodes (no Slurm-on-K8s co-tenancy) or when the operator has already drained Slurm by hand.

Phase B: run the 9-phase benchmark loop

The phases execute in order: (1) Dataset Check, (2) Bench Pod Setup, (3) Identify Target Endpoints, (4) Capture Pre-Run Server Metrics, (5) Run Benchmark, (6) Monitor, (7) Capture Post-Run Server Metrics, (8) Download Results, (9) Report.

The four canonical vLLM Prometheus metrics captured in Phases 4 + 7 are also the canonical metric set prometheus-anchored-query exposes as a worked example: vllm:prefix_cache_hit_rate, vllm:gpu_cache_usage_perc, vllm:num_requests_running, vllm:avg_generation_throughput_toks_per_s.

Phase C: register a baseline

After Phase 9 (Report), the operator has a perf-bench-report-<YYYY-MM-DD>.md plus per-concurrency aiperf logs. Register the result as a baseline for future regression diffs:

/inference-perf-baseline-bridge record \
  --model <model> \
  --source experiments/artifacts/inference-perf-bench/<run-id>/

See inference-perf-baseline-bridge for the full contract.

Phase D: land the result in the perf-lake (MANDATORY)

Per the server/AGENTS.md "Experiment Isolation & Traceability" rule, a measurement is not a result until it lands in the perf-lake with Speed-of-Light rooflines. The canonical path is the perftunereport pipeline (see inference-perf-tune-report), keyed by campaign=<id> where <id> is this bundle's run-id:

perftunereport campaign_init  --config <campaign>.yaml      # campaign id = run-id; set focus: latency|throughput|mixed
perftunereport cell_run ...   --i-understand-this-submits-jobs
perftunereport atlas_aggregate --campaign <id>
perftunereport dcgm_correlate  --campaign <id> --cell-id <cell> --frozen-yaml <dcgm-frozen>.yaml  # raises sol_rigor to L3 (pages 6/6b)
perftunereport import_roofline_sweep --campaign <id> --bundle <roofline-out> --hardware GB300 --tensor-parallel <tp> --cache-mode cold  # page 7
perftunereport report_render   --campaign <id>              # SoL roofline pages; sets sol_complete + sol_rigor
perftunereport publish_to_lake --campaign <id> --i-understand-this-publishes-externally  # atlas_v1 + campaign_v1 parquet

Always-on prefill/decode roofline. Before publish, capture an operator-provided decode-concurrency and prefill-ISL sweep with per-cell DCGM metrics. Run import_roofline_sweep so the campaign carries page 7 (per-GPU roofline + HBM%/tensor%/SM%-vs-concurrency - the "what C maxes the TFLOPs / is decode

=75% HBM / which sharding degree" answers. Per-(c,ISL) DCGM lands in atlas_v1.extra_json). Sweep every candidate config (TP / KV-dtype) so page 7 overlays them. See inference-perf-tune-report Phase D3.

Strict publish with focus + sol_rigor. Every complete run publishes a sol_complete roofline and records focus (set it in the campaign YAML) + sol_rigor (L4 ncu | L3 DCGM | L1 zymtrace-proxy | none). The DCGM + zymtrace capture below RAISES sol_rigor toward L3/L4 - it is not a publish gate. publish_to_lake is strict by default and refuses a latency-bound, proxy, or dcgm_grounded=false run that misses required evidence. Use --no-strict only for an intentional-gap publish, which records and warns on the gap. Still capture DCGM (SM/DRAM/tensor/GR + NVLINK bytes) concurrently with the bench window and fold it in via dcgm_correlate (or the inference-dcgm-correlate skill) for a tighter (L3) roofline.

This pipeline records gaps loudly instead of leaving silent blanks: import_perf_bench prints a WARNING: for any cell that imports as STATUS_FULL but lacks Median TTFT (ms) / Request throughput (req/s) (such a cell produces no scatter point), atlas_aggregate warns on 0 plot-ready / full-but-unplottable cells, report_render records every omitted SoL page (why + how-to-fix) on a completeness page + report_status.json. Strict publish refuses the gap. An explicit --no-strict publish records it on the lake row. If a cell's bench output is missing those lines, re-run the bench so it prints them, then re-import + re-aggregate + re-render.

Safety

• Read-only on the cluster except for the bench pod. The workflow creates and (in Phase Cleanup) destroys a single bench pod (e.g. my-perf-bench) via kubectl run / kubectl delete. No other cluster mutation.
• No public-gateway traffic by default. Phase 5 runs against the cluster-internal service DNS, never a public gateway - a public gateway adds variable cross-region overhead that contaminates measurements (dev-vs-prod throughput skews of 3x have been traced to exactly this).
• Bench pod cleanup is required. The Cleanup step (kubectl delete pod my-perf-bench) MUST run before the evidence bundle is finalized. Orphan bench pods consume cluster capacity for hours.
• No credential commit. HF_TOKEN and any provider API keys stay in env vars. Never written into the evidence bundle's SOURCE.md or commit history.

Experiment isolation & traceability (mandatory)

Per the server/AGENTS.md "Experiment Isolation & Traceability" rule (and docs/METHODOLOGY.md):

• Any disposable serve/bench deployment this workflow creates MUST use experiment-unique names derived from the run-id and carry the label experiment=<id-slug>. NEVER reuse standing/platform/migration names (standing deploys, shared *-cache PVCs, anything labeled migration=*). Cluster-scoped PV names are global - a collision silently breaks another owner's PVC.
• Tear down by label (kubectl delete deploy,pod,pvc,secret -l experiment=<id-slug>). Pre-clear the attacher finalizer on Retain experiment PVs before deleting. Verify standing/migration objects are untouched + Ready afterward.
• DCGM + zymtrace capture is required during the Phase 5 bench window (DCGM via the Prometheus MCP PromQL for the window+node. Zymtrace via the always-on DaemonSet flamegraph for the window+node) so the perf-lake roofline pages render. zymtrace flushes to ClickHouse asynchronously, so an empty L1 right after the window is ingest lag, not absence -- wait + requery for the freshest data (see server/docs/zymtrace-query-hygiene.md). Record the created object names + perf-lake campaign=<id> in the bundle SOURCE.md.

Full-context reporting (no bare numbers)

Per the methodology canon "Every performance number carries its full context (no bare numbers)" (docs/METHODOLOGY.md): every number this skill emits MUST carry its full measurement-context descriptor, and every comparison MUST be matched on it. A bare tok/s / TPOT / BW / %SoL / speedup is a defect - it cannot set a default, ship a config, or appear in a report.

• Identity: model (+HF path), hardware (exact ceiling token GB300/B200), quant, kv-cache dtype.
• Parallelism: TP, DP (replicas), PP, EP, parallel_strategy.
• Serving cfg: max-num-seqs, max-num-batched-tokens, gpu-memory-utilization, max-model-len, cudagraph_mode/enforce_eager, async_scheduling, prefix-caching.
• Workload: dataset, ISL/OSL (or mean in/out tokens), concurrency, num-prompts.
• Regime: warm vs cold. Latency vs throughput tier.
• Stack: image/vllm commit, bench backend, serving engine.
• Grounding: %SoL (+ ceiling key from configs/sol-ceilings.yaml - never inline a peak), sol_rigor (L1-L4), trials n (mean±std), same-node, baseline named.
• Per-number exact shape (no smoothing): when reporting more than one number, keep EACH with its own exact shape (ISL/OSL, concurrency, dataset, regime) - never normalize a set to one uniform descriptor that hides per-point variation (e.g. c=1 @ ISL1024/OSL256 + c=64 @ ISL4096/OSL512, NOT one shared "random").

Every result table this skill produces MUST carry a %SoL column alongside the absolute throughput / latency numbers. Per the server/AGENTS.md "Speed-of-light framing" section:

• Workload-level: peak output_tps_per_gpu compared to the HBM-bandwidth ceiling (b200_sm100.hbm3e_tbps = 8.0 TB/s ÷ per-token footprint). Per-token footprint depends on model, e.g. GLM-5.1 NVFP4 at ISL=4096 / OSL=512 is ~7 GB/token.
• Source of all peak numbers: configs/sol-ceilings.yaml
• cite by key path (b200_sm100.hbm3e_tbps, etc.). Never inline.
• Per-run sol-summary doc lives at <campaign>/sol-summary.md and carries the workload-level %SoL row. The perf-report PDF page 4 picks it up automatically when zymtrace per-category data is also present in the bundle.

Next lever / BREAKTHROUGH (Grind Mandate)

If this skill emits a measured result, its output MUST end by naming the next perf lever, its expected unlock (direction + rough magnitude), and the gate that proves/refutes it, per "The Grind Mandate" (server/AGENTS.md + docs/METHODOLOGY.md). A measured win is the new floor, not the finish -- so do everything we can to find the next BREAKTHROUGH: the highest-EV unlock toward Speed-of-Light (a new champion / kernel / router / quant / parallelism / spec-decode win, or an unblocked stack), not just the next micro-lever. Rank the candidate breakthrough levers by value x cost (the GRIND FRONTIER, perftunereport value_view), pursue the top, bank the rest with evidence. Record WHY a refuted lever loses, update the standing frontier in the active bundle's HANDOFF.md. Never conclude "exhausted/optimal/done" without an explicit next-lever frontier (an empty frontier AND a documented SoL wall only). Delete this section ONLY if the skill produces no measurements.

Verdict rigor (DRAFT vs VERDICT)

Per server/AGENTS.md "Verdict rigor: DRAFT vs VERDICT", tier every bench number. A single sweep is a DRAFT. Promote to a VERDICT only when variance-controlled (same-node, >=3 trials, mean +/- std), metric-isolated (median TPOT/ITL for decode-latency claims - output tok/s at small num_prompts is TTFT-dominated, NOT decode), and against a production-representative baseline (cudagraph-on, shipped backend. Never an eager strawman). Mark the campaign verdict_tier accordingly. The perf-lake writer gates verdict_tier=verdict on this provenance.

Quant-format / serve-backend claims are a MATRIX, not a single cell (per server/AGENTS.md "Validate the matrix, never generalize from one cell" + docs/METHODOLOGY.md). When A/B-ing quant formats or serve backends (NVFP4 marlin vs cutlass, FP8 compressed-tensors, ...), a single (backend, concurrency) point is NEVER a universal verdict -- the winner is concurrency-dependent (e.g. on Qwen3: FP8 wins c1 latency, NVFP4-marlin the c16 knee, NVFP4-cutlass throughput at c64-256. No universal best). MANDATORY for such a verdict: run the serve-backend x concurrency matrix same-node (one pod, all backends, 3 trials) and aggregate the cells. Root-cause any failed/degenerate cell by reading the (EngineCore pid=...) worker traceback instead of assuming the backend is blocked. Report the winner PER concurrency regime.

Source-of-truth references

• Pair: ai-bench (colloquial alias of this skill), inference-model-eval (quality-side counterpart).
• Bridge: inference-perf-baseline-bridge.
• server/AGENTS.md - fail-fast + provenance rules.