hgdemandimport/demandimportpy2.py

perf: add command to benchmark bundle reading

Upcoming commits will be refactoring bundle2 I/O code.

This commit establishes a `hg perfbundleread` command that measures
how long it takes to read a bundle using various mechanisms.

As a baseline, here's output from an uncompressed bundle1
bundle of my Firefox repo (7,098,622,890 bytes):

! read(8k)
! wall 0.763481 comb 0.760000 user 0.160000 sys 0.600000 (best of 6)
! read(16k)
! wall 0.644512 comb 0.640000 user 0.110000 sys 0.530000 (best of 16)
! read(32k)
! wall 0.581172 comb 0.590000 user 0.060000 sys 0.530000 (best of 18)
! read(128k)
! wall 0.535183 comb 0.530000 user 0.010000 sys 0.520000 (best of 19)
! cg1 deltaiter()
! wall 0.873500 comb 0.880000 user 0.840000 sys 0.040000 (best of 12)
! cg1 getchunks()
! wall 6.283797 comb 6.270000 user 5.570000 sys 0.700000 (best of 3)
! cg1 read(8k)
! wall 1.097173 comb 1.100000 user 0.400000 sys 0.700000 (best of 10)
! cg1 read(16k)
! wall 0.810750 comb 0.800000 user 0.200000 sys 0.600000 (best of 13)
! cg1 read(32k)
! wall 0.671215 comb 0.670000 user 0.110000 sys 0.560000 (best of 15)
! cg1 read(128k)
! wall 0.597857 comb 0.600000 user 0.020000 sys 0.580000 (best of 15)

And from an uncompressed bundle2 bundle (6,070,036,163 bytes):

! read(8k)
! wall 0.676997 comb 0.680000 user 0.160000 sys 0.520000 (best of 15)
! read(16k)
! wall 0.592706 comb 0.590000 user 0.080000 sys 0.510000 (best of 17)
! read(32k)
! wall 0.529395 comb 0.530000 user 0.050000 sys 0.480000 (best of 16)
! read(128k)
! wall 0.491270 comb 0.490000 user 0.010000 sys 0.480000 (best of 19)
! bundle2 forwardchunks()
! wall 2.997131 comb 2.990000 user 2.270000 sys 0.720000 (best of 4)
! bundle2 iterparts()
! wall 12.247197 comb 10.670000 user 8.170000 sys 2.500000 (best of 3)
! bundle2 part seek()
! wall 11.761675 comb 10.500000 user 8.240000 sys 2.260000 (best of 3)
! bundle2 part read(8k)
! wall 9.116163 comb 9.110000 user 8.240000 sys 0.870000 (best of 3)
! bundle2 part read(16k)
! wall 8.984362 comb 8.970000 user 8.110000 sys 0.860000 (best of 3)
! bundle2 part read(32k)
! wall 8.758364 comb 8.740000 user 7.860000 sys 0.880000 (best of 3)
! bundle2 part read(128k)
! wall 8.749040 comb 8.730000 user 7.830000 sys 0.900000 (best of 3)

We already see some interesting data. Notably that bundle2 has
significant overhead compared to bundle1. This matters for e.g. stream
clone bundles, which can be applied at >1Gbps.

Differential Revision: https://phab.mercurial-scm.org/D1385

# demandimport.py - global demand-loading of modules for Mercurial
#
# Copyright 2006, 2007 Matt Mackall <[e-mail]>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.

'''
demandimport - automatic demandloading of modules

To enable this module, do:

  import demandimport; demandimport.enable()

Imports of the following forms will be demand-loaded:

  import a, b.c
  import a.b as c
  from a import b,c # a will be loaded immediately

These imports will not be delayed:

  from a import *
  b = __import__(a)
'''

from __future__ import absolute_import

import __builtin__ as builtins
import contextlib
import sys

contextmanager = contextlib.contextmanager

_origimport = __import__

nothing = object()

def _hgextimport(importfunc, name, globals, *args, **kwargs):
    try:
        return importfunc(name, globals, *args, **kwargs)
    except ImportError:
        if not globals:
            raise
        # extensions are loaded with "hgext_" prefix
        hgextname = 'hgext_%s' % name
        nameroot = hgextname.split('.', 1)[0]
        contextroot = globals.get('__name__', '').split('.', 1)[0]
        if nameroot != contextroot:
            raise
        # retry to import with "hgext_" prefix
        return importfunc(hgextname, globals, *args, **kwargs)

class _demandmod(object):
    """module demand-loader and proxy

    Specify 1 as 'level' argument at construction, to import module
    relatively.
    """

    def __init__(self, name, globals, locals, level):
        if '.' in name:
            head, rest = name.split('.', 1)
            after = [rest]
        else:
            head = name
            after = []
        object.__setattr__(self, r"_data",
                           (head, globals, locals, after, level, set()))
        object.__setattr__(self, r"_module", None)

    def _extend(self, name):
        """add to the list of submodules to load"""
        self._data[3].append(name)

    def _addref(self, name):
        """Record that the named module ``name`` imports this module.

        References to this proxy class having the name of this module will be
        replaced at module load time. We assume the symbol inside the importing
        module is identical to the "head" name of this module. We don't
        actually know if "as X" syntax is being used to change the symbol name
        because this information isn't exposed to __import__.
        """
        self._data[5].add(name)

    def _load(self):
        if not self._module:
            head, globals, locals, after, level, modrefs = self._data
            mod = _hgextimport(_origimport, head, globals, locals, None, level)
            if mod is self:
                # In this case, _hgextimport() above should imply
                # _demandimport(). Otherwise, _hgextimport() never
                # returns _demandmod. This isn't intentional behavior,
                # in fact. (see also issue5304 for detail)
                #
                # If self._module is already bound at this point, self
                # should be already _load()-ed while _hgextimport().
                # Otherwise, there is no way to import actual module
                # as expected, because (re-)invoking _hgextimport()
                # should cause same result.
                # This is reason why _load() returns without any more
                # setup but assumes self to be already bound.
                mod = self._module
                assert mod and mod is not self, "%s, %s" % (self, mod)
                return

            # load submodules
            def subload(mod, p):
                h, t = p, None
                if '.' in p:
                    h, t = p.split('.', 1)
                if getattr(mod, h, nothing) is nothing:
                    setattr(mod, h, _demandmod(p, mod.__dict__, mod.__dict__,
                                               level=1))
                elif t:
                    subload(getattr(mod, h), t)

            for x in after:
                subload(mod, x)

            # Replace references to this proxy instance with the actual module.
            if locals:
                if locals.get(head) is self:
                    locals[head] = mod
                elif locals.get(head + r'mod') is self:
                    locals[head + r'mod'] = mod

            for modname in modrefs:
                modref = sys.modules.get(modname, None)
                if modref and getattr(modref, head, None) is self:
                    setattr(modref, head, mod)

            object.__setattr__(self, r"_module", mod)

    def __repr__(self):
        if self._module:
            return "<proxied module '%s'>" % self._data[0]
        return "<unloaded module '%s'>" % self._data[0]

    def __call__(self, *args, **kwargs):
        raise TypeError("%s object is not callable" % repr(self))

    def __getattr__(self, attr):
        self._load()
        return getattr(self._module, attr)

    def __setattr__(self, attr, val):
        self._load()
        setattr(self._module, attr, val)

    @property
    def __dict__(self):
        self._load()
        return self._module.__dict__

    @property
    def __doc__(self):
        self._load()
        return self._module.__doc__

_pypy = '__pypy__' in sys.builtin_module_names

def _demandimport(name, globals=None, locals=None, fromlist=None, level=-1):
    if locals is None or name in ignore or fromlist == ('*',):
        # these cases we can't really delay
        return _hgextimport(_origimport, name, globals, locals, fromlist, level)
    elif not fromlist:
        # import a [as b]
        if '.' in name: # a.b
            base, rest = name.split('.', 1)
            # email.__init__ loading email.mime
            if globals and globals.get('__name__', None) == base:
                return _origimport(name, globals, locals, fromlist, level)
            # if a is already demand-loaded, add b to its submodule list
            if base in locals:
                if isinstance(locals[base], _demandmod):
                    locals[base]._extend(rest)
                return locals[base]
        return _demandmod(name, globals, locals, level)
    else:
        # There is a fromlist.
        # from a import b,c,d
        # from . import b,c,d
        # from .a import b,c,d

        # level == -1: relative and absolute attempted (Python 2 only).
        # level >= 0: absolute only (Python 2 w/ absolute_import and Python 3).
        # The modern Mercurial convention is to use absolute_import everywhere,
        # so modern Mercurial code will have level >= 0.

        # The name of the module the import statement is located in.
        globalname = globals.get('__name__')

        def processfromitem(mod, attr):
            """Process an imported symbol in the import statement.

            If the symbol doesn't exist in the parent module, and if the
            parent module is a package, it must be a module. We set missing
            modules up as _demandmod instances.
            """
            symbol = getattr(mod, attr, nothing)
            nonpkg = getattr(mod, '__path__', nothing) is nothing
            if symbol is nothing:
                if nonpkg:
                    # do not try relative import, which would raise ValueError,
                    # and leave unknown attribute as the default __import__()
                    # would do. the missing attribute will be detected later
                    # while processing the import statement.
                    return
                mn = '%s.%s' % (mod.__name__, attr)
                if mn in ignore:
                    importfunc = _origimport
                else:
                    importfunc = _demandmod
                symbol = importfunc(attr, mod.__dict__, locals, level=1)
                setattr(mod, attr, symbol)

            # Record the importing module references this symbol so we can
            # replace the symbol with the actual module instance at load
            # time.
            if globalname and isinstance(symbol, _demandmod):
                symbol._addref(globalname)

        def chainmodules(rootmod, modname):
            # recurse down the module chain, and return the leaf module
            mod = rootmod
            for comp in modname.split('.')[1:]:
                obj = getattr(mod, comp, nothing)
                if obj is nothing:
                    obj = _demandmod(comp, mod.__dict__, mod.__dict__, level=1)
                    setattr(mod, comp, obj)
                elif mod.__name__ + '.' + comp in sys.modules:
                    # prefer loaded module over attribute (issue5617)
                    obj = sys.modules[mod.__name__ + '.' + comp]
                mod = obj
            return mod

        if level >= 0:
            if name:
                # "from a import b" or "from .a import b" style
                rootmod = _hgextimport(_origimport, name, globals, locals,
                                       level=level)
                mod = chainmodules(rootmod, name)
            elif _pypy:
                # PyPy's __import__ throws an exception if invoked
                # with an empty name and no fromlist.  Recreate the
                # desired behaviour by hand.
                mn = globalname
                mod = sys.modules[mn]
                if getattr(mod, '__path__', nothing) is nothing:
                    mn = mn.rsplit('.', 1)[0]
                    mod = sys.modules[mn]
                if level > 1:
                    mn = mn.rsplit('.', level - 1)[0]
                    mod = sys.modules[mn]
            else:
                mod = _hgextimport(_origimport, name, globals, locals,
                                   level=level)

            for x in fromlist:
                processfromitem(mod, x)

            return mod

        # But, we still need to support lazy loading of standard library and 3rd
        # party modules. So handle level == -1.
        mod = _hgextimport(_origimport, name, globals, locals)
        mod = chainmodules(mod, name)

        for x in fromlist:
            processfromitem(mod, x)

        return mod

ignore = []

def init(ignorelist):
    global ignore
    ignore = ignorelist

def isenabled():
    return builtins.__import__ == _demandimport

def enable():
    "enable global demand-loading of modules"
    builtins.__import__ = _demandimport

def disable():
    "disable global demand-loading of modules"
    builtins.__import__ = _origimport

@contextmanager
def deactivated():
    "context manager for disabling demandimport in 'with' blocks"
    demandenabled = isenabled()
    if demandenabled:
        disable()

    try:
        yield
    finally:
        if demandenabled:
            enable()