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).
#!/usr/bin/env python
from __future__ import absolute_import
__doc__ = """Same as `echo a >> b`, but ensures a changed mtime of b.
Without this svn will not detect workspace changes."""
import os
import sys
text = sys.argv[1]
fname = sys.argv[2]
f = open(fname, "ab")
try:
before = os.fstat(f.fileno()).st_mtime
f.write(text)
f.write("\n")
finally:
f.close()
inc = 1
now = os.stat(fname).st_mtime
while now == before:
t = now + inc
inc += 1
os.utime(fname, (t, t))
now = os.stat(fname).st_mtime