def start(self, test):
"""
Start ftrace profiler
:param test: Autotest test in which the profiler will operate on.
"""
# Make sure debugfs is mounted and tracing disabled.
utils.system('%s reset' % self.trace_cmd)
output_dir = os.path.join(test.profdir, 'ftrace')
if not os.path.isdir(output_dir):
os.makedirs(output_dir)
self.output = os.path.join(output_dir, 'trace.dat')
cmd = [self.trace_cmd, 'record', '-o', self.output]
cmd += self.trace_cmd_args
self.record_job = utils.BgJob(self.join_command(cmd),
stderr_tee=utils.TEE_TO_LOGS)
# Wait for tracing to be enabled. If trace-cmd dies before enabling
# tracing, then there was a problem.
tracing_on = os.path.join(self.tracing_dir, 'tracing_on')
while (self.record_job.sp.poll() is None and
utils.read_file(tracing_on).strip() != '1'):
time.sleep(0.1)
if self.record_job.sp.poll() is not None:
utils.join_bg_jobs([self.record_job])
raise error.CmdError(self.record_job.command,
self.record_job.sp.returncode,
'trace-cmd exited early.')
def stop(self, test):
"""
Stop ftrace profiler.
:param test: Autotest test in which the profiler will operate on.
"""
os.kill(self.record_job.sp.pid, signal.SIGINT)
utils.join_bg_jobs([self.record_job])
# shrink the buffer to free memory.
utils.system('%s reset -b 1' % self.trace_cmd)
# compress output
utils.system('bzip2 %s' % self.output)
compressed_output = self.output + '.bz2'
# if the compressed trace file is large (10MB), just delete it.
compressed_output_size = os.path.getsize(compressed_output)
if compressed_output_size > 10 * 1024 * 1024:
logging.warn('Deleting large trace file %s (%d bytes)',
compressed_output, compressed_output_size)
os.remove(compressed_output)
# remove per-cpu files in case trace-cmd died.
utils.system('rm -f %s.cpu*' % self.output)
