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127 lines
3.6 KiB
Python
127 lines
3.6 KiB
Python
#!/usr/bin/env python3
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#
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# KVM Flight Recorder - ring buffer tracing script
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#
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# Copyright (C) 2012 IBM Corp
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#
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# Author: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
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#
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# This script provides a command-line interface to kvm ftrace and is designed
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# to be used as a flight recorder that is always running. To start in-memory
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# recording:
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#
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# sudo kvm_flightrecorder start 8192 # 8 MB per-cpu ring buffers
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#
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# The per-cpu ring buffer size can be given in KB as an optional argument to
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# the 'start' subcommand.
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#
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# To stop the flight recorder:
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#
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# sudo kvm_flightrecorder stop
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#
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# To dump the contents of the flight recorder (this can be done when the
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# recorder is stopped or while it is running):
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#
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# sudo kvm_flightrecorder dump >/path/to/dump.txt
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#
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# To observe the trace while it is running, use the 'tail' subcommand:
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#
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# sudo kvm_flightrecorder tail
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#
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# Note that the flight recorder may impact overall system performance by
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# consuming CPU cycles. No disk I/O is performed since the ring buffer holds a
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# fixed-size in-memory trace.
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import sys
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import os
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tracing_dir = '/sys/kernel/debug/tracing'
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def trace_path(*args):
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return os.path.join(tracing_dir, *args)
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def write_file(path, data):
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open(path, 'wb').write(data)
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def enable_event(subsystem, event, enable):
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write_file(trace_path('events', subsystem, event, 'enable'), '1' if enable else '0')
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def enable_subsystem(subsystem, enable):
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write_file(trace_path('events', subsystem, 'enable'), '1' if enable else '0')
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def start_tracing():
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enable_subsystem('kvm', True)
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write_file(trace_path('tracing_on'), '1')
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def stop_tracing():
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write_file(trace_path('tracing_on'), '0')
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enable_subsystem('kvm', False)
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write_file(trace_path('events', 'enable'), '0')
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write_file(trace_path('current_tracer'), 'nop')
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def dump_trace():
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tracefile = open(trace_path('trace'), 'r')
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try:
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lines = True
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while lines:
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lines = tracefile.readlines(64 * 1024)
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sys.stdout.writelines(lines)
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except KeyboardInterrupt:
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pass
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def tail_trace():
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try:
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for line in open(trace_path('trace_pipe'), 'r'):
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sys.stdout.write(line)
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except KeyboardInterrupt:
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pass
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def usage():
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print('Usage: %s start [buffer_size_kb] | stop | dump | tail' % sys.argv[0])
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print('Control the KVM flight recorder tracing.')
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sys.exit(0)
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def main():
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if len(sys.argv) < 2:
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usage()
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cmd = sys.argv[1]
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if cmd == '--version':
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print('kvm_flightrecorder version 1.0')
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sys.exit(0)
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if not os.path.isdir(tracing_dir):
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print('Unable to tracing debugfs directory, try:')
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print('mount -t debugfs none /sys/kernel/debug')
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sys.exit(1)
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if not os.access(tracing_dir, os.W_OK):
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print('Unable to write to tracing debugfs directory, please run as root')
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sys.exit(1)
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if cmd == 'start':
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stop_tracing() # clean up first
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if len(sys.argv) == 3:
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try:
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buffer_size_kb = int(sys.argv[2])
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except ValueError:
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print('Invalid per-cpu trace buffer size in KB')
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sys.exit(1)
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write_file(trace_path('buffer_size_kb'), str(buffer_size_kb))
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print('Per-CPU ring buffer size set to %d KB' % buffer_size_kb)
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start_tracing()
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print('KVM flight recorder enabled')
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elif cmd == 'stop':
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stop_tracing()
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print('KVM flight recorder disabled')
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elif cmd == 'dump':
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dump_trace()
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elif cmd == 'tail':
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tail_trace()
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else:
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usage()
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if __name__ == '__main__':
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sys.exit(main())
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