[PATCH 01 of 11] bdiff: use Python memory allocator in fixws

[Gregory Szorc]

# HG changeset patch
# User Gregory Szorc <gregory.szorc at gmail.com>
# Date 1489089265 28800
#      Thu Mar 09 11:54:25 2017 -0800
# Node ID 7a8ce919a13a9ff6e73f391fe14d228e18387f15
# Parent  1871a1ee64ed49172b1568b89cdbab126284b309
bdiff: use Python memory allocator in fixws

Python has its own memory allocation APIs. For allocations
<= 512 bytes, it allocates memory from arenas. This means that
average small allocations don't call the system allocator, which
makes them faster. Also, arena allocations cut down on memory
fragmentation, which can matter for performance in long-running
processes.

Another advantage of using the Python memory allocator is that
allocations are tracked by Python. This is a bigger deal in
Python 3, as modern versions of Python have some decent built-in
tools for examining memory usage, leaks, etc.

This patch converts a trivial malloc() + free() in the bdiff code
to use the Python allocator APIs. Since the object being
operated on is a line, chances are it will use an arena. So,
this could have a net positive impact on performance (although
I didn't measure it).

diff --git a/mercurial/bdiff_module.c b/mercurial/bdiff_module.c
--- a/mercurial/bdiff_module.c
+++ b/mercurial/bdiff_module.c
@@ -158,7 +158,7 @@ static PyObject *fixws(PyObject *self, P
 	r = PyBytes_AsString(s);
 	rlen = PyBytes_Size(s);
 
-	w = (char *)malloc(rlen ? rlen : 1);
+	w = (char *)PyMem_Malloc(rlen ? rlen : 1);
 	if (!w)
 		goto nomem;
 
@@ -178,7 +178,7 @@ static PyObject *fixws(PyObject *self, P
 	result = PyBytes_FromStringAndSize(w, wlen);
 
 nomem:
-	free(w);
+	PyMem_Free(w);
 	return result ? result : PyErr_NoMemory();
 }