#!/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()