127 lines
4.2 KiB
Python
127 lines
4.2 KiB
Python
"""CPU topology detection (physical cores, not hyperthreads).
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Reads /sys/devices/system/cpu/* and falls back to ``lscpu``. Pure
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stdlib; no internal package dependencies.
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Extracted from ``open-transcode.v3.py`` (QA item v4-03 — package split).
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This is a pure code-organization refactor; behavior is identical to v3.
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"""
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import os
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import shutil
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import subprocess
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import sys
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from dataclasses import dataclass
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from pathlib import Path
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# ──────────────────────────────────────────────
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# CPU TOPOLOGY (physical cores, not hyperthreads)
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# ──────────────────────────────────────────────
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@dataclass
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class CpuTopology:
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physical_cores: int
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logical_threads: int
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threads_per_core: int
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model_name: str
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def _read_sysfs_cores() -> (tuple[int, int]) | None:
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"""
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Read /sys/devices/system/cpu/cpu*/topology/ to count unique
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(physical_package_id, core_id) pairs — i.e. physical cores.
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Returns (physical_cores, logical_threads) or None.
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"""
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cpu_base = Path("/sys/devices/system/cpu")
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if not cpu_base.exists():
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return None
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unique_cores: set[tuple[str, str]] = set()
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logical = 0
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for cpu_dir in sorted(cpu_base.glob("cpu[0-9]*")):
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core_id_file = cpu_dir / "topology" / "core_id"
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pkg_id_file = cpu_dir / "topology" / "physical_package_id"
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if core_id_file.exists() and pkg_id_file.exists():
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try:
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pkg = pkg_id_file.read_text().strip()
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core = core_id_file.read_text().strip()
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unique_cores.add((pkg, core))
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logical += 1
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except (OSError, ValueError):
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# OSError: file vanished/permission; ValueError: UnicodeDecodeError
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pass
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if unique_cores and logical:
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return (len(unique_cores), logical)
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return None
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def _read_lscpu_cores() -> (tuple[int, int]) | None:
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"""Fallback: parse lscpu -p=CORE,SOCKET for unique physical cores."""
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if not shutil.which("lscpu"):
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return None
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try:
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res = subprocess.run(
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["lscpu", "-p=CORE,SOCKET"],
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capture_output=True, text=True, timeout=5,
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)
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lines = [l.strip() for l in res.stdout.strip().splitlines() if l.strip() and not l.startswith("#")]
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if lines:
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unique = set(lines)
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return (len(unique), len(lines))
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except (OSError, subprocess.SubprocessError):
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pass
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return None
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def detect_cpu_topology() -> CpuTopology:
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"""
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Detect physical CPU topology. Prefers /sys filesystem, falls back
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to lscpu, then estimates from os.cpu_count().
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"""
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logical = os.cpu_count() or 1
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physical = logical
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# Try /sys first (most reliable)
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result = _read_sysfs_cores()
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if result:
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physical, logical = result
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else:
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# Try lscpu
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result = _read_lscpu_cores()
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if result:
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physical, logical = result
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else:
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# Estimate: assume 2 threads/core if cpu_count > 2 and is even
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if logical > 2 and logical % 2 == 0:
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physical = logical // 2
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tpc = logical // physical if physical > 0 else 1
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# Try to get CPU model name
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model = "Unknown CPU"
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model_file = Path("/proc/cpuinfo")
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if model_file.exists():
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for line in model_file.read_text(errors="replace").splitlines():
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if line.startswith("model name"):
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model = line.split(":", 1)[1].strip()
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break
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else:
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# Non-x86 / non-Linux: try lscpu
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if shutil.which("lscpu"):
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try:
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res = subprocess.run(["lscpu"], capture_output=True, text=True, timeout=5)
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for line in res.stdout.splitlines():
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if "Model name" in line:
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model = line.split(":", 1)[1].strip()
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break
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except (OSError, subprocess.SubprocessError):
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pass
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return CpuTopology(
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physical_cores=physical,
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logical_threads=logical,
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threads_per_core=tpc,
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model_name=model,
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)
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