← Back to branch summary

~bzr-pqm/bzr/bzr.dev

« back to all changes in this revision

Viewing changes to bzrlib/lsprof.py

  • Committer: Robert Collins
  • Date: 2010-07-04 06:22:11 UTC
  • mto: This revision was merged to the branch mainline in revision 5332.
  • Revision ID: robertc@robertcollins.net-20100704062211-tk9hw6bnsn5x47fm
``bzrlib.lsprof.profile`` will no longer silently generate bad threaded
profiles when concurrent profile requests are made. Instead the profile
requests will be serialised. Reentrant requests will now deadlock.
(Robert Collins)

Show diffs side-by-side

added added

removed removed

Lines of Context:
bzrlib/lsprof.py
10
10
import threading
11
11
from _lsprof import Profiler, profiler_entry
12
12
 
 
13
from bzrlib import errors
13
14
 
14
15
__all__ = ['profile', 'Stats']
15
16
 
20
21
    raised, pass in a closure that will catch the exceptions and transform them
21
22
    appropriately for your driver function.
22
23
 
 
24
    Important caveat: only one profile can execute at a time. See BzrProfiler
 
25
    for details.
 
26
 
23
27
    :return: The functions return value and a stats object.
24
28
    """
25
29
    profiler = BzrProfiler()
41
45
    To use it, create a BzrProfiler and call start() on it. Some arbitrary
42
46
    time later call stop() to stop profiling and retrieve the statistics
43
47
    from the code executed in the interim.
 
48
 
 
49
    Note that profiling involves a threading.Lock around the actual profiling.
 
50
    This is needed because profiling involves global manipulation of the python
 
51
    interpreter state. As such you cannot perform multiple profiles at once.
 
52
    Trying to do so will lock out the second profiler unless the global 
 
53
    bzrlib.lsprof.BzrProfiler.profiler_block is set to 0. Setting it to 0 will
 
54
    cause profiling to fail rather than blocking.
44
55
    """
45
56
 
 
57
    profiler_block = 1
 
58
    """Serialise rather than failing to profile concurrent profile requests."""
 
59
 
 
60
    profiler_lock = threading.Lock()
 
61
    """Global lock used to serialise profiles."""
 
62
 
46
63
    def start(self):
47
64
        """Start profiling.
48
65
        
51
68
        """
52
69
        self._g_threadmap = {}
53
70
        self.p = Profiler()
54
 
        self.p.enable(subcalls=True)
55
 
        threading.setprofile(self._thread_profile)
 
71
        permitted = self.__class__.profiler_lock.acquire(
 
72
            self.__class__.profiler_block)
 
73
        if not permitted:
 
74
            raise errors.InternalBzrError(msg="Already profiling something")
 
75
        try:
 
76
            self.p.enable(subcalls=True)
 
77
            threading.setprofile(self._thread_profile)
 
78
        except:
 
79
            self.__class__.profiler_lock.release()
 
80
            raise
56
81
 
57
82
    def stop(self):
58
83
        """Stop profiling.
62
87
 
63
88
        :return: A bzrlib.lsprof.Stats object.
64
89
        """
65
 
        self.p.disable()
66
 
        for pp in self._g_threadmap.values():
67
 
            pp.disable()
68
 
        threading.setprofile(None)
69
 
        p = self.p
70
 
        self.p = None
71
 
        threads = {}
72
 
        for tid, pp in self._g_threadmap.items():
73
 
            threads[tid] = Stats(pp.getstats(), {})
74
 
        self._g_threadmap = None
75
 
        return Stats(p.getstats(), threads)
 
90
        try:
 
91
            self.p.disable()
 
92
            for pp in self._g_threadmap.values():
 
93
                pp.disable()
 
94
            threading.setprofile(None)
 
95
            p = self.p
 
96
            self.p = None
 
97
            threads = {}
 
98
            for tid, pp in self._g_threadmap.items():
 
99
                threads[tid] = Stats(pp.getstats(), {})
 
100
            self._g_threadmap = None
 
101
            return Stats(p.getstats(), threads)
 
102
        finally:
 
103
            self.__class__.profiler_lock.release()
76
104
 
77
105
    def _thread_profile(self, f, *args, **kwds):
78
106
        # we lose the first profile point for a new thread in order to