diff --git a/scripts/kvm/kvm_flightrecorder b/scripts/kvm/kvm_flightrecorder new file mode 100755 index 0000000000..7fb1c2d1a7 --- /dev/null +++ b/scripts/kvm/kvm_flightrecorder @@ -0,0 +1,126 @@ +#!/usr/bin/env python +# +# KVM Flight Recorder - ring buffer tracing script +# +# Copyright (C) 2012 IBM Corp +# +# Author: Stefan Hajnoczi +# +# 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())