| 1 | #!/usr/bin/env python3 |
| 2 | # |
| 3 | # KVM Flight Recorder - ring buffer tracing script |
| 4 | # |
| 5 | # Copyright (C) 2012 IBM Corp |
| 6 | # |
| 7 | # Author: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com> |
| 8 | # |
| 9 | # This script provides a command-line interface to kvm ftrace and is designed |
| 10 | # to be used as a flight recorder that is always running. To start in-memory |
| 11 | # recording: |
| 12 | # |
| 13 | # sudo kvm_flightrecorder start 8192 # 8 MB per-cpu ring buffers |
| 14 | # |
| 15 | # The per-cpu ring buffer size can be given in KB as an optional argument to |
| 16 | # the 'start' subcommand. |
| 17 | # |
| 18 | # To stop the flight recorder: |
| 19 | # |
| 20 | # sudo kvm_flightrecorder stop |
| 21 | # |
| 22 | # To dump the contents of the flight recorder (this can be done when the |
| 23 | # recorder is stopped or while it is running): |
| 24 | # |
| 25 | # sudo kvm_flightrecorder dump >/path/to/dump.txt |
| 26 | # |
| 27 | # To observe the trace while it is running, use the 'tail' subcommand: |
| 28 | # |
| 29 | # sudo kvm_flightrecorder tail |
| 30 | # |
| 31 | # Note that the flight recorder may impact overall system performance by |
| 32 | # consuming CPU cycles. No disk I/O is performed since the ring buffer holds a |
| 33 | # fixed-size in-memory trace. |
| 34 | |
| 35 | import sys |
| 36 | import os |
| 37 | |
| 38 | tracing_dir = '/sys/kernel/debug/tracing' |
| 39 | |
| 40 | def trace_path(*args): |
| 41 | return os.path.join(tracing_dir, *args) |
| 42 | |
| 43 | def write_file(path, data): |
| 44 | open(path, 'wb').write(data) |
| 45 | |
| 46 | def enable_event(subsystem, event, enable): |
| 47 | write_file(trace_path('events', subsystem, event, 'enable'), '1' if enable else '0') |
| 48 | |
| 49 | def enable_subsystem(subsystem, enable): |
| 50 | write_file(trace_path('events', subsystem, 'enable'), '1' if enable else '0') |
| 51 | |
| 52 | def start_tracing(): |
| 53 | enable_subsystem('kvm', True) |
| 54 | write_file(trace_path('tracing_on'), '1') |
| 55 | |
| 56 | def stop_tracing(): |
| 57 | write_file(trace_path('tracing_on'), '0') |
| 58 | enable_subsystem('kvm', False) |
| 59 | write_file(trace_path('events', 'enable'), '0') |
| 60 | write_file(trace_path('current_tracer'), 'nop') |
| 61 | |
| 62 | def dump_trace(): |
| 63 | tracefile = open(trace_path('trace'), 'r') |
| 64 | try: |
| 65 | lines = True |
| 66 | while lines: |
| 67 | lines = tracefile.readlines(64 * 1024) |
| 68 | sys.stdout.writelines(lines) |
| 69 | except KeyboardInterrupt: |
| 70 | pass |
| 71 | |
| 72 | def tail_trace(): |
| 73 | try: |
| 74 | for line in open(trace_path('trace_pipe'), 'r'): |
| 75 | sys.stdout.write(line) |
| 76 | except KeyboardInterrupt: |
| 77 | pass |
| 78 | |
| 79 | def usage(): |
| 80 | print('Usage: %s start [buffer_size_kb] | stop | dump | tail' % sys.argv[0]) |
| 81 | print('Control the KVM flight recorder tracing.') |
| 82 | sys.exit(0) |
| 83 | |
| 84 | def main(): |
| 85 | if len(sys.argv) < 2: |
| 86 | usage() |
| 87 | |
| 88 | cmd = sys.argv[1] |
| 89 | if cmd == '--version': |
| 90 | print('kvm_flightrecorder version 1.0') |
| 91 | sys.exit(0) |
| 92 | |
| 93 | if not os.path.isdir(tracing_dir): |
| 94 | print('Unable to tracing debugfs directory, try:') |
| 95 | print('mount -t debugfs none /sys/kernel/debug') |
| 96 | sys.exit(1) |
| 97 | if not os.access(tracing_dir, os.W_OK): |
| 98 | print('Unable to write to tracing debugfs directory, please run as root') |
| 99 | sys.exit(1) |
| 100 | |
| 101 | if cmd == 'start': |
| 102 | stop_tracing() # clean up first |
| 103 | |
| 104 | if len(sys.argv) == 3: |
| 105 | try: |
| 106 | buffer_size_kb = int(sys.argv[2]) |
| 107 | except ValueError: |
| 108 | print('Invalid per-cpu trace buffer size in KB') |
| 109 | sys.exit(1) |
| 110 | write_file(trace_path('buffer_size_kb'), str(buffer_size_kb)) |
| 111 | print('Per-CPU ring buffer size set to %d KB' % buffer_size_kb) |
| 112 | |
| 113 | start_tracing() |
| 114 | print('KVM flight recorder enabled') |
| 115 | elif cmd == 'stop': |
| 116 | stop_tracing() |
| 117 | print('KVM flight recorder disabled') |
| 118 | elif cmd == 'dump': |
| 119 | dump_trace() |
| 120 | elif cmd == 'tail': |
| 121 | tail_trace() |
| 122 | else: |
| 123 | usage() |
| 124 | |
| 125 | if __name__ == '__main__': |
| 126 | sys.exit(main()) |