[PATCH 6 of 6] dirs: use mutable strings internally
Bryan O'Sullivan
bos at serpentine.com
Mon Apr 1 15:49:19 CDT 2013
# HG changeset patch
# User Bryan O'Sullivan <bryano at fb.com>
# Date 1364849337 25200
# Mon Apr 01 13:48:57 2013 -0700
# Node ID 65a67c7aefed9d86aa24758aaa7529445856db9f
# Parent 34666bf45a79c688f24fe15ce6a73894a6adfee6
dirs: use mutable strings internally
perfdirs results for a working dir with 170,000 files:
Python 638 msec
C 244
C+int 192
C+int+str 168
In the large repo above, the nearly 0.5 second time improvement is
visible in commands like "hg add" and "hg update".
hg add
Python 1100 msec
C+int+str 600
hg update (with nothing to do)
Python 2800 msec
C+int+str 2240
diff --git a/mercurial/dirs.c b/mercurial/dirs.c
--- a/mercurial/dirs.c
+++ b/mercurial/dirs.c
@@ -16,6 +16,9 @@
*
* We modify Python integers for refcounting, but those integers are
* never visible to Python code.
+ *
+ * We mutate strings in-place, but leave them immutable once they can
+ * be seen by Python code.
*/
typedef struct {
@@ -38,6 +41,7 @@ static inline Py_ssize_t _finddir(PyObje
static int _addpath(PyObject *dirs, PyObject *path)
{
+ const char *cpath = PyString_AS_STRING(path);
Py_ssize_t pos = PyString_GET_SIZE(path);
PyObject *key = NULL;
int ret = -1;
@@ -45,15 +49,24 @@ static int _addpath(PyObject *dirs, PyOb
while ((pos = _finddir(path, pos - 1)) != -1) {
PyObject *val;
- key = PyString_FromStringAndSize(PyString_AS_STRING(path), pos);
-
- if (key == NULL)
- goto bail;
+ /* It's likely that every prefix already has an entry
+ in our dict. Try to avoid allocating and
+ deallocating a string for each prefix we check. */
+ if (key != NULL)
+ ((PyStringObject *)key)->ob_shash = -1;
+ else {
+ /* Force Python to not reuse a small shared string. */
+ key = PyString_FromStringAndSize(cpath,
+ pos < 2 ? 2 : pos);
+ if (key == NULL)
+ goto bail;
+ }
+ PyString_GET_SIZE(key) = pos;
+ PyString_AS_STRING(key)[pos] = '\0';
val = PyDict_GetItem(dirs, key);
if (val != NULL) {
PyInt_AS_LONG(val) += 1;
- Py_CLEAR(key);
continue;
}
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