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Annotation of qemu/scripts/kvm/kvm_flightrecorder, revision 1.1.1.1

1.1       root        1: #!/usr/bin/env python
                      2: #
                      3: # KVM Flight Recorder - ring buffer tracing script
                      4: #
                      5: # Copyright (C) 2012 IBM Corp
                      6: #
                      7: # Author: Stefan Hajnoczi <[email protected]>
                      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())

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