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Issue #4688: Add a heuristic so that tuples and dicts containing only

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untrackable objects are not tracked by the garbage collector. This can
reduce the size of collections and therefore the garbage collection overhead
on long-running programs, depending on their particular use of datatypes.

(trivia: this makes the "binary_trees" benchmark from the Computer Language
Shootout 40% faster)
This commit is contained in:
Antoine Pitrou 2009-03-23 18:41:45 +00:00
parent e5b78563b6
commit f8387af262
11 changed files with 401 additions and 2 deletions
Download patch file Download diff file Expand all files Collapse all files

82
Objects/dictobject.c
View file

@ -180,6 +180,24 @@ show_alloc(void)
}
#endif
/* Debug statistic to count GC tracking of dicts */
#ifdef SHOW_TRACK_COUNT
static Py_ssize_t count_untracked = 0;
static Py_ssize_t count_tracked = 0;
static void
show_track(void)
{
fprintf(stderr, "Dicts created: %" PY_FORMAT_SIZE_T "d\n",
count_tracked + count_untracked);
fprintf(stderr, "Dicts tracked by the GC: %" PY_FORMAT_SIZE_T
"d\n", count_tracked);
fprintf(stderr, "%.2f%% dict tracking rate\n\n",
(100.0*count_tracked/(count_untracked+count_tracked)));
}
#endif
/* Initialization macros.
There are two ways to create a dict: PyDict_New() is the main C API
function, and the tp_new slot maps to dict_new(). In the latter case we
@ -232,6 +250,9 @@ PyDict_New(void)
#endif
#ifdef SHOW_ALLOC_COUNT
Py_AtExit(show_alloc);
#endif
#ifdef SHOW_TRACK_COUNT
Py_AtExit(show_track);
#endif
}
if (numfree) {
@ -262,10 +283,12 @@ PyDict_New(void)
#endif
}
mp->ma_lookup = lookdict_string;
#ifdef SHOW_TRACK_COUNT
count_untracked++;
#endif
#ifdef SHOW_CONVERSION_COUNTS
++created;
#endif
_PyObject_GC_TRACK(mp);
return (PyObject *)mp;
}
@ -433,6 +456,52 @@ lookdict_string(PyDictObject *mp, PyObject *key, register long hash)
return 0;
}
#ifdef SHOW_TRACK_COUNT
#define INCREASE_TRACK_COUNT \
(count_tracked++, count_untracked--);
#define DECREASE_TRACK_COUNT \
(count_tracked--, count_untracked++);
#else
#define INCREASE_TRACK_COUNT
#define DECREASE_TRACK_COUNT
#endif
#define MAINTAIN_TRACKING(mp, key, value) \
do { \
if (!_PyObject_GC_IS_TRACKED(mp)) { \
if (_PyObject_GC_MAY_BE_TRACKED(key) || \
_PyObject_GC_MAY_BE_TRACKED(value)) { \
_PyObject_GC_TRACK(mp); \
INCREASE_TRACK_COUNT \
} \
} \
} while(0)
void
_PyDict_MaybeUntrack(PyObject *op)
{
PyDictObject *mp;
PyObject *value;
Py_ssize_t mask, i;
PyDictEntry *ep;
if (!PyDict_CheckExact(op) || !_PyObject_GC_IS_TRACKED(op))
return;
mp = (PyDictObject *) op;
ep = mp->ma_table;
mask = mp->ma_mask;
for (i = 0; i <= mask; i++) {
if ((value = ep[i].me_value) == NULL)
continue;
if (_PyObject_GC_MAY_BE_TRACKED(value) ||
_PyObject_GC_MAY_BE_TRACKED(ep[i].me_key))
return;
}
_PyObject_GC_UNTRACK(op);
}
/*
Internal routine to insert a new item into the table.
Used both by the internal resize routine and by the public insert routine.
@ -453,6 +522,7 @@ insertdict(register PyDictObject *mp, PyObject *key, long hash, PyObject *value)
Py_DECREF(value);
return -1;
}
MAINTAIN_TRACKING(mp, key, value);
if (ep->me_value != NULL) {
old_value = ep->me_value;
ep->me_value = value;
@ -492,6 +562,7 @@ insertdict_clean(register PyDictObject *mp, PyObject *key, long hash,
PyDictEntry *ep0 = mp->ma_table;
register PyDictEntry *ep;
MAINTAIN_TRACKING(mp, key, value);
i = hash & mask;
ep = &ep0[i];
for (perturb = hash; ep->me_key != NULL; perturb >>= PERTURB_SHIFT) {
@ -2202,8 +2273,17 @@ dict_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
assert(d->ma_table == NULL && d->ma_fill == 0 && d->ma_used == 0);
INIT_NONZERO_DICT_SLOTS(d);
d->ma_lookup = lookdict_string;
/* The object has been implicitely tracked by tp_alloc */
if (type == &PyDict_Type)
_PyObject_GC_UNTRACK(d);
#ifdef SHOW_CONVERSION_COUNTS
++created;
#endif
#ifdef SHOW_TRACK_COUNT
if (_PyObject_GC_IS_TRACKED(d))
count_tracked++;
else
count_untracked++;
#endif
}
return self;