1 #!/usr/bin/env python3
2 # SPDX-License-Identifier: GPL-2.0-only
3 #
4 # Copyright (C) 2024 Red Hat, Inc. Daniel Bristot de Oliveira <bristot@kernel.org>
5 #
6 # This is a sample code about how to use timerlat's timer by any workload
7 # so rtla can measure and provide auto-analysis for the overall latency (IOW
8 # the response time) for a task.
9 #
10 # Before running it, you need to dispatch timerlat with -U option in a terminal.
11 # Then # run this script pinned to a CPU on another terminal. For example:
12 #
13 # timerlat_load.py 1 -p 95
14 #
15 # The "Timerlat IRQ" is the IRQ latency, The thread latency is the latency
16 # for the python process to get the CPU. The Ret from user Timer Latency is
17 # the overall latency. In other words, it is the response time for that
18 # activation.
19 #
20 # This is just an example, the load is reading 20MB of data from /dev/full
21 # It is in python because it is easy to read :-)
22
23 import argparse
24 import sys
25 import os
26
27 parser = argparse.ArgumentParser(description='user-space timerlat thread in Python')
28 parser.add_argument("cpu", help='CPU to run timerlat thread')
29 parser.add_argument("-p", "--prio", help='FIFO priority')
30
31 args = parser.parse_args()
32
33 try:
34 affinity_mask = { int(args.cpu) }
35 except:
36 print("Invalid cpu: " + args.cpu)
37 exit(1)
38
39 try:
40 os.sched_setaffinity(0, affinity_mask);
41 except:
42 print("Error setting affinity")
43 exit(1)
44
45 if (args.prio):
46 try:
47 param = os.sched_param(int(args.prio))
48 os.sched_setscheduler(0, os.SCHED_FIFO, param)
49 except:
50 print("Error setting priority")
51 exit(1)
52
53 try:
54 timerlat_path = "/sys/kernel/tracing/osnoise/per_cpu/cpu" + args.cpu + "/timerlat_fd"
55 timerlat_fd = open(timerlat_path, 'r')
56 except:
57 print("Error opening timerlat fd, did you run timerlat -U?")
58 exit(1)
59
60 try:
61 data_fd = open("/dev/full", 'r');
62 except:
63 print("Error opening data fd")
64
65 while True:
66 try:
67 timerlat_fd.read(1)
68 data_fd.read(20*1024*1024)
69 except:
70 print("Leaving")
71 break
72
73 timerlat_fd.close()
74 data_fd.close()
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