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store: don't read the whole fncache in memory...
store: don't read the whole fncache in memory In large repositories with lot of files, the fncache grows more than 100 MB and reading that whole thing into memory slows things down. Let's not read the whole thing into memory. This patch changes fncache loading code to read 1 MB at once. Loading 1 MB at once saves ~1 sec on perffncacheload for our internal repository. I tried various values such as 0.5 MB, 5 MB, 10 MB but best results were produced using 1 MB as the chunksize. On a narrow clone with fncache around 40 MB, this patch saves ~0.04 seconds on average on perffncacheload. To test the code, I have coded an extension in test-fncache.t which set chunksize to 1 byte, and the test passes with that. Differential Revision: https://phab.mercurial-scm.org/D5296

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_compat.py
90 lines | 2.8 KiB | text/x-python | PythonLexer
from __future__ import absolute_import, division, print_function
import sys
import types
PY2 = sys.version_info[0] == 2
if PY2:
from UserDict import IterableUserDict
# We 'bundle' isclass instead of using inspect as importing inspect is
# fairly expensive (order of 10-15 ms for a modern machine in 2016)
def isclass(klass):
return isinstance(klass, (type, types.ClassType))
# TYPE is used in exceptions, repr(int) is different on Python 2 and 3.
TYPE = "type"
def iteritems(d):
return d.iteritems()
def iterkeys(d):
return d.iterkeys()
# Python 2 is bereft of a read-only dict proxy, so we make one!
class ReadOnlyDict(IterableUserDict):
"""
Best-effort read-only dict wrapper.
"""
def __setitem__(self, key, val):
# We gently pretend we're a Python 3 mappingproxy.
raise TypeError("'mappingproxy' object does not support item "
"assignment")
def update(self, _):
# We gently pretend we're a Python 3 mappingproxy.
raise AttributeError("'mappingproxy' object has no attribute "
"'update'")
def __delitem__(self, _):
# We gently pretend we're a Python 3 mappingproxy.
raise TypeError("'mappingproxy' object does not support item "
"deletion")
def clear(self):
# We gently pretend we're a Python 3 mappingproxy.
raise AttributeError("'mappingproxy' object has no attribute "
"'clear'")
def pop(self, key, default=None):
# We gently pretend we're a Python 3 mappingproxy.
raise AttributeError("'mappingproxy' object has no attribute "
"'pop'")
def popitem(self):
# We gently pretend we're a Python 3 mappingproxy.
raise AttributeError("'mappingproxy' object has no attribute "
"'popitem'")
def setdefault(self, key, default=None):
# We gently pretend we're a Python 3 mappingproxy.
raise AttributeError("'mappingproxy' object has no attribute "
"'setdefault'")
def __repr__(self):
# Override to be identical to the Python 3 version.
return "mappingproxy(" + repr(self.data) + ")"
def metadata_proxy(d):
res = ReadOnlyDict()
res.data.update(d) # We blocked update, so we have to do it like this.
return res
else:
def isclass(klass):
return isinstance(klass, type)
TYPE = "class"
def iteritems(d):
return d.items()
def iterkeys(d):
return d.keys()
def metadata_proxy(d):
return types.MappingProxyType(dict(d))