hw/spitz: Don't prematurely explode QEMUMachineInitArgs
[qemu/pbrook.git] / scripts / kvm / kvm_flightrecorder
blob7fb1c2d1a7caac6f8801d27c6b64b8443df766c2
1 #!/usr/bin/env python
3 # KVM Flight Recorder - ring buffer tracing script
5 # Copyright (C) 2012 IBM Corp
7 # Author: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
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:
13 # sudo kvm_flightrecorder start 8192 # 8 MB per-cpu ring buffers
15 # The per-cpu ring buffer size can be given in KB as an optional argument to
16 # the 'start' subcommand.
18 # To stop the flight recorder:
20 # sudo kvm_flightrecorder stop
22 # To dump the contents of the flight recorder (this can be done when the
23 # recorder is stopped or while it is running):
25 # sudo kvm_flightrecorder dump >/path/to/dump.txt
27 # To observe the trace while it is running, use the 'tail' subcommand:
29 # sudo kvm_flightrecorder tail
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.
35 import sys
36 import os
38 tracing_dir = '/sys/kernel/debug/tracing'
40 def trace_path(*args):
41 return os.path.join(tracing_dir, *args)
43 def write_file(path, data):
44 open(path, 'wb').write(data)
46 def enable_event(subsystem, event, enable):
47 write_file(trace_path('events', subsystem, event, 'enable'), '1' if enable else '0')
49 def enable_subsystem(subsystem, enable):
50 write_file(trace_path('events', subsystem, 'enable'), '1' if enable else '0')
52 def start_tracing():
53 enable_subsystem('kvm', True)
54 write_file(trace_path('tracing_on'), '1')
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')
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
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
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)
84 def main():
85 if len(sys.argv) < 2:
86 usage()
88 cmd = sys.argv[1]
89 if cmd == '--version':
90 print 'kvm_flightrecorder version 1.0'
91 sys.exit(0)
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)
101 if cmd == 'start':
102 stop_tracing() # clean up first
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
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()
125 if __name__ == '__main__':
126 sys.exit(main())