mirror of https://github.com/python/cpython
Issue #10576: Add a progress callback to gcmodule
This commit is contained in:
Kristján Valur Jónsson
parent
c014df7edf
commit
69c635266e
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@ -153,8 +153,8 @@ The :mod:`gc` module provides the following functions:
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.. versionadded:: 3.1
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The following variable is provided for read-only access (you can mutate its
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value but should not rebind it):
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The following variables are provided for read-only access (you can mutate the
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values but should not rebind them):
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.. data:: garbage
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@ -183,6 +183,41 @@ value but should not rebind it):
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:const:`DEBUG_UNCOLLECTABLE` is set, in addition all uncollectable objects
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are printed.
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.. data:: callbacks
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A list of callbacks that will be invoked by the garbage collector before and
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after collection. The callbacks will be called with two arguments,
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:arg:`phase` and :arg:`info`.
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:arg:`phase` can one of two values:
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"start": The garbage collection is about to start.
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"stop": The garbage collection has finished.
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:arg:`info` provides more information for the callback. The following
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keys are currently defined:
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"generation": The oldest generation being collected.
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"collected": When :arg:`phase` is "stop", the number of objects
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successfully collected.
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"uncollectable": when :arg:`phase` is "stop", the number of objects
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that could not be collected and were put in :data:`garbage`.
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Applications can add their own callbacks to this list. The primary
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use cases are:
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Gathering statistics about garbage collection, such as how often
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various generations are collected, and how long the collection
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takes.
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Allowing applications to identify and clear their own uncollectable
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types when they appear in :data:`garbage`.
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.. versionadded:: 3.3
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The following constants are provided for use with :func:`set_debug`:
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@ -32,6 +32,20 @@ class GC_Detector(object):
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# gc collects it.
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self.wr = weakref.ref(C1055820(666), it_happened)
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class Uncollectable(object):
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"""Create a reference cycle with multiple __del__ methods.
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An object in a reference cycle will never have zero references,
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and so must be garbage collected. If one or more objects in the
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cycle have __del__ methods, the gc refuses to guess an order,
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and leaves the cycle uncollected."""
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def __init__(self, partner=None):
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if partner is None:
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self.partner = Uncollectable(partner=self)
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else:
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self.partner = partner
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def __del__(self):
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pass
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### Tests
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###############################################################################
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@ -528,6 +542,126 @@ class GCTests(unittest.TestCase):
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self.assertNotIn(b"uncollectable objects at shutdown", stderr)
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class GCCallbackTests(unittest.TestCase):
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def setUp(self):
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# Save gc state and disable it.
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self.enabled = gc.isenabled()
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gc.disable()
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self.debug = gc.get_debug()
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gc.set_debug(0)
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gc.callbacks.append(self.cb1)
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gc.callbacks.append(self.cb2)
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def tearDown(self):
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# Restore gc state
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del self.visit
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gc.callbacks.remove(self.cb1)
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gc.callbacks.remove(self.cb2)
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gc.set_debug(self.debug)
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if self.enabled:
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gc.enable()
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# destroy any uncollectables
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gc.collect()
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for obj in gc.garbage:
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if isinstance(obj, Uncollectable):
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obj.partner = None
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del gc.garbage[:]
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gc.collect()
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othergarbage = []
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def preclean(self):
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# Remove all fluff from the system. Invoke this function
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# manually rather than through self.setUp() for maximum
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# safety.
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self.visit = []
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gc.collect()
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garbage, gc.garbage[:] = gc.garbage[:], []
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self.othergarbage.append(garbage)
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self.visit = []
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def cb1(self, phase, info):
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self.visit.append((1, phase, dict(info)))
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def cb2(self, phase, info):
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self.visit.append((2, phase, dict(info)))
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if phase == "stop" and hasattr(self, "cleanup"):
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# Clean Uncollectable from garbage
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uc = [e for e in gc.garbage if isinstance(e, Uncollectable)]
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gc.garbage[:] = [e for e in gc.garbage
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if not isinstance(e, Uncollectable)]
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for e in uc:
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e.partner = None
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def testCollect(self):
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self.preclean()
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gc.collect()
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# Algorithmically verify the contents of self.visit
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# because it is long and tortuous.
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# Count the number of visits to each callback
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n = [v[0] for v in self.visit]
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n1 = [i for i in n if i == 1]
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n2 = [i for i in n if i == 2]
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self.assertEqual(n1, [1]*2)
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self.assertEqual(n2, [2]*2)
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# Count that we got the right number of start and stop callbacks.
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n = [v[1] for v in self.visit]
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n1 = [i for i in n if i == "start"]
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n2 = [i for i in n if i == "stop"]
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self.assertEqual(n1, ["start"]*2)
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self.assertEqual(n2, ["stop"]*2)
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# Check that we got the right info dict for all callbacks
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for v in self.visit:
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info = v[2]
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self.assertTrue("generation" in info)
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self.assertTrue("collected" in info)
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self.assertTrue("uncollectable" in info)
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def testCollectGen(self):
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self.preclean()
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gc.collect(2)
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for v in self.visit:
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info = v[2]
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self.assertEqual(info["generation"], 2)
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def testCollectGarbage(self):
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self.preclean()
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# Each of these cause four objects to be garbage: Two
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# Uncolectables and their instance dicts.
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Uncollectable()
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Uncollectable()
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C1055820(666)
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gc.collect()
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for v in self.visit:
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if v[1] != "stop":
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continue
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info = v[2]
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self.assertEqual(info["collected"], 2)
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self.assertEqual(info["uncollectable"], 8)
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# We should now have the Uncollectables in gc.garbage
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self.assertEqual(len(gc.garbage), 4)
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for e in gc.garbage:
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self.assertIsInstance(e, Uncollectable)
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# Now, let our callback handle the Uncollectable instances
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self.cleanup=True
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self.visit = []
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gc.garbage[:] = []
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gc.collect()
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for v in self.visit:
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if v[1] != "stop":
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continue
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info = v[2]
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self.assertEqual(info["collected"], 0)
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self.assertEqual(info["uncollectable"], 4)
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# Uncollectables should be gone
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self.assertEqual(len(gc.garbage), 0)
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class GCTogglingTests(unittest.TestCase):
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def setUp(self):
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gc.enable()
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@ -681,7 +815,7 @@ def test_main():
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try:
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gc.collect() # Delete 2nd generation garbage
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run_unittest(GCTests, GCTogglingTests)
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run_unittest(GCTests, GCTogglingTests, GCCallbackTests)
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finally:
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gc.set_debug(debug)
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# test gc.enable() even if GC is disabled by default
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@ -275,6 +275,9 @@ Library
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- Issue #14310: Sockets can now be with other processes on Windows using
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the api socket.socket.share() and socket.fromshare().
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- Issue #10576: The gc module now has a 'callbacks' member that will get
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called when garbage collection takes place.
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Build
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-----
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@ -65,14 +65,17 @@ static PyObject *garbage = NULL;
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/* Python string to use if unhandled exception occurs */
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static PyObject *gc_str = NULL;
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/* This is the number of objects who survived the last full collection. It
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/* a list of callbacks to be invoked when collection is performed */
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static PyObject *callbacks = NULL;
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/* This is the number of objects that survived the last full collection. It
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approximates the number of long lived objects tracked by the GC.
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(by "full collection", we mean a collection of the oldest generation).
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*/
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static Py_ssize_t long_lived_total = 0;
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/* This is the number of objects who survived all "non-full" collections,
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/* This is the number of objects that survived all "non-full" collections,
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and are awaiting to undergo a full collection for the first time.
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*/
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@ -787,7 +790,7 @@ get_time(void)
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/* This is the main function. Read this to understand how the
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* collection process works. */
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static Py_ssize_t
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collect(int generation)
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collect(int generation, Py_ssize_t *n_collected, Py_ssize_t *n_uncollectable)
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{
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int i;
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Py_ssize_t m = 0; /* # objects collected */
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@ -935,9 +938,64 @@ collect(int generation)
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PyErr_WriteUnraisable(gc_str);
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Py_FatalError("unexpected exception during garbage collection");
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}
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if (n_collected)
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*n_collected = m;
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if (n_uncollectable)
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*n_uncollectable = n;
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return n+m;
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}
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/* Invoke progress callbacks to notify clients that garbage collection
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* is starting or stopping
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*/
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static void
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invoke_gc_callback(const char *phase, int generation,
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Py_ssize_t collected, Py_ssize_t uncollectable)
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{
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Py_ssize_t i;
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PyObject *info = NULL;
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/* we may get called very early */
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if (callbacks == NULL)
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return;
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/* The local variable cannot be rebound, check it for sanity */
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assert(callbacks != NULL && PyList_CheckExact(callbacks));
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if (PyList_GET_SIZE(callbacks) != 0) {
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info = Py_BuildValue("{sisnsn}",
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"generation", generation,
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"collected", collected,
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"uncollectable", uncollectable);
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if (info == NULL) {
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PyErr_WriteUnraisable(NULL);
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return;
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}
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}
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for (i=0; i<PyList_GET_SIZE(callbacks); i++) {
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PyObject *r, *cb = PyList_GET_ITEM(callbacks, i);
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Py_INCREF(cb); /* make sure cb doesn't go away */
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r = PyObject_CallFunction(cb, "sO", phase, info);
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Py_XDECREF(r);
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if (r == NULL)
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PyErr_WriteUnraisable(cb);
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Py_DECREF(cb);
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}
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Py_XDECREF(info);
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}
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/* Perform garbage collection of a generation and invoke
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* progress callbacks.
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*/
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static Py_ssize_t
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collect_with_callback(int generation)
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{
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Py_ssize_t result, collected, uncollectable;
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invoke_gc_callback("start", generation, 0, 0);
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result = collect(generation, &collected, &uncollectable);
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invoke_gc_callback("stop", generation, collected, uncollectable);
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return result;
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}
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static Py_ssize_t
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collect_generations(void)
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{
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@ -956,7 +1014,7 @@ collect_generations(void)
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if (i == NUM_GENERATIONS - 1
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&& long_lived_pending < long_lived_total / 4)
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continue;
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n = collect(i);
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n = collect_with_callback(i);
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break;
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}
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}
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@ -1027,7 +1085,7 @@ gc_collect(PyObject *self, PyObject *args, PyObject *kws)
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n = 0; /* already collecting, don't do anything */
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else {
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collecting = 1;
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n = collect(genarg);
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n = collect_with_callback(genarg);
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collecting = 0;
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}
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@ -1320,6 +1378,15 @@ PyInit_gc(void)
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if (PyModule_AddObject(m, "garbage", garbage) < 0)
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return NULL;
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if (callbacks == NULL) {
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callbacks = PyList_New(0);
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if (callbacks == NULL)
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return NULL;
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}
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Py_INCREF(callbacks);
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if (PyModule_AddObject(m, "callbacks", callbacks) < 0)
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return NULL;
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/* Importing can't be done in collect() because collect()
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* can be called via PyGC_Collect() in Py_Finalize().
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* This wouldn't be a problem, except that <initialized> is
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@ -1352,7 +1419,7 @@ PyGC_Collect(void)
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n = 0; /* already collecting, don't do anything */
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else {
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collecting = 1;
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n = collect(NUM_GENERATIONS - 1);
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n = collect_with_callback(NUM_GENERATIONS - 1);
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collecting = 0;
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}
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@ -1389,6 +1456,7 @@ _PyGC_Fini(void)
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Py_XDECREF(bytes);
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}
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}
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Py_CLEAR(callbacks);
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}
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/* for debugging */
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