Mercurial > hg
view hgext/share.py @ 39506:b66ea3fc3a86
sparse-revlog: set max delta chain length to on thousand
The new snapshot system used in the sparse-revlog case gave us some small size
benefit so far. However its most important property is to gracefully handle
harder limit on delta chainlength.
Long delta chain has a very detrimental impact on read (and write) performance
in revlog. Being able to shorter them provide a great boost. However, shorting
delta used to result significantly lower compression ratio. The intermediate
snapshots effectively suppress most of this effect (even all in some case).
# Effect on the test repository
The repository we use for test is not "realistic" but can still show this in
action using an unreasonably low chain limit. Limiting the chain length show a
sizeable increase but stay under control: +6% for limit=15; +15% for limit=10.
Without the snapshot system the increase is significantly bigger: +45% for
limit=15; +80% for limit=10. Even slightly larger than without delta chain
limit, the resulting size is still smaller than before we started doing
snapshots.
Here is a table for comparison. *Since the repository is not branchy, the
initial sparse-revlog version does not bring much benefit compare to the
non-sparse one):
chain length limit | none | limit=15 | limit=10 |
without sparse-revlog | 62 818 987 | 112 664 615 | 131 222 574 |
without snapshot | 74 365 490 | 108 211 410 | 133 857 764 |
with snapshot | 59 230 936 | 63 002 924 | 68 415 329 |
# Effect On Real Life Repositories
The series provides significant benefits on all kind of repositories.
Using `hg debugupgraderepo -o redeltaparent --run`, we recomputed delta chain
for various repositories with different settings:
- delta chain length: unlimited or 1000 limit
- sparse-revlog: enabled or disabled
- this series: applied or not applied
We can observe multiple types of effect:
- On very branchy repositories:
* The delta chain limit as low impact on the repo size.
* Intermediate snapshot greatly reduces manifest size:
- pypy: -80%
- netbeans: -95%
* The delta chain limit is effective, without a size impact:
- netbeans average: 613 -> 282
- private #1 average: 1 068 -> 307
- On more linear repository:
* Intermediate snapshot limit the impact of delta chain limit:
- mozilla:
without the series: +360%
with the series: +25%
* The delta chain limit provides large improvement:
- mozilla's average chain length:
unlimited: 15 338
limited: 469
* Despite the chain length limit, the manifest size is reduced:
- mercurial: -25%
- mozilla: -30%
It is clear that the use of chains of intermediate snapshots provide large
benefits both in storage size and delta chains quality. We should now switch our
effort toward making sure the write performance are acceptable. Then,
`sparse-revlog` will be a suitable format for all new repository.
# Raw Statistic
* no-sparse: general delta repository not using sparse-revlog
* no-snapshot: sparse-revlog repository not using this series
* snapshot: sparse-revlog repository using this series
mercurial
Manifest Size:
limit | none | 1000
------------|-------------|------------
no-sparse | 8 021 373 | 8 199 366
no-snapshot | 8 103 561 | 8 259 719
snapshot | 6 137 116 | 6 126 433
Manifest Chain length data
limit || none || 1000 ||
value || average | max || average | max ||
------------||---------|---------||---------|---------||
no-sparse || 307 | 1456 || 279 | 1000 ||
no-snapshot || 312 | 1456 || 283 | 1000 ||
snapshot || 248 | 1208 || 241 | 1000 ||
Full Store Size
limit | none | 1000
------------|-------------|------------
no-sparse | 51 013 198 | 51 201 574
no-snapshot | 50 930 795 | 51 141 006
snapshot | 48 072 037 | 48 093 572
pypy
Manifest Size:
limit | none | 1000
------------|-------------|------------
no-sparse | 193 987 784 | 193 987 784
no-snapshot | 163 171 745 | 163 312 229
snapshot | 34 605 900 | 34 600 750
Manifest Chain length data
limit || none || 1000 ||
value || average | max || average | max ||
------------||---------|---------||---------|---------||
no-sparse || 101 | 692 || 101 | 692 ||
no-snapshot || 151 | 1307 || 148 | 1000 ||
snapshot || 128 | 1309 || 125 | 1000 ||
Full Store Size
limit | none | 1000
------------|-------------|------------
no-sparse | 495 931 473 | 495 931 473
no-snapshot | 465 441 017 | 465 581 501
snapshot | 355 467 301 | 355 472 451
Mozilla
Manifest Size:
limit | none | 1000
------------|----------------|---------------
no-sparse | 416 757 148 | 1 869 009 668
no-snapshot | 401 592 370 | 1 843 493 795
snapshot | 224 359 521 | 284 615 500
Manifest Chain length data
limit || none || 1000 ||
value || average | max || average | max ||
------------||---------|---------||---------|---------||
no-sparse || 15 333 | 58 980 || 468 | 1 000 ||
no-snapshot || 15 336 | 58 980 || 469 | 1 000 ||
snapshot || 15 338 | 58 983 || 469 | 1 000 ||
Full Store Size
limit | none | 1000
------------|----------------|---------------
no-sparse | 2 712 477 887 | 4 164 995 451
no-snapshot | 2 698 887 835 | 4 141 054 304
snapshot | 2 518 130 385 | 2 578 587 596
Netbeans
Manifest Size:
limit | none | 1000
------------|----------------|---------------
no-sparse | 4 766 794 101 | 4 870 642 687
no-snapshot | 4 334 806 082 | 4 428 681 309
snapshot | 232 659 666 | 240 330 665
Manifest Chain length data
limit || none || 1000 ||
value || average | max || average | max ||
------------||---------|---------||---------|---------||
no-sparse || 597 | 6802 || 254 | 1 000 ||
no-snapshot || 648 | 6 802 || 305 | 1 000 ||
snapshot || 613 | 6 804 || 282 | 1 000 ||
Full Store Size
limit | none | 1000
------------|----------------|---------------
no-sparse | 5 807 347 998 | 5 911 196 584
no-snapshot | 5 375 398 602 | 5 469 273 829
snapshot | 1 282 519 928 | 1 290 190 927
Private repo #1
Manifest Size:
limit | none | 1000
------------|-----------------|---------------
no-sparse | 41 389 010 840 | 41 398 162 091
no-snapshot | 9 737 319 435 | 10 223 773 150
snapshot | 744 215 807 | 747 961 822
Manifest Chain length data
limit || none || 1000 ||
value || average | max || average | max ||
------------||---------|---------||---------|---------||
no-sparse || 245 | 8 885 || 81 | 1 000 ||
no-snapshot || 1 225 | 8 885 || 336 | 1 000 ||
snapshot || 1 068 | 7 909 || 307 | 1 000 ||
Full Store Size
limit | none | 1000
------------|----------------|---------------
no-sparse | 49 646 065 126 | 49 655 216 377
no-snapshot | 17 924 862 856 | 18 411 316 571
snapshot | 9 009 024 710 | 9 012 770 725
Private repo #2
We currently have less data available for that repository.
* Before is a sparse-revlog repository without this series
* After is a sparse-revlog repository with this series + 1000 chain limit
Manifest Size:
Before: 1 531 485 040 bytes
After: 1 091 422 451 bytes
Manifest Chain:
Before: 2 218 avg; 6 575 Max
After: 442 avg; 1 000 Max
Full Store Size
Before: 15 203 955 615
after: 8 207 180 693
author | Boris Feld <boris.feld@octobus.net> |
---|---|
date | Fri, 07 Sep 2018 11:18:45 -0400 |
parents | 0fe7e39dc683 |
children | c303d65d2e34 |
line wrap: on
line source
# Copyright 2006, 2007 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. '''share a common history between several working directories Automatic Pooled Storage for Clones ----------------------------------- When this extension is active, :hg:`clone` can be configured to automatically share/pool storage across multiple clones. This mode effectively converts :hg:`clone` to :hg:`clone` + :hg:`share`. The benefit of using this mode is the automatic management of store paths and intelligent pooling of related repositories. The following ``share.`` config options influence this feature: ``share.pool`` Filesystem path where shared repository data will be stored. When defined, :hg:`clone` will automatically use shared repository storage instead of creating a store inside each clone. ``share.poolnaming`` How directory names in ``share.pool`` are constructed. "identity" means the name is derived from the first changeset in the repository. In this mode, different remotes share storage if their root/initial changeset is identical. In this mode, the local shared repository is an aggregate of all encountered remote repositories. "remote" means the name is derived from the source repository's path or URL. In this mode, storage is only shared if the path or URL requested in the :hg:`clone` command matches exactly to a repository that was cloned before. The default naming mode is "identity". ''' from __future__ import absolute_import import errno from mercurial.i18n import _ from mercurial import ( bookmarks, commands, error, extensions, hg, registrar, txnutil, util, ) cmdtable = {} command = registrar.command(cmdtable) # Note for extension authors: ONLY specify testedwith = 'ships-with-hg-core' for # extensions which SHIP WITH MERCURIAL. Non-mainline extensions should # be specifying the version(s) of Mercurial they are tested with, or # leave the attribute unspecified. testedwith = 'ships-with-hg-core' @command('share', [('U', 'noupdate', None, _('do not create a working directory')), ('B', 'bookmarks', None, _('also share bookmarks')), ('', 'relative', None, _('point to source using a relative path ' '(EXPERIMENTAL)')), ], _('[-U] [-B] SOURCE [DEST]'), norepo=True) def share(ui, source, dest=None, noupdate=False, bookmarks=False, relative=False): """create a new shared repository Initialize a new repository and working directory that shares its history (and optionally bookmarks) with another repository. .. note:: using rollback or extensions that destroy/modify history (mq, rebase, etc.) can cause considerable confusion with shared clones. In particular, if two shared clones are both updated to the same changeset, and one of them destroys that changeset with rollback, the other clone will suddenly stop working: all operations will fail with "abort: working directory has unknown parent". The only known workaround is to use debugsetparents on the broken clone to reset it to a changeset that still exists. """ hg.share(ui, source, dest=dest, update=not noupdate, bookmarks=bookmarks, relative=relative) return 0 @command('unshare', [], '') def unshare(ui, repo): """convert a shared repository to a normal one Copy the store data to the repo and remove the sharedpath data. """ if not repo.shared(): raise error.Abort(_("this is not a shared repo")) hg.unshare(ui, repo) # Wrap clone command to pass auto share options. def clone(orig, ui, source, *args, **opts): pool = ui.config('share', 'pool') if pool: pool = util.expandpath(pool) opts[r'shareopts'] = { 'pool': pool, 'mode': ui.config('share', 'poolnaming'), } return orig(ui, source, *args, **opts) def extsetup(ui): extensions.wrapfunction(bookmarks, '_getbkfile', getbkfile) extensions.wrapfunction(bookmarks.bmstore, '_recordchange', recordchange) extensions.wrapfunction(bookmarks.bmstore, '_writerepo', writerepo) extensions.wrapcommand(commands.table, 'clone', clone) def _hassharedbookmarks(repo): """Returns whether this repo has shared bookmarks""" try: shared = repo.vfs.read('shared').splitlines() except IOError as inst: if inst.errno != errno.ENOENT: raise return False return hg.sharedbookmarks in shared def getbkfile(orig, repo): if _hassharedbookmarks(repo): srcrepo = hg.sharedreposource(repo) if srcrepo is not None: # just orig(srcrepo) doesn't work as expected, because # HG_PENDING refers repo.root. try: fp, pending = txnutil.trypending(repo.root, repo.vfs, 'bookmarks') if pending: # only in this case, bookmark information in repo # is up-to-date. return fp fp.close() except IOError as inst: if inst.errno != errno.ENOENT: raise # otherwise, we should read bookmarks from srcrepo, # because .hg/bookmarks in srcrepo might be already # changed via another sharing repo repo = srcrepo # TODO: Pending changes in repo are still invisible in # srcrepo, because bookmarks.pending is written only into repo. # See also https://www.mercurial-scm.org/wiki/SharedRepository return orig(repo) def recordchange(orig, self, tr): # Continue with write to local bookmarks file as usual orig(self, tr) if _hassharedbookmarks(self._repo): srcrepo = hg.sharedreposource(self._repo) if srcrepo is not None: category = 'share-bookmarks' tr.addpostclose(category, lambda tr: self._writerepo(srcrepo)) def writerepo(orig, self, repo): # First write local bookmarks file in case we ever unshare orig(self, repo) if _hassharedbookmarks(self._repo): srcrepo = hg.sharedreposource(self._repo) if srcrepo is not None: orig(self, srcrepo)