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view mercurial/rewriteutil.py @ 42743:8c9a6adec67a
rust-discovery: using the children cache in add_missing
The DAG range computation often needs to get back to very old
revisions, and turns out to be disproportionately long, given
that the end goal is to remove the descendents of the given
missing revisons from the undecided set.
The fast iteration capabilities available in the Rust case make
it possible to avoid the DAG range entirely, at the cost of
precomputing the children cache, and to simply iterate on
children of the given missing revisions.
This is a case where staying on the same side of the interface
between the two languages has clear benefits.
On discoveries with initial undecided sets
small enough to bypass sampling entirely, the total cost of
computing the children cache and the subsequent iteration
becomes better than the Python + C counterpart, which relies on
reachableroots2.
For example, on a repo with more than one million revisions with
an initial undecided set of 11 elements, we get these figures:
Rust version with simple iteration
addcommons: 57.287us
first undecided computation: 184.278334ms
first children cache computation: 131.056us
addmissings iteration: 42.766us
first addinfo total: 185.24 ms
Python + C version
first addcommons: 0.29 ms
addcommons 0.21 ms
first undecided computation 191.35 ms
addmissings 45.75 ms
first addinfo total: 237.77 ms
On discoveries with large undecided sets, the initial price paid
makes the first addinfo slower than the Python + C version,
but that's more than compensated by the gain in sampling and
subsequent iterations.
Here's an extreme example with an undecided set of a million revisions:
Rust version:
first undecided computation: 293.842629ms
first children cache computation: 407.911297ms
addmissings iteration: 34.312869ms
first addinfo total: 776.02 ms
taking initial sample
query 2: sampling time: 1318.38 ms
query 2; still undecided: 1005013, sample size is: 200
addmissings: 143.062us
Python + C version:
first undecided computation 298.13 ms
addmissings 80.13 ms
first addinfo total: 399.62 ms
taking initial sample
query 2: sampling time: 3957.23 ms
query 2; still undecided: 1005013, sample size is: 200
addmissings 52.88 ms
Differential Revision: https://phab.mercurial-scm.org/D6428
author | Georges Racinet <georges.racinet@octobus.net> |
---|---|
date | Tue, 16 Apr 2019 01:16:39 +0200 |
parents | 8c6329fa6038 |
children | 57875cf423c9 |
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# rewriteutil.py - utility functions for rewriting changesets # # Copyright 2017 Octobus <contact@octobus.net> # # 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, node, obsolete, revset, ) def precheck(repo, revs, action='rewrite'): """check if revs can be rewritten action is used to control the error message. Make sure this function is called after taking the lock. """ if node.nullrev in revs: msg = _("cannot %s null changeset") % (action) hint = _("no changeset checked out") raise error.Abort(msg, hint=hint) if len(repo[None].parents()) > 1: raise error.Abort(_("cannot %s while merging") % action) publicrevs = repo.revs('%ld and public()', revs) if publicrevs: msg = _("cannot %s public changesets") % (action) hint = _("see 'hg help phases' for details") raise error.Abort(msg, hint=hint) newunstable = disallowednewunstable(repo, revs) if newunstable: raise error.Abort(_("cannot %s changeset with children") % action) def disallowednewunstable(repo, revs): """Checks whether editing the revs will create new unstable changesets and are we allowed to create them. To allow new unstable changesets, set the config: `experimental.evolution.allowunstable=True` """ allowunstable = obsolete.isenabled(repo, obsolete.allowunstableopt) if allowunstable: return revset.baseset() return repo.revs("(%ld::) - %ld", revs, revs)