changegroup: sparsely populate fnodes
Previously, fnodes had a key and empty dict value for every element in
changedfiles. This is somewhat wasteful. Empty dicts in CPython consume
a lot more memory than you would expect - 280 bytes.
On mozilla-central, which has ~190,000 files/fnodes keys, the previous
loop populating fnodes allocated 91,924 KB of memory, most of that for
the empty dicts.
With this patch in place, our peak RSS during mozilla-central clone
drops:
before: 364,356 KB
after: 326,008 KB
delta: -38,348 KB
When combined with the previous patch, total peak RSS decrease is now
190,116 KB.
import os, __builtin__
from mercurial import util
def lowerwrap(scope, funcname):
f = getattr(scope, funcname)
def wrap(fname, *args, **kwargs):
d, base = os.path.split(fname)
try:
files = os.listdir(d or '.')
except OSError:
files = []
if base in files:
return f(fname, *args, **kwargs)
for fn in files:
if fn.lower() == base.lower():
return f(os.path.join(d, fn), *args, **kwargs)
return f(fname, *args, **kwargs)
scope.__dict__[funcname] = wrap
def normcase(path):
return path.lower()
os.path.normcase = normcase
for f in 'file open'.split():
lowerwrap(__builtin__, f)
for f in "chmod chown open lstat stat remove unlink".split():
lowerwrap(os, f)
for f in "exists lexists".split():
lowerwrap(os.path, f)
lowerwrap(util, 'posixfile')