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"""Functions for reading and interpreting binary sched_trace files.
"""
import struct
HEADER_LEN = 8 # bytes
PAYLOAD_LEN = 16 # bytes
RECORD_LEN = 24 # bytes
EVENT_NAMES = [
"ST_NAME",
"ST_PARAM",
"ST_RELEASE",
"ST_ASSIGNED",
"ST_SWITCH_TO",
"ST_SWITCH_AWAY",
"ST_COMPLETION",
"ST_BLOCK",
"ST_RESUME",
"ST_ACTION",
"ST_SYS_RELEASE"
]
EVENTS = {}
for i, ev in enumerate(EVENT_NAMES):
EVENTS[ev] = i + 1
EVENTS[i + 1] = ev
def event(id):
return EVENTS[id] if id in EVENTS else id
# struct st_trace_header {
# u8 type; /* Of what type is this record? */
# u8 cpu; /* On which CPU was it recorded? */
# u16 pid; /* PID of the task. */
# u32 job; /* The job sequence number. */
# };
def get_event(mmaped_trace, index):
offset = index * RECORD_LEN
# first byte in the record is the event type ID
return ord(mmaped_trace[offset])
# return struct.unpack("B", raw_data[:1])[0]
def unpack_header(raw_data):
"""Returns (type, cpu, pid, job id)"""
return struct.unpack("BBHI", raw_data[:HEADER_LEN])
def unpack_release(raw_data):
"""Returns (release, deadline)"""
return struct.unpack("QQ", raw_data[HEADER_LEN:RECORD_LEN])
def unpack_switch_to(raw_data):
"""Returns (when, exec_time_so_far)"""
return struct.unpack("QI", raw_data[HEADER_LEN:RECORD_LEN - 4])
def unpack_switch_away(raw_data):
"""Returns (when, exec_time_so_far)"""
return struct.unpack("QQ", raw_data[HEADER_LEN:RECORD_LEN])
def unpack_completion(raw_data):
"""Returns (when, exec_time, forced)"""
(when, exec_time) = struct.unpack("QQ", raw_data[HEADER_LEN:RECORD_LEN])
return (when, exec_time >> 1, exec_time & 0x1)
def unpack_block(raw_data):
"""Returns (when,)"""
return struct.unpack("Q", raw_data[HEADER_LEN:RECORD_LEN - 8])
def unpack_resume(raw_data):
"""Returns (when,)"""
return struct.unpack("Q", raw_data[HEADER_LEN:RECORD_LEN - 8])
def unpack_sys_release(raw_data):
"""Returns (when, release)"""
return struct.unpack("QQ", raw_data[HEADER_LEN:RECORD_LEN])
def unpack_name(raw_data):
"""Returns (name,)"""
data = raw_data[HEADER_LEN:RECORD_LEN]
null_byte_idx = data.find('\0')
if null_byte_idx > -1:
data = data[:null_byte_idx]
return (data,)
def unpack_param(raw_data):
"""Returns (WCET, period, phase, partition)"""
return struct.unpack("IIIB", raw_data[HEADER_LEN:RECORD_LEN - 3])
UNPACK = {
EVENTS['ST_RELEASE']: unpack_release,
EVENTS['ST_SWITCH_TO']: unpack_switch_to,
EVENTS['ST_SWITCH_AWAY']: unpack_switch_away,
EVENTS['ST_COMPLETION']: unpack_completion,
EVENTS['ST_BLOCK']: unpack_block,
EVENTS['ST_RESUME']: unpack_resume,
EVENTS['ST_SYS_RELEASE']: unpack_sys_release,
EVENTS['ST_NAME']: unpack_name,
EVENTS['ST_PARAM']: unpack_param,
}
EVENTS_WITHOUT_TIMESTAMP = frozenset([
EVENTS['ST_NAME'],
EVENTS['ST_PARAM'],
])
def when(raw_data):
ev = get_event(raw_data)
if ev in EVENTS_WITHOUT_TIMESTAMP:
return 0
else:
# always first element for all others
return UNPACK[ev](raw_data)[0]
def unpack(raw_data):
hdr = unpack_header(raw_data)
payload = UNPACK[hdr[0]](raw_data)
return hdr + payload
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