hgdemandimport: apply lazy module loading to sys.meta_path finders
Python's `sys.meta_path` finders are the primary objects whose job it
is to find a module at import time. When `import` is called, Python
iterates objects in this list and calls `o.find_spec(...)` to find
a `ModuleSpec` (or None if the module couldn't be found by that
finder). If no meta path finder can find a module, import fails.
One of the default meta path finders is `PathFinder`. Its job is to
import modules from the filesystem and is probably the most important
importer. This finder looks at `sys.path` and `sys.path_hooks` to do
its job.
The `ModuleSpec` returned by `MetaPathImporter.find_spec()` has a
`loader` attribute, which defines the concrete module loader to use.
`sys.path_hooks` is a hook point for teaching `PathFinder` to
instantiate custom loader types.
Previously, we injected a custom `sys.path_hook` that told `PathFinder`
to wrap the default loaders with a loader that creates a module object
that is lazy.
This approach worked. But its main limitation was that it only applied
to the `PathFinder` meta path importer. There are other meta path
importers that are registered. And in the case of PyOxidizer loading
modules from memory, `PathFinder` doesn't come into play since
PyOxidizer's own meta path importer was handling all imports.
This commit changes our approach to lazy module loading by proxying
all meta path importers. Specifically, we overload the `find_spec()`
method to swap in a wrapped loader on the `ModuleSpec` before it
is returned. The end result of this is all meta path importers should
be lazy.
As much as I would have loved to utilize .__class__ manipulation to
achieve this, some meta path importers are implemented in C/Rust
in such a way that they cannot be monkeypatched. This is why we
use __getattribute__ to define a proxy.
Also, this change could theoretically open us up to regressions in
meta path importers whose loader is creating module objects which
can't be monkeypatched. But I'm not aware of any of these in the
wild. So I think we'll be safe.
According to hyperfine, this change yields a decent startup time win of
5-6ms:
```
Benchmark #1: ~/.pyenv/versions/3.6.10/bin/python ./hg version
Time (mean ± σ): 86.8 ms ± 0.5 ms [User: 78.0 ms, System: 8.7 ms]
Range (min … max): 86.0 ms … 89.1 ms 50 runs
Time (mean ± σ): 81.1 ms ± 2.7 ms [User: 74.5 ms, System: 6.5 ms]
Range (min … max): 77.8 ms … 90.5 ms 50 runs
Benchmark #2: ~/.pyenv/versions/3.7.6/bin/python ./hg version
Time (mean ± σ): 78.9 ms ± 0.6 ms [User: 70.2 ms, System: 8.7 ms]
Range (min … max): 78.1 ms … 81.2 ms 50 runs
Time (mean ± σ): 73.4 ms ± 0.6 ms [User: 65.3 ms, System: 8.0 ms]
Range (min … max): 72.4 ms … 75.7 ms 50 runs
Benchmark #3: ~/.pyenv/versions/3.8.1/bin/python ./hg version
Time (mean ± σ): 78.1 ms ± 0.6 ms [User: 70.2 ms, System: 7.9 ms]
Range (min … max): 77.4 ms … 80.9 ms 50 runs
Time (mean ± σ): 72.1 ms ± 0.4 ms [User: 64.4 ms, System: 7.6 ms]
Range (min … max): 71.4 ms … 74.1 ms 50 runs
```
Differential Revision: https://phab.mercurial-scm.org/D7954
# filesetlang.py - parser, tokenizer and utility for file set language
#
# Copyright 2010 Matt Mackall <mpm@selenic.com>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.
from __future__ import absolute_import
from .i18n import _
from .pycompat import getattr
from . import (
error,
parser,
pycompat,
)
# common weight constants for static optimization
# (see registrar.filesetpredicate for details)
WEIGHT_CHECK_FILENAME = 0.5
WEIGHT_READ_CONTENTS = 30
WEIGHT_STATUS = 10
WEIGHT_STATUS_THOROUGH = 50
elements = {
# token-type: binding-strength, primary, prefix, infix, suffix
b"(": (20, None, (b"group", 1, b")"), (b"func", 1, b")"), None),
b":": (15, None, None, (b"kindpat", 15), None),
b"-": (5, None, (b"negate", 19), (b"minus", 5), None),
b"not": (10, None, (b"not", 10), None, None),
b"!": (10, None, (b"not", 10), None, None),
b"and": (5, None, None, (b"and", 5), None),
b"&": (5, None, None, (b"and", 5), None),
b"or": (4, None, None, (b"or", 4), None),
b"|": (4, None, None, (b"or", 4), None),
b"+": (4, None, None, (b"or", 4), None),
b",": (2, None, None, (b"list", 2), None),
b")": (0, None, None, None, None),
b"symbol": (0, b"symbol", None, None, None),
b"string": (0, b"string", None, None, None),
b"end": (0, None, None, None, None),
}
keywords = {b'and', b'or', b'not'}
symbols = {}
globchars = b".*{}[]?/\\_"
def tokenize(program):
pos, l = 0, len(program)
program = pycompat.bytestr(program)
while pos < l:
c = program[pos]
if c.isspace(): # skip inter-token whitespace
pass
elif c in b"(),-:|&+!": # handle simple operators
yield (c, None, pos)
elif (
c in b'"\''
or c == b'r'
and program[pos : pos + 2] in (b"r'", b'r"')
): # handle quoted strings
if c == b'r':
pos += 1
c = program[pos]
decode = lambda x: x
else:
decode = parser.unescapestr
pos += 1
s = pos
while pos < l: # find closing quote
d = program[pos]
if d == b'\\': # skip over escaped characters
pos += 2
continue
if d == c:
yield (b'string', decode(program[s:pos]), s)
break
pos += 1
else:
raise error.ParseError(_(b"unterminated string"), s)
elif c.isalnum() or c in globchars or ord(c) > 127:
# gather up a symbol/keyword
s = pos
pos += 1
while pos < l: # find end of symbol
d = program[pos]
if not (d.isalnum() or d in globchars or ord(d) > 127):
break
pos += 1
sym = program[s:pos]
if sym in keywords: # operator keywords
yield (sym, None, s)
else:
yield (b'symbol', sym, s)
pos -= 1
else:
raise error.ParseError(_(b"syntax error"), pos)
pos += 1
yield (b'end', None, pos)
def parse(expr):
p = parser.parser(elements)
tree, pos = p.parse(tokenize(expr))
if pos != len(expr):
raise error.ParseError(_(b"invalid token"), pos)
return parser.simplifyinfixops(tree, {b'list', b'or'})
def getsymbol(x):
if x and x[0] == b'symbol':
return x[1]
raise error.ParseError(_(b'not a symbol'))
def getstring(x, err):
if x and (x[0] == b'string' or x[0] == b'symbol'):
return x[1]
raise error.ParseError(err)
def getkindpat(x, y, allkinds, err):
kind = getsymbol(x)
pat = getstring(y, err)
if kind not in allkinds:
raise error.ParseError(_(b"invalid pattern kind: %s") % kind)
return b'%s:%s' % (kind, pat)
def getpattern(x, allkinds, err):
if x and x[0] == b'kindpat':
return getkindpat(x[1], x[2], allkinds, err)
return getstring(x, err)
def getlist(x):
if not x:
return []
if x[0] == b'list':
return list(x[1:])
return [x]
def getargs(x, min, max, err):
l = getlist(x)
if len(l) < min or len(l) > max:
raise error.ParseError(err)
return l
def _analyze(x):
if x is None:
return x
op = x[0]
if op in {b'string', b'symbol'}:
return x
if op == b'kindpat':
getsymbol(x[1]) # kind must be a symbol
t = _analyze(x[2])
return (op, x[1], t)
if op == b'group':
return _analyze(x[1])
if op == b'negate':
raise error.ParseError(_(b"can't use negate operator in this context"))
if op == b'not':
t = _analyze(x[1])
return (op, t)
if op == b'and':
ta = _analyze(x[1])
tb = _analyze(x[2])
return (op, ta, tb)
if op == b'minus':
return _analyze((b'and', x[1], (b'not', x[2])))
if op in {b'list', b'or'}:
ts = tuple(_analyze(y) for y in x[1:])
return (op,) + ts
if op == b'func':
getsymbol(x[1]) # function name must be a symbol
ta = _analyze(x[2])
return (op, x[1], ta)
raise error.ProgrammingError(b'invalid operator %r' % op)
def _insertstatushints(x):
"""Insert hint nodes where status should be calculated (first path)
This works in bottom-up way, summing up status names and inserting hint
nodes at 'and' and 'or' as needed. Thus redundant hint nodes may be left.
Returns (status-names, new-tree) at the given subtree, where status-names
is a sum of status names referenced in the given subtree.
"""
if x is None:
return (), x
op = x[0]
if op in {b'string', b'symbol', b'kindpat'}:
return (), x
if op == b'not':
h, t = _insertstatushints(x[1])
return h, (op, t)
if op == b'and':
ha, ta = _insertstatushints(x[1])
hb, tb = _insertstatushints(x[2])
hr = ha + hb
if ha and hb:
return hr, (b'withstatus', (op, ta, tb), (b'string', b' '.join(hr)))
return hr, (op, ta, tb)
if op == b'or':
hs, ts = zip(*(_insertstatushints(y) for y in x[1:]))
hr = sum(hs, ())
if sum(bool(h) for h in hs) > 1:
return hr, (b'withstatus', (op,) + ts, (b'string', b' '.join(hr)))
return hr, (op,) + ts
if op == b'list':
hs, ts = zip(*(_insertstatushints(y) for y in x[1:]))
return sum(hs, ()), (op,) + ts
if op == b'func':
f = getsymbol(x[1])
# don't propagate 'ha' crossing a function boundary
ha, ta = _insertstatushints(x[2])
if getattr(symbols.get(f), '_callstatus', False):
return (f,), (b'withstatus', (op, x[1], ta), (b'string', f))
return (), (op, x[1], ta)
raise error.ProgrammingError(b'invalid operator %r' % op)
def _mergestatushints(x, instatus):
"""Remove redundant status hint nodes (second path)
This is the top-down path to eliminate inner hint nodes.
"""
if x is None:
return x
op = x[0]
if op == b'withstatus':
if instatus:
# drop redundant hint node
return _mergestatushints(x[1], instatus)
t = _mergestatushints(x[1], instatus=True)
return (op, t, x[2])
if op in {b'string', b'symbol', b'kindpat'}:
return x
if op == b'not':
t = _mergestatushints(x[1], instatus)
return (op, t)
if op == b'and':
ta = _mergestatushints(x[1], instatus)
tb = _mergestatushints(x[2], instatus)
return (op, ta, tb)
if op in {b'list', b'or'}:
ts = tuple(_mergestatushints(y, instatus) for y in x[1:])
return (op,) + ts
if op == b'func':
# don't propagate 'instatus' crossing a function boundary
ta = _mergestatushints(x[2], instatus=False)
return (op, x[1], ta)
raise error.ProgrammingError(b'invalid operator %r' % op)
def analyze(x):
"""Transform raw parsed tree to evaluatable tree which can be fed to
optimize() or getmatch()
All pseudo operations should be mapped to real operations or functions
defined in methods or symbols table respectively.
"""
t = _analyze(x)
_h, t = _insertstatushints(t)
return _mergestatushints(t, instatus=False)
def _optimizeandops(op, ta, tb):
if tb is not None and tb[0] == b'not':
return (b'minus', ta, tb[1])
return (op, ta, tb)
def _optimizeunion(xs):
# collect string patterns so they can be compiled into a single regexp
ws, ts, ss = [], [], []
for x in xs:
w, t = _optimize(x)
if t is not None and t[0] in {b'string', b'symbol', b'kindpat'}:
ss.append(t)
continue
ws.append(w)
ts.append(t)
if ss:
ws.append(WEIGHT_CHECK_FILENAME)
ts.append((b'patterns',) + tuple(ss))
return ws, ts
def _optimize(x):
if x is None:
return 0, x
op = x[0]
if op == b'withstatus':
w, t = _optimize(x[1])
return w, (op, t, x[2])
if op in {b'string', b'symbol'}:
return WEIGHT_CHECK_FILENAME, x
if op == b'kindpat':
w, t = _optimize(x[2])
return w, (op, x[1], t)
if op == b'not':
w, t = _optimize(x[1])
return w, (op, t)
if op == b'and':
wa, ta = _optimize(x[1])
wb, tb = _optimize(x[2])
if wa <= wb:
return wa, _optimizeandops(op, ta, tb)
else:
return wb, _optimizeandops(op, tb, ta)
if op == b'or':
ws, ts = _optimizeunion(x[1:])
if len(ts) == 1:
return ws[0], ts[0] # 'or' operation is fully optimized out
ts = tuple(
it[1] for it in sorted(enumerate(ts), key=lambda it: ws[it[0]])
)
return max(ws), (op,) + ts
if op == b'list':
ws, ts = zip(*(_optimize(y) for y in x[1:]))
return sum(ws), (op,) + ts
if op == b'func':
f = getsymbol(x[1])
w = getattr(symbols.get(f), '_weight', 1)
wa, ta = _optimize(x[2])
return w + wa, (op, x[1], ta)
raise error.ProgrammingError(b'invalid operator %r' % op)
def optimize(x):
"""Reorder/rewrite evaluatable tree for optimization
All pseudo operations should be transformed beforehand.
"""
_w, t = _optimize(x)
return t
def prettyformat(tree):
return parser.prettyformat(tree, (b'string', b'symbol'))