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#!/usr/bin/env python3
# SPDX-License-Identifier: GPL-2.0
"""Calculate CPI from perf stat data or live."""
from __future__ import annotations
import argparse
import os
import signal
import sys
import time
from typing import Any, Optional
import perf
class StatCpiAnalyzer:
"""Accumulates cycles and instructions and calculates CPI."""
def __init__(self, args: argparse.Namespace) -> None:
self.args = args
self.data: dict[str, float] = {}
self.prev_data: dict[str, tuple[int, int, int]] = {}
self.recorded_pairs: set[tuple[int, int]] = set()
def get_key(self, event: str, cpu: int, thread: int) -> str:
"""Get key for data dictionary."""
return f"{event}-{cpu}-{thread}"
def store_key(self, cpu: int, thread: int) -> None:
"""Store CPU and thread IDs."""
self.recorded_pairs.add((cpu, thread))
def store(self, event: str, cpu: int, thread: int,
counts: tuple[int, int, int], is_delta: bool = False,
raw_name: Optional[str] = None) -> None:
"""Store counter values, computing difference from previous
absolute values if not already deltas."""
self.store_key(cpu, thread)
key = self.get_key(event, cpu, thread)
prev_key = self.get_key(raw_name or event, cpu, thread)
val, ena, run = counts
if is_delta:
# counts are already deltas
cur_val = val
cur_ena = ena
cur_run = run
else:
if prev_key in self.prev_data:
prev_val, prev_ena, prev_run = self.prev_data[prev_key]
cur_val = val - prev_val
cur_ena = ena - prev_ena
cur_run = run - prev_run
else:
cur_val = val
cur_ena = ena
cur_run = run
self.prev_data[prev_key] = counts # Store absolute value for next time
# Scale each raw event's delta by its own multiplexing ratio before
# summing across PMUs (e.g. cpu_core and cpu_atom on hybrid systems) so
# enabled time from an idle PMU does not inflate the multiplier of an
# active PMU.
scaled_val = cur_val * (cur_ena / float(cur_run)) if cur_run > 0 else float(cur_val)
self.data[key] = self.data.get(key, 0.0) + scaled_val
def get(self, event: str, cpu: int, thread: int) -> float:
"""Get scaled counter value."""
key = self.get_key(event, cpu, thread)
return self.data.get(key, 0.0)
@staticmethod
def _classify_event(name: str) -> Optional[str]:
"""Classify an event name as 'cycles' or 'instructions'."""
ev = name[6:-1] if name.startswith("evsel(") and name.endswith(")") else name
ev = ev.split(":", 1)[0]
if "/" in ev:
parts = [p for p in ev.split("/") if p]
if len(parts) >= 2:
ev = parts[1]
if ev in ("cycles", "cpu-cycles"):
return "cycles"
if ev == "instructions":
return "instructions"
return None
def process_stat_event(self, event: Any, name: Optional[str] = None) -> None:
"""Process PERF_RECORD_STAT and PERF_RECORD_STAT_ROUND events."""
if event.type == perf.RECORD_STAT:
if name:
event_name = self._classify_event(name)
if not event_name:
return
self.store(event_name, event.cpu, event.thread,
(event.val, event.ena, event.run), raw_name=name)
elif event.type == perf.RECORD_STAT_ROUND:
timestamp = getattr(event, "time", 0)
self.print_interval(timestamp)
self.data.clear()
self.recorded_pairs.clear()
def print_interval(self, timestamp: int) -> None:
"""Print CPI for the current interval."""
for cpu, thread in sorted(self.recorded_pairs):
cyc = self.get("cycles", cpu, thread)
ins = self.get("instructions", cpu, thread)
cpi = 0.0
if ins != 0:
cpi = cyc / float(ins)
t_sec = timestamp / 1000000000.0
print(f"{t_sec:15f}: cpu {cpu}, thread {thread} -> cpi {cpi:f} ({cyc:.0f}/{ins:.0f})",
flush=True)
def read_counters(self, evlist: Any) -> None:
"""Read counters live."""
for evsel in evlist:
name = str(evsel)
event_name = self._classify_event(name)
if not event_name:
continue
for cpu in evsel.cpus():
for thread in evsel.threads():
try:
counts = evsel.read(cpu, thread)
self.store(event_name, cpu, thread,
(counts.val, counts.ena, counts.run),
is_delta=True, raw_name=name)
except OSError:
pass
def run_file(self) -> None:
"""Process events from file."""
session: Optional[perf.session] = perf.session(
perf.data(self.args.input), stat=self.process_stat_event
)
try:
assert session is not None
session.process_events()
finally:
session = None
def _open_live_evlist(self) -> Any:
"""Open evlist for live mode, falling back to user-space or process scope on EACCES."""
threads = perf.thread_map(self.args.pid) if self.args.pid else None
candidates = [
("cycles,instructions", threads),
("cycles:u,instructions:u", threads),
]
if threads is None:
self_threads = perf.thread_map(os.getpid())
candidates.append(("cycles,instructions", self_threads))
candidates.append(("cycles:u,instructions:u", self_threads))
last_err: Optional[OSError] = None
for events, tmap in candidates:
evlist = None
try:
evlist = perf.parse_events(events, None, tmap)
for evsel in evlist:
evsel.read_format |= (
perf.FORMAT_TOTAL_TIME_ENABLED | perf.FORMAT_TOTAL_TIME_RUNNING
)
evlist.open()
evlist.enable()
return evlist
except PermissionError as e:
if evlist is not None:
evlist.close()
last_err = e
except OSError as e:
if evlist is not None:
evlist.close()
if e.errno == 13:
last_err = e
else:
raise
except BaseException:
if evlist is not None:
evlist.close()
raise
if last_err is not None:
raise last_err
raise RuntimeError("Failed to open events")
def run_live(self) -> None:
"""Read counters live."""
def handle_signal(_signum: int, _frame: Any) -> None:
raise KeyboardInterrupt
signal.signal(signal.SIGINT, signal.default_int_handler)
signal.signal(signal.SIGTERM, handle_signal)
evlist = None
try:
try:
evlist = self._open_live_evlist()
except OSError as e:
print(f"Failed to open events: {e}", file=sys.stderr)
sys.exit(1)
print("Live mode started. Press Ctrl+C to stop.", flush=True)
while True:
time.sleep(self.args.interval)
timestamp = time.time_ns()
self.read_counters(evlist)
self.print_interval(timestamp)
self.data.clear()
self.recorded_pairs.clear()
except KeyboardInterrupt:
print("\nStopped.", flush=True)
finally:
if evlist is not None:
evlist.close()
def main() -> None:
"""Main function."""
ap = argparse.ArgumentParser(description="Calculate CPI from perf stat data or live")
ap.add_argument("-i", "--input", help="Input file name (enables file mode)")
ap.add_argument("-I", "--interval", type=float, default=1.0,
help="Interval in seconds for live mode")
ap.add_argument("-p", "--pid", type=int,
help="Monitor specific process ID in live mode")
args = ap.parse_args()
analyzer = StatCpiAnalyzer(args)
if args.input:
analyzer.run_file()
else:
analyzer.run_live()
if __name__ == "__main__":
main()
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