Mercurial > hg
view mercurial/fancyopts.py @ 34824:e2ad93bcc084
revlog: introduce an experimental flag to slice chunks reads when too sparse
Delta chains can become quite sparse if there is a lot of unrelated data between
relevant pieces. Right now, revlog always reads all the necessary data for the
delta chain in one single read. This can lead to a lot of unrelated data to be
read (see issue5482 for more details).
One can use the `experimental.maxdeltachainspan` option with a large value
(or -1) to easily produce a very sparse delta chain.
This change introduces the ability to slice the chunks retrieval into multiple
reads, skipping large sections of unrelated data. Preliminary testing shows
interesting results. For example the peak memory consumption to read a manifest
on a large repository is reduced from 600MB to 250MB (200MB without
maxdeltachainspan). However, the slicing itself and the multiple reads can have
an negative impact on performance. This is why the new feature is hidden behind
an experimental flag.
Future changesets will add various parameters to control the slicing heuristics.
We hope to experiment a wide variety of repositories during 4.4 and hopefully
turn the feature on by default in 4.5.
As a first try, the algorithm itself is prone to deep changes. However, we wish
to define APIs and have a baseline to work on.
author | Paul Morelle <paul.morelle@octobus.net> |
---|---|
date | Tue, 10 Oct 2017 17:50:27 +0200 |
parents | db8531c45953 |
children | 898c6f812a51 |
line wrap: on
line source
# fancyopts.py - better command line parsing # # Copyright 2005-2009 Matt Mackall <mpm@selenic.com> and others # # 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 . import ( error, pycompat, ) # Set of flags to not apply boolean negation logic on nevernegate = { # avoid --no-noninteractive 'noninteractive', # These two flags are special because they cause hg to do one # thing and then exit, and so aren't suitable for use in things # like aliases anyway. 'help', 'version', } def gnugetopt(args, options, longoptions): """Parse options mostly like getopt.gnu_getopt. This is different from getopt.gnu_getopt in that an argument of - will become an argument of - instead of vanishing completely. """ extraargs = [] if '--' in args: stopindex = args.index('--') extraargs = args[stopindex + 1:] args = args[:stopindex] opts, parseargs = pycompat.getoptb(args, options, longoptions) args = [] while parseargs: arg = parseargs.pop(0) if arg and arg[0:1] == '-' and len(arg) > 1: parseargs.insert(0, arg) topts, newparseargs = pycompat.getoptb(parseargs,\ options, longoptions) opts = opts + topts parseargs = newparseargs else: args.append(arg) args.extend(extraargs) return opts, args def fancyopts(args, options, state, gnu=False): """ read args, parse options, and store options in state each option is a tuple of: short option or '' long option default value description option value label(optional) option types include: boolean or none - option sets variable in state to true string - parameter string is stored in state list - parameter string is added to a list integer - parameter strings is stored as int function - call function with parameter non-option args are returned """ namelist = [] shortlist = '' argmap = {} defmap = {} negations = {} alllong = set(o[1] for o in options) for option in options: if len(option) == 5: short, name, default, comment, dummy = option else: short, name, default, comment = option # convert opts to getopt format oname = name name = name.replace('-', '_') argmap['-' + short] = argmap['--' + oname] = name defmap[name] = default # copy defaults to state if isinstance(default, list): state[name] = default[:] elif callable(default): state[name] = None else: state[name] = default # does it take a parameter? if not (default is None or default is True or default is False): if short: short += ':' if oname: oname += '=' elif oname not in nevernegate: if oname.startswith('no-'): insert = oname[3:] else: insert = 'no-' + oname # backout (as a practical example) has both --commit and # --no-commit options, so we don't want to allow the # negations of those flags. if insert not in alllong: assert ('--' + oname) not in negations negations['--' + insert] = '--' + oname namelist.append(insert) if short: shortlist += short if name: namelist.append(oname) # parse arguments if gnu: parse = gnugetopt else: parse = pycompat.getoptb opts, args = parse(args, shortlist, namelist) # transfer result to state for opt, val in opts: boolval = True negation = negations.get(opt, False) if negation: opt = negation boolval = False name = argmap[opt] obj = defmap[name] t = type(obj) if callable(obj): state[name] = defmap[name](val) elif t is type(1): try: state[name] = int(val) except ValueError: raise error.Abort(_('invalid value %r for option %s, ' 'expected int') % (val, opt)) elif t is type(''): state[name] = val elif t is type([]): state[name].append(val) elif t is type(None) or t is type(False): state[name] = boolval # return unparsed args return args