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simpletrace: Make simpletrace.py a Python module

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The simpletrace.py script pretty-prints a binary trace file.  Most of
the code can be reused by trace file analysis scripts, so turn it into a
module.

Here is an example script that uses the new simpletrace module:

  #!/usr/bin/env python
  # Print virtqueue elements that were never returned to the guest.

  import simpletrace

  class VirtqueueRequestTracker(simpletrace.Analyzer):
      def __init__(self):
          self.elems = set()

      def virtqueue_pop(self, vq, elem, in_num, out_num):
          self.elems.add(elem)

      def virtqueue_fill(self, vq, elem, length, idx):
          self.elems.remove(elem)

      def end(self):
          for elem in self.elems:
              print hex(elem)

  simpletrace.run(VirtqueueRequestTracker())

The simpletrace API is based around the Analyzer class.  Users implement
an analyzer subclass and add methods for trace events they want to
process.  A catchall() method is invoked for trace events which do not
have dedicated methods.  Finally, there are also begin() and end()
methods like in sed that can be used to perform setup or print
statistics at the end.

A binary trace file is processed either with:

  simpletrace.run(analyzer) # uses command-line args

or with:

  simpletrace.process('path/to/trace-events',
                      'path/to/trace-file',
                      analyzer)

Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
This commit is contained in:
Stefan Hajnoczi 2011-02-22 13:59:41 +00:00 committed by Aurelien Jarno
parent 0c1592d935
commit 59da668492
1 changed files with 86 additions and 29 deletions
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115
scripts/simpletrace.py
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@ -9,9 +9,9 @@
#
# For help see docs/tracing.txt
import sys
import struct
import re
import inspect
header_event_id = 0xffffffffffffffff
header_magic = 0xf2b177cb0aa429b4
@ -21,12 +21,8 @@ trace_fmt = '=QQQQQQQQ'
trace_len = struct.calcsize(trace_fmt)
event_re = re.compile(r'(disable\s+)?([a-zA-Z0-9_]+)\(([^)]*)\).*')
def err(msg):
sys.stderr.write(msg + '\n')
sys.exit(1)
def parse_events(fobj):
"""Parse a trace-events file."""
"""Parse a trace-events file into {event_num: (name, arg1, ...)}."""
def get_argnames(args):
"""Extract argument names from a parameter list."""
@ -45,20 +41,20 @@ def parse_events(fobj):
return events
def read_record(fobj):
"""Deserialize a trace record from a file."""
"""Deserialize a trace record from a file into a tuple (event_num, timestamp, arg1, ..., arg6)."""
s = fobj.read(trace_len)
if len(s) != trace_len:
return None
return struct.unpack(trace_fmt, s)
def read_trace_file(fobj):
"""Deserialize trace records from a file."""
"""Deserialize trace records from a file, yielding record tuples (event_num, timestamp, arg1, ..., arg6)."""
header = read_record(fobj)
if header is None or \
header[0] != header_event_id or \
header[1] != header_magic or \
header[2] != header_version:
err('not a trace file or incompatible version')
raise ValueError('not a trace file or incompatible version')
while True:
rec = read_record(fobj)
@ -67,27 +63,88 @@ def read_trace_file(fobj):
yield rec
class Formatter(object):
def __init__(self, events):
self.events = events
self.last_timestamp = None
class Analyzer(object):
"""A trace file analyzer which processes trace records.
def format_record(self, rec):
if self.last_timestamp is None:
self.last_timestamp = rec[1]
delta_ns = rec[1] - self.last_timestamp
self.last_timestamp = rec[1]
An analyzer can be passed to run() or process(). The begin() method is
invoked, then each trace record is processed, and finally the end() method
is invoked.
event = self.events[rec[0]]
fields = [event[0], '%0.3f' % (delta_ns / 1000.0)]
for i in xrange(1, len(event)):
fields.append('%s=0x%x' % (event[i], rec[i + 1]))
return ' '.join(fields)
If a method matching a trace event name exists, it is invoked to process
that trace record. Otherwise the catchall() method is invoked."""
if len(sys.argv) != 3:
err('usage: %s <trace-events> <trace-file>' % sys.argv[0])
def begin(self):
"""Called at the start of the trace."""
pass
events = parse_events(open(sys.argv[1], 'r'))
formatter = Formatter(events)
for rec in read_trace_file(open(sys.argv[2], 'rb')):
print formatter.format_record(rec)
def catchall(self, event, rec):
"""Called if no specific method for processing a trace event has been found."""
pass
def end(self):
"""Called at the end of the trace."""
pass
def process(events, log, analyzer):
"""Invoke an analyzer on each event in a log."""
if isinstance(events, str):
events = parse_events(open(events, 'r'))
if isinstance(log, str):
log = open(log, 'rb')
def build_fn(analyzer, event):
fn = getattr(analyzer, event[0], None)
if fn is None:
return analyzer.catchall
event_argcount = len(event) - 1
fn_argcount = len(inspect.getargspec(fn)[0]) - 1
if fn_argcount == event_argcount + 1:
# Include timestamp as first argument
return lambda _, rec: fn(*rec[1:2 + fn_argcount])
else:
# Just arguments, no timestamp
return lambda _, rec: fn(*rec[2:2 + fn_argcount])
analyzer.begin()
fn_cache = {}
for rec in read_trace_file(log):
event_num = rec[0]
event = events[event_num]
if event_num not in fn_cache:
fn_cache[event_num] = build_fn(analyzer, event)
fn_cache[event_num](event, rec)
analyzer.end()
def run(analyzer):
"""Execute an analyzer on a trace file given on the command-line.
This function is useful as a driver for simple analysis scripts. More
advanced scripts will want to call process() instead."""
import sys
if len(sys.argv) != 3:
sys.stderr.write('usage: %s <trace-events> <trace-file>\n' % sys.argv[0])
sys.exit(1)
events = parse_events(open(sys.argv[1], 'r'))
process(events, sys.argv[2], analyzer)
if __name__ == '__main__':
class Formatter(Analyzer):
def __init__(self):
self.last_timestamp = None
def catchall(self, event, rec):
timestamp = rec[1]
if self.last_timestamp is None:
self.last_timestamp = timestamp
delta_ns = timestamp - self.last_timestamp
self.last_timestamp = timestamp
fields = [event[0], '%0.3f' % (delta_ns / 1000.0)]
for i in xrange(1, len(event)):
fields.append('%s=0x%x' % (event[i], rec[i + 1]))
print ' '.join(fields)
run(Formatter())