def _open_for_cpu(self, pmu: int, cpu: int, event: Event):
"""Opens file descriptor for event selected via event_name, for selected cpu"""
group_file = self._group_event_leader_files_per_pmu.get(pmu,
{}).get(cpu)
is_group_leader = group_file is None
# man perf_event_open cite regarding the disabled variable:
# When creating an event group, typically the group leader is
# initialized with disabled set to 1 and any child events are
# initialized with disabled set to 0. Despite disabled being 0,
# the child events will not start until the group leader is
# enabled.
# Disabled when creating new leader.
# Enabled for children
flags = 0 # pc.PERF_FLAG_FD_CLOEXEC
pid = -1
if is_group_leader:
disabled = True
group_fd = -1
else:
disabled = False
group_fd = group_file.fileno()
self.attr = _create_event_attributes(
pmu,
disabled,
event,
)
pfd = _perf_event_open(perf_event_attr=ctypes.byref(self.attr),
pid=pid,
cpu=cpu,
group_fd=group_fd,
flags=flags)
perf_event_file = _create_file_from_fd(pfd)
if is_group_leader:
self._group_event_leader_files_per_pmu[pmu][cpu] = perf_event_file
else:
self._event_files.append(perf_event_file)
def test_create_file_from_invalid_fd():
with pytest.raises(perf.UnableToOpenPerfEvents):
perf._create_file_from_fd(-1)
def test_create_file_from_valid_fd(_):
file = perf._create_file_from_fd(1)
assert file is not None