agent/tools/profile.sh

#!/bin/bash
# nsys/ncu wrapper that emits a DIAGNOSIS, not a report dump.
#
#   ./profile.sh nsys python3 bench.py            # is the time even in a kernel?
#   ./profile.sh ncu  python3 bench.py            # which resource is saturated?
#   KERNEL=my_kern ./profile.sh ncu python3 bench.py    # restrict to matching kernels (regex)
#
# ncu needs GPU performance counters. Run the container with --cap-add SYS_ADMIN, or have the host set
# NVreg_RestrictProfilingToAdminUsers=0. `ncu --version` succeeding proves nothing -- it never touches
# a counter. Without permission you get ERR_NVGPUCTRPERM.
set -uo pipefail
MODE=${1:-ncu}; shift

if [ "$MODE" = "nsys" ]; then
  O=/tmp/_nsys.$$
  nsys profile -o $O --force-overwrite true --trace=cuda,nvtx,osrt "$@" >/dev/null 2>&1
  echo "== per-kernel totals =="
  nsys stats --report cuda_gpu_kern_sum $O.nsys-rep 2>/dev/null | sed -n '/Time (%)/,$p' | head -14
  echo
  echo "Read this first: if the summed kernel time is far below wall time, you are HOST-BOUND --"
  echo "launch gaps, dispatch, or H2D/D2H. Fix that before opening ncu."
  echo "Report kept at $O.nsys-rep -- open the timeline for gaps and missing overlap."
  exit 0
fi

REP=/tmp/_ncu.$$; LOG=/tmp/_ncu.log.$$
ncu --target-processes all ${KERNEL:+--kernel-name regex:$KERNEL} --launch-skip 3 --launch-count 3 \
    --section SpeedOfLight --section MemoryWorkloadAnalysis \
    --section WarpStateStats --section Occupancy \
    --metrics sm__throughput.avg.pct_of_peak_sustained_elapsed,\
gpu__dram_throughput.avg.pct_of_peak_sustained_elapsed,\
l1tex__t_sectors_per_request.avg,\
l1tex__data_bank_conflicts_pipe_lsu_mem_shared.sum,\
sm__warps_active.avg.pct_of_peak_sustained_active,\
launch__registers_per_thread \
    -o $REP --force-overwrite "$@" >$LOG 2>&1

if grep -q ERR_NVGPUCTRPERM $LOG; then
  echo "ERR_NVGPUCTRPERM -- no access to GPU performance counters."
  echo "  fix: run the container with --cap-add SYS_ADMIN, or set"
  echo "       NVreg_RestrictProfilingToAdminUsers=0 on the host."
  exit 1
fi
if [ ! -f $REP.ncu-rep ]; then
  echo "ncu produced no report. Last lines:"; tail -5 $LOG; exit 1
fi

ncu -i $REP.ncu-rep --csv 2>/dev/null > /tmp/_ncu.csv.$$
python3 - /tmp/_ncu.csv.$$ <<'PY'
import csv, sys
rows = list(csv.DictReader(open(sys.argv[1])))
if not rows:
    print("no kernels matched."
          + (" Loosen or drop KERNEL=." if __import__("os").environ.get("KERNEL") else ""))
    raise SystemExit(1)
kern = rows[0].get("Kernel Name", "?")
def get(name):
    for r in rows:
        if r.get("Metric Name", "").strip() == name:
            try: return float(r["Metric Value"].replace(",", ""))
            except Exception: return None      # ncu prints 'n/a' for metrics it could not collect
    return None
sm   = get("sm__throughput.avg.pct_of_peak_sustained_elapsed")
dram = get("gpu__dram_throughput.avg.pct_of_peak_sustained_elapsed")
sect = get("l1tex__t_sectors_per_request.avg")
bank = get("l1tex__data_bank_conflicts_pipe_lsu_mem_shared.sum")
occ  = get("sm__warps_active.avg.pct_of_peak_sustained_active")
regs = get("launch__registers_per_thread")
f = lambda v, u="": "n/a" if v is None else f"{v:.1f}{u}"
print(f"kernel: {kern[:70]}")
print(f"SM {f(sm,'%')}   DRAM {f(dram,'%')}   occupancy {f(occ,'%')}   "
      f"sectors/req {f(sect)}   bank-conflicts {f(bank)}   regs/thread {f(regs)}")
print("\nDIAGNOSIS")
if sm is not None and dram is not None:
    if   sm > 60 and dram < 40: print("  COMPUTE-BOUND -> tensor cores, better instruction mix, less redundant work")
    elif dram > 60 and sm < 40: print("  BANDWIDTH-BOUND -> cut traffic, fuse passes, improve reuse")
    elif sm < 40 and dram < 40: print("  LATENCY-BOUND -> read WarpStateStats; more loads in flight (cp.async/TMA), more ILP")
    else:                       print("  MIXED -> attack whichever of SM/DRAM is higher first")
else:
    print("  SpeedOfLight metrics unavailable -- open the report by hand.")
if sect and sect > 4.5:  print(f"  UNCOALESCED: {sect:.1f} sectors/request (4 is ideal) -> fix layout/access pattern")
if bank:                 print(f"  SHARED-MEM BANK CONFLICTS: {bank:.0f} -> swizzle (do NOT pad 2-byte types)")
if occ and occ < 30:     print(f"  LOW OCCUPANCY {occ:.0f}% -> run tools/occupancy.py to find the limiter")
if regs and regs >= 168: print(f"  {regs:.0f} regs/thread -> spills likely; check SASS for LDL/STL")
print("\nReminder: never take a TIMING from a run under ncu -- it serializes and replays kernels.")
PY
echo "full report: ncu -i $REP.ncu-rep --page details"
rm -f /tmp/_ncu.csv.$$ $LOG