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simpletrace: refactor to separate responsibilities

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Moved event_mapping and event_id_to_name down one level in the function
call-stack to keep variable instantiation and usage closer (`process`
and `run` has no use of the variables; `read_trace_records` does).

Instead of passing event_mapping and event_id_to_name to the bottom of
the call-stack, we move their use to `read_trace_records`. This
separates responsibility and ownership of the information.

`read_record` now just reads the arguments from the file-object by
knowning the total number of bytes. Parsing it to specific arguments is
moved up to `read_trace_records`.

Special handling of dropped events removed, as they can be handled
by the general code.

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Mads Ynddal <m.ynddal@samsung.com>
Message-id: 20230926103436.25700-10-mads@ynddal.dk
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Mads Ynddal 2023-09-26 12:34:31 +02:00 committed by Stefan Hajnoczi
parent 87617b9ae6
commit 6f53641a98
1 changed files with 53 additions and 62 deletions
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115
scripts/simpletrace.py
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@ -31,6 +31,7 @@ record_type_event = 1
log_header_fmt = '=QQQ'
rec_header_fmt = '=QQII'
rec_header_fmt_len = struct.calcsize(rec_header_fmt)
class SimpleException(Exception):
pass
@ -43,35 +44,6 @@ def read_header(fobj, hfmt):
raise SimpleException('Error reading header. Wrong filetype provided?')
return struct.unpack(hfmt, hdr)
def get_record(event_mapping, event_id_to_name, rechdr, fobj):
"""Deserialize a trace record from a file into a tuple
(name, timestamp, pid, arg1, ..., arg6)."""
event_id, timestamp_ns, length, pid = rechdr
if event_id != dropped_event_id:
name = event_id_to_name[event_id]
try:
event = event_mapping[name]
except KeyError as e:
raise SimpleException(
f'{e} event is logged but is not declared in the trace events'
'file, try using trace-events-all instead.'
)
rec = (name, timestamp_ns, pid)
for type, name in event.args:
if is_string(type):
l = fobj.read(4)
(len,) = struct.unpack('=L', l)
s = fobj.read(len)
rec = rec + (s,)
else:
(value,) = struct.unpack('=Q', fobj.read(8))
rec = rec + (value,)
else:
(dropped_count,) = struct.unpack('=Q', fobj.read(8))
rec = ("dropped", timestamp_ns, pid, dropped_count)
return rec
def get_mapping(fobj):
(event_id, ) = struct.unpack('=Q', fobj.read(8))
(len, ) = struct.unpack('=L', fobj.read(4))
@ -79,10 +51,11 @@ def get_mapping(fobj):
return (event_id, name)
def read_record(event_mapping, event_id_to_name, fobj):
"""Deserialize a trace record from a file into a tuple (event_num, timestamp, pid, arg1, ..., arg6)."""
rechdr = read_header(fobj, rec_header_fmt)
return get_record(event_mapping, event_id_to_name, rechdr, fobj)
def read_record(fobj):
"""Deserialize a trace record from a file into a tuple (event_num, timestamp, pid, args)."""
event_id, timestamp_ns, record_length, record_pid = read_header(fobj, rec_header_fmt)
args_payload = fobj.read(record_length - rec_header_fmt_len)
return (event_id, timestamp_ns, record_pid, args_payload)
def read_trace_header(fobj):
"""Read and verify trace file header"""
@ -97,17 +70,28 @@ def read_trace_header(fobj):
if log_version != 4:
raise ValueError(f'Log format {log_version} not supported with this QEMU release!')
def read_trace_records(event_mapping, event_id_to_name, fobj):
"""Deserialize trace records from a file, yielding record tuples (event_num, timestamp, pid, arg1, ..., arg6).
Note that `event_id_to_name` is modified if the file contains mapping records.
def read_trace_records(events, fobj, read_header):
"""Deserialize trace records from a file, yielding record tuples (event, event_num, timestamp, pid, arg1, ..., arg6).
Args:
event_mapping (str -> Event): events dict, indexed by name
event_id_to_name (int -> str): event names dict, indexed by event ID
fobj (file): input file
read_header (bool): whether headers were read from fobj
"""
frameinfo = inspect.getframeinfo(inspect.currentframe())
dropped_event = Event.build("Dropped_Event(uint64_t num_events_dropped)",
frameinfo.lineno + 1, frameinfo.filename)
event_mapping = {e.name: e for e in events}
event_mapping["dropped"] = dropped_event
event_id_to_name = {dropped_event_id: "dropped"}
# If there is no header assume event ID mapping matches events list
if not read_header:
for event_id, event in enumerate(events):
event_id_to_name[event_id] = event.name
while True:
t = fobj.read(8)
if len(t) == 0:
@ -115,12 +99,35 @@ def read_trace_records(event_mapping, event_id_to_name, fobj):
(rectype, ) = struct.unpack('=Q', t)
if rectype == record_type_mapping:
event_id, name = get_mapping(fobj)
event_id_to_name[event_id] = name
event_id, event_name = get_mapping(fobj)
event_id_to_name[event_id] = event_name
else:
rec = read_record(event_mapping, event_id_to_name, fobj)
event_id, timestamp_ns, pid, args_payload = read_record(fobj)
event_name = event_id_to_name[event_id]
yield rec
try:
event = event_mapping[event_name]
except KeyError as e:
raise SimpleException(
f'{e} event is logged but is not declared in the trace events'
'file, try using trace-events-all instead.'
)
offset = 0
args = []
for type, _ in event.args:
if is_string(type):
(length,) = struct.unpack_from('=L', args_payload, offset=offset)
offset += 4
s = args_payload[offset:offset+length]
offset += length
args.append(s)
else:
(value,) = struct.unpack_from('=Q', args_payload, offset=offset)
offset += 8
args.append(value)
yield (event_mapping[event_name], event_name, timestamp_ns, pid) + tuple(args)
class Analyzer:
"""A trace file analyzer which processes trace records.
@ -202,20 +209,6 @@ def process(events, log, analyzer, read_header=True):
if read_header:
read_trace_header(log)
frameinfo = inspect.getframeinfo(inspect.currentframe())
dropped_event = Event.build("Dropped_Event(uint64_t num_events_dropped)",
frameinfo.lineno + 1, frameinfo.filename)
event_mapping = {"dropped": dropped_event}
event_id_to_name = {dropped_event_id: "dropped"}
for event in events_list:
event_mapping[event.name] = event
# If there is no header assume event ID mapping matches events list
if not read_header:
for event_id, event in enumerate(events_list):
event_id_to_name[event_id] = event.name
def build_fn(analyzer, event):
if isinstance(event, str):
return analyzer.catchall
@ -238,12 +231,10 @@ def process(events, log, analyzer, read_header=True):
with analyzer:
fn_cache = {}
for rec in read_trace_records(event_mapping, event_id_to_name, log):
event_num = rec[0]
event = event_mapping[event_num]
if event_num not in fn_cache:
fn_cache[event_num] = build_fn(analyzer, event)
fn_cache[event_num](event, rec)
for event, event_id, timestamp_ns, record_pid, *rec_args in read_trace_records(events, log, read_header):
if event_id not in fn_cache:
fn_cache[event_id] = build_fn(analyzer, event)
fn_cache[event_id](event, (event_id, timestamp_ns, record_pid, *rec_args))
if close_log:
log.close()