Mercurial > public > mercurial-scm > hg
view mercurial/lsprof.py @ 44118:f81c17ec303c
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 ? ?): 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 ? ?): 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 ? ?): 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 ? ?): 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 ? ?): 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 ? ?): 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
author | Gregory Szorc <gregory.szorc@gmail.com> |
---|---|
date | Mon, 20 Jan 2020 23:51:25 -0800 |
parents | 9f70512ae2cf |
children | 6000f5b25c9b |
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from __future__ import absolute_import, print_function import _lsprof import sys from .pycompat import getattr from . import pycompat Profiler = _lsprof.Profiler # PyPy doesn't expose profiler_entry from the module. profiler_entry = getattr(_lsprof, 'profiler_entry', None) __all__ = [b'profile', b'Stats'] def profile(f, *args, **kwds): """XXX docstring""" p = Profiler() p.enable(subcalls=True, builtins=True) try: f(*args, **kwds) finally: p.disable() return Stats(p.getstats()) class Stats(object): """XXX docstring""" def __init__(self, data): self.data = data def sort(self, crit="inlinetime"): """XXX docstring""" # profiler_entries isn't defined when running under PyPy. if profiler_entry: if crit not in profiler_entry.__dict__: raise ValueError(b"Can't sort by %s" % crit) elif self.data and not getattr(self.data[0], crit, None): raise ValueError(b"Can't sort by %s" % crit) self.data.sort(key=lambda x: getattr(x, crit), reverse=True) for e in self.data: if e.calls: e.calls.sort(key=lambda x: getattr(x, crit), reverse=True) def pprint(self, top=None, file=None, limit=None, climit=None): """XXX docstring""" if file is None: file = sys.stdout d = self.data if top is not None: d = d[:top] cols = b"% 12d %12d %11.4f %11.4f %s\n" hcols = b"% 12s %12s %12s %12s %s\n" file.write( hcols % ( b"CallCount", b"Recursive", b"Total(s)", b"Inline(s)", b"module:lineno(function)", ) ) count = 0 for e in d: file.write( cols % ( e.callcount, e.reccallcount, e.totaltime, e.inlinetime, label(e.code), ) ) count += 1 if limit is not None and count == limit: return ccount = 0 if climit and e.calls: for se in e.calls: file.write( cols % ( se.callcount, se.reccallcount, se.totaltime, se.inlinetime, b" %s" % label(se.code), ) ) count += 1 ccount += 1 if limit is not None and count == limit: return if climit is not None and ccount == climit: break def freeze(self): """Replace all references to code objects with string descriptions; this makes it possible to pickle the instance.""" # this code is probably rather ickier than it needs to be! for i in range(len(self.data)): e = self.data[i] if not isinstance(e.code, str): self.data[i] = type(e)((label(e.code),) + e[1:]) if e.calls: for j in range(len(e.calls)): se = e.calls[j] if not isinstance(se.code, str): e.calls[j] = type(se)((label(se.code),) + se[1:]) _fn2mod = {} def label(code): if isinstance(code, str): if sys.version_info.major >= 3: code = code.encode('latin-1') return code try: mname = _fn2mod[code.co_filename] except KeyError: for k, v in list(pycompat.iteritems(sys.modules)): if v is None: continue if not isinstance(getattr(v, '__file__', None), str): continue if v.__file__.startswith(code.co_filename): mname = _fn2mod[code.co_filename] = k break else: mname = _fn2mod[code.co_filename] = '<%s>' % code.co_filename res = '%s:%d(%s)' % (mname, code.co_firstlineno, code.co_name) if sys.version_info.major >= 3: res = res.encode('latin-1') return res