[Python-checkins] bpo-31558: Add gc.freeze() (#3705)
Łukasz Langa
webhook-mailer at python.org
Mon Oct 16 15:49:47 EDT 2017
https://github.com/python/cpython/commit/c75edabbb65ca2bb29e51f8d1eb2c780e5890982
commit: c75edabbb65ca2bb29e51f8d1eb2c780e5890982
branch: master
author: brainfvck <li.zekun at gmail.com>
committer: Łukasz Langa <lukasz at langa.pl>
date: 2017-10-16T12:49:41-07:00
summary:
bpo-31558: Add gc.freeze() (#3705)
Freeze all the objects tracked by gc - move them to a permanent generation
and ignore all the future collections. This can be used before a POSIX
fork() call to make the gc copy-on-write friendly or to speed up collection.
files:
M Doc/library/gc.rst
M Include/internal/mem.h
M Lib/test/test_gc.py
M Modules/clinic/gcmodule.c.h
M Modules/gcmodule.c
diff --git a/Doc/library/gc.rst b/Doc/library/gc.rst
index 87d682445ba..153d8fb7045 100644
--- a/Doc/library/gc.rst
+++ b/Doc/library/gc.rst
@@ -174,6 +174,33 @@ The :mod:`gc` module provides the following functions:
.. versionadded:: 3.1
+.. function:: freeze()
+
+ Freeze all the objects tracked by gc - move them to a permanent generation
+ and ignore all the future collections. This can be used before a POSIX
+ fork() call to make the gc copy-on-write friendly or to speed up collection.
+ Also collection before a POSIX fork() call may free pages for future
+ allocation which can cause copy-on-write too so it's advised to disable gc
+ in master process and freeze before fork and enable gc in child process.
+
+ .. versionadded:: 3.7
+
+
+.. function:: unfreeze()
+
+ Unfreeze the objects in the permanent generation, put them back into the
+ oldest generation.
+
+ .. versionadded:: 3.7
+
+
+.. function:: get_freeze_count()
+
+ Return the number of objects in the permanent generation.
+
+ .. versionadded:: 3.7
+
+
The following variables are provided for read-only access (you can mutate the
values but should not rebind them):
diff --git a/Include/internal/mem.h b/Include/internal/mem.h
index f3a8f56e805..471cdf45df2 100644
--- a/Include/internal/mem.h
+++ b/Include/internal/mem.h
@@ -167,6 +167,8 @@ struct _gc_runtime_state {
/* linked lists of container objects */
struct gc_generation generations[NUM_GENERATIONS];
PyGC_Head *generation0;
+ /* a permanent generation which won't be collected */
+ struct gc_generation permanent_generation;
struct gc_generation_stats generation_stats[NUM_GENERATIONS];
/* true if we are currently running the collector */
int collecting;
diff --git a/Lib/test/test_gc.py b/Lib/test/test_gc.py
index 914efec3d3e..904fc7d88c0 100644
--- a/Lib/test/test_gc.py
+++ b/Lib/test/test_gc.py
@@ -734,6 +734,12 @@ def test_get_stats(self):
self.assertEqual(new[1]["collections"], old[1]["collections"])
self.assertEqual(new[2]["collections"], old[2]["collections"] + 1)
+ def test_freeze(self):
+ gc.freeze()
+ self.assertGreater(gc.get_freeze_count(), 0)
+ gc.unfreeze()
+ self.assertEqual(gc.get_freeze_count(), 0)
+
class GCCallbackTests(unittest.TestCase):
def setUp(self):
diff --git a/Modules/clinic/gcmodule.c.h b/Modules/clinic/gcmodule.c.h
index 771c57387bb..c31ef65eb06 100644
--- a/Modules/clinic/gcmodule.c.h
+++ b/Modules/clinic/gcmodule.c.h
@@ -255,4 +255,74 @@ PyDoc_STRVAR(gc_is_tracked__doc__,
#define GC_IS_TRACKED_METHODDEF \
{"is_tracked", (PyCFunction)gc_is_tracked, METH_O, gc_is_tracked__doc__},
-/*[clinic end generated code: output=5a58583f00ab018e input=a9049054013a1b77]*/
+
+PyDoc_STRVAR(gc_freeze__doc__,
+"freeze($module, /)\n"
+"--\n"
+"\n"
+"Freeze all current tracked objects and ignore them for future collections.\n"
+"\n"
+"This can be used before a POSIX fork() call to make the gc copy-on-write friendly.\n"
+"Note: collection before a POSIX fork() call may free pages for future allocation\n"
+"which can cause copy-on-write.");
+
+#define GC_FREEZE_METHODDEF \
+ {"freeze", (PyCFunction)gc_freeze, METH_NOARGS, gc_freeze__doc__},
+
+static PyObject *
+gc_freeze_impl(PyObject *module);
+
+static PyObject *
+gc_freeze(PyObject *module, PyObject *Py_UNUSED(ignored))
+{
+ return gc_freeze_impl(module);
+}
+
+PyDoc_STRVAR(gc_unfreeze__doc__,
+"unfreeze($module, /)\n"
+"--\n"
+"\n"
+"Unfreeze all objects in the permanent generation.\n"
+"\n"
+"Put all objects in the permanent generation back into oldest generation.");
+
+#define GC_UNFREEZE_METHODDEF \
+ {"unfreeze", (PyCFunction)gc_unfreeze, METH_NOARGS, gc_unfreeze__doc__},
+
+static PyObject *
+gc_unfreeze_impl(PyObject *module);
+
+static PyObject *
+gc_unfreeze(PyObject *module, PyObject *Py_UNUSED(ignored))
+{
+ return gc_unfreeze_impl(module);
+}
+
+PyDoc_STRVAR(gc_get_freeze_count__doc__,
+"get_freeze_count($module, /)\n"
+"--\n"
+"\n"
+"Return the number of objects in the permanent generation.");
+
+#define GC_GET_FREEZE_COUNT_METHODDEF \
+ {"get_freeze_count", (PyCFunction)gc_get_freeze_count, METH_NOARGS, gc_get_freeze_count__doc__},
+
+static int
+gc_get_freeze_count_impl(PyObject *module);
+
+static PyObject *
+gc_get_freeze_count(PyObject *module, PyObject *Py_UNUSED(ignored))
+{
+ PyObject *return_value = NULL;
+ int _return_value;
+
+ _return_value = gc_get_freeze_count_impl(module);
+ if ((_return_value == -1) && PyErr_Occurred()) {
+ goto exit;
+ }
+ return_value = PyLong_FromLong((long)_return_value);
+
+exit:
+ return return_value;
+}
+/*[clinic end generated code: output=4f41ec4588154f2b input=a9049054013a1b77]*/
diff --git a/Modules/gcmodule.c b/Modules/gcmodule.c
index 832e27ebe66..6e26c7a68f6 100644
--- a/Modules/gcmodule.c
+++ b/Modules/gcmodule.c
@@ -71,6 +71,10 @@ _PyGC_Initialize(struct _gc_runtime_state *state)
state->generations[i] = generations[i];
};
state->generation0 = GEN_HEAD(0);
+ struct gc_generation permanent_generation = {
+ {{&state->permanent_generation.head, &state->permanent_generation.head, 0}}, 0, 0
+ };
+ state->permanent_generation = permanent_generation;
}
/*--------------------------------------------------------------------------
@@ -813,6 +817,8 @@ collect(int generation, Py_ssize_t *n_collected, Py_ssize_t *n_uncollectable,
for (i = 0; i < NUM_GENERATIONS; i++)
PySys_FormatStderr(" %zd",
gc_list_size(GEN_HEAD(i)));
+ PySys_WriteStderr("\ngc: objects in permanent generation: %zd",
+ gc_list_size(&_PyRuntime.gc.permanent_generation.head));
t1 = _PyTime_GetMonotonicClock();
PySys_WriteStderr("\n");
@@ -1405,6 +1411,56 @@ gc_is_tracked(PyObject *module, PyObject *obj)
return result;
}
+/*[clinic input]
+gc.freeze
+
+Freeze all current tracked objects and ignore them for future collections.
+
+This can be used before a POSIX fork() call to make the gc copy-on-write friendly.
+Note: collection before a POSIX fork() call may free pages for future allocation
+which can cause copy-on-write.
+[clinic start generated code]*/
+
+static PyObject *
+gc_freeze_impl(PyObject *module)
+/*[clinic end generated code: output=502159d9cdc4c139 input=b602b16ac5febbe5]*/
+{
+ for (int i = 0; i < NUM_GENERATIONS; ++i) {
+ gc_list_merge(GEN_HEAD(i), &_PyRuntime.gc.permanent_generation.head);
+ _PyRuntime.gc.generations[i].count = 0;
+ }
+ Py_RETURN_NONE;
+}
+
+/*[clinic input]
+gc.unfreeze
+
+Unfreeze all objects in the permanent generation.
+
+Put all objects in the permanent generation back into oldest generation.
+[clinic start generated code]*/
+
+static PyObject *
+gc_unfreeze_impl(PyObject *module)
+/*[clinic end generated code: output=1c15f2043b25e169 input=2dd52b170f4cef6c]*/
+{
+ gc_list_merge(&_PyRuntime.gc.permanent_generation.head, GEN_HEAD(NUM_GENERATIONS-1));
+ Py_RETURN_NONE;
+}
+
+/*[clinic input]
+gc.get_freeze_count -> int
+
+Return the number of objects in the permanent generation.
+[clinic start generated code]*/
+
+static int
+gc_get_freeze_count_impl(PyObject *module)
+/*[clinic end generated code: output=e4e2ebcc77e5cbf3 input=4b759db880a3c6e4]*/
+{
+ return gc_list_size(&_PyRuntime.gc.permanent_generation.head);
+}
+
PyDoc_STRVAR(gc__doc__,
"This module provides access to the garbage collector for reference cycles.\n"
@@ -1422,7 +1478,10 @@ PyDoc_STRVAR(gc__doc__,
"get_objects() -- Return a list of all objects tracked by the collector.\n"
"is_tracked() -- Returns true if a given object is tracked.\n"
"get_referrers() -- Return the list of objects that refer to an object.\n"
-"get_referents() -- Return the list of objects that an object refers to.\n");
+"get_referents() -- Return the list of objects that an object refers to.\n"
+"freeze() -- Freeze all tracked objects and ignore them for future collections.\n"
+"unfreeze() -- Unfreeze all objects in the permanent generation.\n"
+"get_freeze_count() -- Return the number of objects in the permanent generation.\n");
static PyMethodDef GcMethods[] = {
GC_ENABLE_METHODDEF
@@ -1441,6 +1500,9 @@ static PyMethodDef GcMethods[] = {
gc_get_referrers__doc__},
{"get_referents", gc_get_referents, METH_VARARGS,
gc_get_referents__doc__},
+ GC_FREEZE_METHODDEF
+ GC_UNFREEZE_METHODDEF
+ GC_GET_FREEZE_COUNT_METHODDEF
{NULL, NULL} /* Sentinel */
};
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