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