Profile Querying

Run SQL queries against NKI kernel profile data using neuron-explorer view. This ingests NEFF+NTFF into parquet and exposes a DuckDB-backed API server on localhost. No deployment, no remote service — just the CLI and curl.

For more advanced analysis, use python on parquet to compute performance bounds and investigate precise inefficiencies within arbitrary execution intervals.

What you need: A compiled NEFF file and a captured NTFF trace file. These come from /neuron-nki-profiling or from running a kernel with the right env vars and neuron-explorer capture.

Quick Start

# Ingest and start API server (no web UI)
neuron-explorer view \
  -n ./kernel.neff \
  -s ./profile.ntff \
  --data-path ~/.local/share/neuron-profile \
  --display-name my-kernel \
  --disable-ui &

# Wait for server
sleep 10

# Query
curl -s -X POST http://localhost:3002/api/v1/db/my-kernel/_search \
  -H 'Content-Type: application/json' \
  -d '{"type":"databaseExplorerQuery","tableName":"Summary","query":"SELECT total_time, mfu_estimated_percent, tensor_engine_active_time_percent, dma_active_time_percent FROM Summary"}'

That's it. Ingest, serve, query.

Prerequisites

• neuron-explorer installed (comes with AL2023 DLAMI or aws-neuronx-tools)
• NEFF file (compiled kernel binary) + NTFF file (execution trace)

Check availability:

which neuron-explorer && neuron-explorer --version

If not found, check /opt/aws/neuron/bin/neuron-explorer.

Step-by-Step Workflow

Step 0: Check Profile Quality (Re-profile if Needed)

Note: This step is specific to NKI kernel development. If you are querying a profile that was generated outside of an NKI workflow, skip to Step 1.

Disclaimer: Query results are only as good as the profile. If the NEFF/NTFF were captured without the right env vars, key tables (DmaPacket, DmaPacketAggregated) may be empty and source-level attribution will be missing.

Check whether the profile has the data you need:

# After ingesting (Step 2), check for DMA packet data
curl -s -X POST http://localhost:3002/api/v1/db/${PROFILE_NAME}/_search \
  -H 'Content-Type: application/json' \
  -d '{"type":"databaseExplorerQuery","tableName":"DmaPacket","query":"SELECT COUNT(*) as cnt FROM DmaPacket"}'

If cnt is 0 or the table is missing, the profile was captured without DGE notifications. If bir_debug_info_source_location is NULL on all Instruction rows, the NEFF was compiled without debug info.

To re-profile for best results, set these env vars in the kernel script before any neuron imports, then re-run and re-capture:

import os
os.environ["XLA_IR_DEBUG"] = "1"
os.environ["XLA_HLO_DEBUG"] = "1"
os.environ["NEURON_FRAMEWORK_DEBUG"] = "1"
os.environ["NEURON_RT_VISIBLE_CORES"] = ... # Restrict available cores when running experiments in parallel.
os.environ["NEURON_RT_INSPECT_ENABLE"] = "1"
os.environ["NEURON_RT_INSPECT_DEVICE_PROFILE"] = "1"
os.environ["NEURON_RT_INSPECT_SYSTEM_PROFILE"] = "0"
os.environ["NEURON_RT_INSPECT_OUTPUT_DIR"] = ... # This is for the NEFF generation if needed. NTFF will go to the -s capture path in the next command. 

Then re-capture with DGE notifications enabled:

NEFF_PATH=$(find ./output -name "*.neff" | head -1)
NEURON_RT_ENABLE_DGE_NOTIFICATIONS=1 neuron-explorer capture \
  -n "$NEFF_PATH" \
  -s profile.ntff \
  --profile-nth-exec=2

With --profile-nth-exec=2, the output file is profile_exec_2.ntff (not profile.ntff), written to the directory specified by the -s flag.

If the existing profile has the data you need, skip this step entirely.

Another thing to look out for is running torch functions on device like randomnly generating inputs. This will be fused into the kernel execution and obfuscate it's profile. Move those commands off device if you want to isolate kernel execution.

Step 1: Ingest and Start Server

If you want to run SQL queries against the Neuron Explorer DuckDB engine, use the view command with --disable-ui to start the server.

Set variables:

NEFF_PATH=<resolved neff path>
NTFF_PATH=<resolved ntff path>
PROFILE_NAME=<descriptive name, e.g. "my-matmul">
NE_DATA_PATH=~/.local/share/neuron-profile

Check if the neuron-explorer server is already running:

curl -s http://localhost:3002/api/v1/health

If the server is already running or if you are running python directly on the parquet, use --ingest-only in the following command instead of --disable-ui.

neuron-explorer view \
  -n "$NEFF_PATH" \
  -s "$NTFF_PATH" \
  --data-path "$NE_DATA_PATH" \
  --display-name "$PROFILE_NAME" \
  --disable-ui \
  > /tmp/neuron-explorer-${PROFILE_NAME}.log 2>&1 &
NE_PID=$!
echo "neuron-explorer started (PID: $NE_PID), waiting for API..."

The command may fail on an conflicting port from the existing server but the ingestion may have still succeeded. If so, check for Processing for ... is complete before the error message or rerun with --ingest-only.

Wait for API:

for i in $(seq 1 60); do
  if curl -s http://localhost:3002/api/v1/health 2>/dev/null | grep -q healthy; then
    echo "API server ready"
    break
  fi
  sleep 1
done

Step 2: Read the Schema

Before writing any queries, check the table docs in references/schema/ for interpretive guidance on the most commonly used tables. For any table not covered there, query its schema directly from neuron-explorer using the following commands:

curl -s -X POST http://localhost:3002/api/v1/db/${PROFILE_NAME}/_search \
  -H 'Content-Type: application/json' \
  -d '{"type":"tableSchema","tableName":"Instruction"}' | python3 -m json.tool

List all available tables:

curl -s -X POST http://localhost:3002/api/v1/db/${PROFILE_NAME}/_search \
  -H 'Content-Type: application/json' \
  -d '{"type": "listDbFiles"}' | python3 -m json.tool

Step 3a: Execute SQL Queries

Use databaseExplorerQuery for arbitrary SQL (SELECT only).

Summary metrics — which engine is the bottleneck?

curl -s -X POST http://localhost:3002/api/v1/db/${PROFILE_NAME}/_search \
  -H 'Content-Type: application/json' \
  -d '{"type":"databaseExplorerQuery","tableName":"Summary","query":"SELECT total_time, mfu_estimated_percent, tensor_engine_active_time_percent, vector_engine_active_time_percent, dma_active_time_percent, hbm_read_bytes, hbm_write_bytes FROM Summary"}' | python3 -m json.tool

Instruction breakdown — what is each engine doing and waiting on?

curl -s -X POST http://localhost:3002/api/v1/db/${PROFILE_NAME}/_search \
  -H 'Content-Type: application/json' \
  -d '{"type":"databaseExplorerQuery","tableName":"Instruction","query":"SELECT engine, opcode, COUNT(*) as cnt, SUM(duration_ns) as total_dur_ns, SUM(evt_wait_time_ns) as total_evt_wait_ns FROM Instruction GROUP BY engine, opcode ORDER BY total_dur_ns DESC"}' | python3 -m json.tool

NKI source line hotspots — which lines of the kernel are slowest?

curl -s -X POST http://localhost:3002/api/v1/db/${PROFILE_NAME}/_search \
  -H 'Content-Type: application/json' \
  -d '{"type":"databaseExplorerQuery","tableName":"Instruction","query":"SELECT bir_debug_info_source_location, engine, opcode, COUNT(*) as cnt, SUM(duration_ns) as total_dur_ns FROM Instruction WHERE bir_debug_info_source_location IS NOT NULL GROUP BY bir_debug_info_source_location, engine, opcode ORDER BY total_dur_ns DESC LIMIT 10"}' | python3 -m json.tool

Step 3b: Python DuckDB on Parquet

For SQL queries without the API server, use DuckDB's Python bindings directly on the parquet files. After ingestion (Step 1), the data lives at:

<data-path>/profiles/global/<display-name>@latest/<Table>.parquet

import duckdb

NE_DATA_PATH = "~/.local/share/neuron-profile"
PROFILE = "my-kernel"
PARQUET_DIR = f"{NE_DATA_PATH}/profiles/global/{PROFILE}@latest"

con = duckdb.connect()

# Load tables directly from parquet
con.execute(f"CREATE VIEW Instruction AS SELECT * FROM '{PARQUET_DIR}/Instruction.parquet'")
con.execute(f"CREATE VIEW DmaPacket AS SELECT * FROM '{PARQUET_DIR}/DmaPacket.parquet'")

# Example: measure LDWEIGHTS/MATMUL temporal overlap
result = con.execute("""
    SELECT
        CASE WHEN lw.end_ts <= mm.start_ts THEN 'lw_before'
             WHEN lw.start_ts >= mm.end_ts THEN 'lw_after'
             ELSE 'overlap' END as rel,
        COUNT(*) as cnt
    FROM Instruction mm
    JOIN Instruction lw ON mm.bir_id = lw.bir_id
    WHERE mm.opcode = 'MATMUL' AND lw.opcode = 'LDWEIGHTS'
      AND mm.tensor_instruction_type = 'REGULAR'
      AND lw.tensor_instruction_type = 'REGULAR'
    GROUP BY rel
""").fetchdf()
print(result)

Step 3c: Pandas on Parquet

For analyses that require Python computation — interval merges, custom metrics, numpy operations, or cross-table joins with arbitrary logic — load the parquet files directly with pandas.

import pandas as pd, numpy as np, os

NE = os.path.expanduser("~/.local/share/neuron-profile/profiles/global")
profile = "my-kernel"
d = f"{NE}/{profile}@latest"

# Load tables
summary  = pd.read_parquet(f"{d}/Summary.parquet").iloc[0]
inst     = pd.read_parquet(f"{d}/Instruction.parquet")
active   = pd.read_parquet(f"{d}/ActiveTime.parquet")
metadata = pd.read_parquet(f"{d}/Metadata.parquet").iloc[0]
dma_pkts = pd.read_parquet(f"{d}/DmaPacket.parquet")
dma_agg  = pd.read_parquet(f"{d}/DmaPacketAggregated.parquet")
tensors  = pd.read_parquet(f"{d}/TensorInfo.parquet")
flow     = pd.read_parquet(f"{d}/Flow.parquet")

This is the approach used by the performance bounds computation and all investigations in the Profile Analysis workflow.

Step 4: Interpret Results

Only claim what the data shows. Profile data is precise but narrow — it tells you what happened, not always why.

• Don't diagnose from single metrics. A query result is a measurement, not a conclusion. Low utilization, high wait times, or large byte counts need context from other tables before they mean anything.
• Don't assume field names mean what they sound like. Some fields are unpopulated or misleading for NKI kernels. Check references/schema/ before building conclusions on a field you haven't validated.
• Don't compare engines without interval merging. Instructions overlap within an engine (pipelining) and across engines (parallelism). Raw sums from the Instruction table overstate wall-clock time. Use ActiveTime for wall-clock comparisons.
• Don't skip the data quality check. If DmaPacketAggregated is missing or bir_debug_info_source_location is mostly NULL, the query results are incomplete — re-profile before interpreting.

Step 8: Cleanup

kill $NE_PID 2>/dev/null

Profile Analysis

If you are asked for analysis of the profile, follow this workflow. All logic — bound definitions, gap interpretation, and investigation selection — lives in performance-bounds.md.

1. Calculate bounds

Follow the "The bounds" section of performance-bounds.md to compute all three families (memory, compute, pipeline). These require Python on parquet (Step 3c).

2. Identify the dominant gaps

Follow "Reading the gaps" in performance-bounds.md. Compute each consecutive-pair gap within the memory and compute families, plus the pipeline gap. Report all gaps and their sizes relative to total_time.

3. Run investigations

Follow "From bounds to investigations" in performance-bounds.md. Use the bottleneck engine and gap sizes to select which investigation groups to run. Each investigation has a Step 1 (detect and quantify) and Step 2 (localize to NKI source lines). Run all relevant investigations — a kernel typically has multiple active inefficiencies.

4. Report

Present a single summary:

• Bounds table: all bounds with values and the gap between each pair. Also report each engine's total time pointing out the largest one(s) as the bottleneck(s). If neither DMA nor Tensor Engine is the bottleneck, explain which engine is the bottleneck and that supporting it is still WIP.
• Per-investigation findings: gap size, source lines responsible, and their contributions. Include investigations that found nothing so the analysis is visibly complete.

Order the presented inefficiencies and investigation findings according to it's relevance to the bottlenecks and the measured gaps.

4. Follow up (After an optimization step/attempt)

After an optimization step or attempt, investigate the new profile to identify exactly what improved or regressed. Follow the full process and present a side by side report of all of the bounds and engine times as well as the new investigation findings. Highlight changes but do not over-interpret, only relay what the evidence shows. Static code analysis is faulty, you will be tempted to over-intepret the causes and effects, DON'T (unless EXPLICITELY) asked to.

Worked Examples

For end-to-end examples of profile-guided optimization, see:

Multi-Kernel Querying

All profiles sharing the same --data-path are served by one server. Each profile is queried by its --display-name.

NE_DATA_PATH=~/.local/share/neuron-profile

neuron-explorer view -n $NEFF_A -s $NTFF_A --data-path "$NE_DATA_PATH" --display-name kernel-a --disable-ui &
neuron-explorer view -n $NEFF_B -s $NTFF_B --data-path "$NE_DATA_PATH" --display-name kernel-b --disable-ui &

# Query either through same server
curl localhost:3002/api/v1/db/kernel-a/_search ...
curl localhost:3002/api/v1/db/kernel-b/_search ...

For batch ingestion without a server, use --ingest-only instead of --disable-ui. It writes parquet and exits. Any future server on the same data-path discovers the ingested profiles.

Parquet lands at <data-path>/profiles/global/<display-name>@latest/.

Port Conflicts

If port 3002 is already in use, ingestion still succeeds — parquet is written to disk before the server attempts to bind.

lsof -i :3002 | head -5

• If it's neuron-explorer on the same data-path: reuse it — it discovers newly ingested profiles automatically.
• If it's something else: use --api-server-port 4002 (or any free port).

Important Notes

• Use neuron-explorer not neuron-profile for all capture and view commands.
• DGE notifications are required for DMA packet-level tables (DmaPacket, DmaPacketAggregated). Set NEURON_RT_ENABLE_DGE_NOTIFICATIONS=1 in the environment before neuron-explorer capture. Do NOT rely on the CLI flag — use the env var directly.
• Always pass --data-path explicitly.
• The API server binds to localhost only.
• Only SELECT queries are supported via the API.
• --display-name becomes the profile identifier in API URLs.
• --disable-ui skips the web UI (port 3001) but starts the API server (port 3002).
• --ingest-only writes parquet and exits — no server at all.

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