mirror of https://github.com/python/cpython
SF patch #947476: Apply freelist technique to lists
Re-use list object bodies. Saves calls to malloc() and free() for faster list instantiation and deallocation.
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@ -54,6 +54,9 @@ Core and builtins
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the overallocation is no more than three elements -- this improves space
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utilization for applications that have large numbers of small lists.
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- Most list bodies now get re-used rather than freed. Speeds up list
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instantiation and deletion by saving calls to malloc() and free().
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- The dict.update() method now accepts all the same argument forms
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as the dict() constructor. This now includes item lists and/or
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keyword arguments.
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@ -49,6 +49,11 @@ list_resize(PyListObject *self, int newsize)
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return 0;
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}
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/* Empty list reuse scheme to save calls to malloc and free */
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#define MAXFREELISTS 80
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static PyListObject *free_lists[MAXFREELISTS];
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static int num_free_lists = 0;
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PyObject *
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PyList_New(int size)
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{
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@ -63,9 +68,14 @@ PyList_New(int size)
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if (nbytes / sizeof(PyObject *) != (size_t)size) {
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return PyErr_NoMemory();
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}
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op = PyObject_GC_New(PyListObject, &PyList_Type);
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if (op == NULL) {
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return NULL;
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if (num_free_lists) {
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num_free_lists--;
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op = free_lists[num_free_lists];
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_Py_NewReference((PyObject *)op);
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} else {
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op = PyObject_GC_New(PyListObject, &PyList_Type);
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if (op == NULL)
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return NULL;
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}
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if (size <= 0) {
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op->ob_item = NULL;
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@ -233,7 +243,10 @@ list_dealloc(PyListObject *op)
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}
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PyMem_FREE(op->ob_item);
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}
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op->ob_type->tp_free((PyObject *)op);
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if (num_free_lists < MAXFREELISTS && PyList_CheckExact(op))
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free_lists[num_free_lists++] = op;
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else
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op->ob_type->tp_free((PyObject *)op);
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Py_TRASHCAN_SAFE_END(op)
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}
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