Martino Ferrari
77 lines
2.5 KiB
Python
77 lines
2.5 KiB
Python
#!/usr/bin/env python3
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"""
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proc_perf.py — Snapshot a live process's CPU time and peak memory from /proc.
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Usage: proc_perf.py <pid> <label> <out.json>
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Reads /proc/<pid>/stat (utime+stime, in clock ticks) and /proc/<pid>/status
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(VmHWM = peak resident set, VmRSS = current) *while the process is alive* — peak
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RSS is only legible before the process exits, so the orchestrator calls this just
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before tearing the stack down. Emits a small JSON record:
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{"label": ..., "avail": true, "cpu_s": float, "peak_rss_kb": int,
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"rss_kb": int, "threads": int}
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If the process is already gone, writes {"label": ..., "avail": false}.
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"""
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import json
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import os
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import sys
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def _clk_tck():
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try:
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return os.sysconf("SC_CLK_TCK") or 100
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except (ValueError, OSError):
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return 100
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def snapshot(pid):
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stat_p = f"/proc/{pid}/stat"
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status_p = f"/proc/{pid}/status"
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if not os.path.exists(stat_p):
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return {"avail": False}
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try:
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with open(stat_p) as f:
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raw = f.read()
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# The comm field is parenthesised and may contain spaces/parens, so split
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# on the final ')': everything after it is space-separated, with state as
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# the first token. utime/stime are overall fields 14/15 → indices 11/12
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# of the post-')' tokens (pid + comm consumed before the split).
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after = raw[raw.rindex(")") + 1:].split()
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utime = int(after[11])
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stime = int(after[12])
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cpu_s = (utime + stime) / float(_clk_tck())
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rec: dict = {"avail": True, "cpu_s": cpu_s}
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with open(status_p) as f:
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for line in f:
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if line.startswith("VmHWM:"):
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rec["peak_rss_kb"] = int(line.split()[1])
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elif line.startswith("VmRSS:"):
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rec["rss_kb"] = int(line.split()[1])
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elif line.startswith("Threads:"):
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rec["threads"] = int(line.split()[1])
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return rec
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except (OSError, ValueError, IndexError):
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return {"avail": False}
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def main():
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if len(sys.argv) != 4:
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print("usage: proc_perf.py <pid> <label> <out.json>", file=sys.stderr)
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sys.exit(2)
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pid, label, out = sys.argv[1], sys.argv[2], sys.argv[3]
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rec = snapshot(pid)
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rec["label"] = label
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with open(out, "w") as f:
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json.dump(rec, f)
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if rec.get("avail"):
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print(f"perf {label}: cpu={rec.get('cpu_s', 0):.2f}s "
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f"peakRSS={rec.get('peak_rss_kb', 0)/1024:.1f}MB")
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else:
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print(f"perf {label}: unavailable (process gone)")
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if __name__ == "__main__":
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main()
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