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Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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12345678910111213141516171819202122232425262728293031323334353637383940414243444546474849505152535455565758596061626364656667686970717273747576777879#!/usr/bin/env python3# SPDX-License-Identifier: GPL-2.0-only## Copyright (C) 2024 Red Hat, Inc. Daniel Bristot de Oliveira <bristot@kernel.org>## This is a sample code about how to use timerlat's timer by any workload# so rtla can measure and provide auto-analysis for the overall latency (IOW# the response time) for a task.## Before running it, you need to dispatch timerlat with -U option in a terminal.# Then # run this script pinned to a CPU on another terminal. For example:## timerlat_load.py 1 -p 95## The "Timerlat IRQ" is the IRQ latency, The thread latency is the latency# for the python process to get the CPU. The Ret from user Timer Latency is# the overall latency. In other words, it is the response time for that# activation.## This is just an example, the load is reading 20MB of data from /dev/full# It is in python because it is easy to read :-)
import argparseimport sysimport os
parser = argparse.ArgumentParser(description='user-space timerlat thread in Python')parser.add_argument("cpu", type=int, help='CPU to run timerlat thread')parser.add_argument("-p", "--prio", type=int, help='FIFO priority')args = parser.parse_args()
try: affinity_mask = {args.cpu} os.sched_setaffinity(0, affinity_mask)except Exception as e: print(f"Error setting affinity: {e}") sys.exit(1)
if args.prio: try: param = os.sched_param(args.prio) os.sched_setscheduler(0, os.SCHED_FIFO, param) except Exception as e: print(f"Error setting priority: {e}") sys.exit(1)
try: timerlat_path = f"/sys/kernel/tracing/osnoise/per_cpu/cpu{args.cpu}/timerlat_fd" timerlat_fd = open(timerlat_path, 'r')except PermissionError: print("Permission denied. Please check your access rights.") sys.exit(1)except OSError: print("Error opening timerlat fd, did you run timerlat -U?") sys.exit(1)
try: data_fd = open("/dev/full", 'r')except Exception as e: print(f"Error opening data fd: {e}") sys.exit(1)
while True: try: timerlat_fd.read(1) data_fd.read(20 * 1024 * 1024) except KeyboardInterrupt: print("Leaving") break except IOError as e: print(f"I/O error occurred: {e}") break except Exception as e: print(f"Unexpected error: {e}") break
timerlat_fd.close()data_fd.close()