Mercurial > hg
view hgext/strip.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 | f442c9494ec7 |
children | c303d65d2e34 |
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"""strip changesets and their descendants from history This extension allows you to strip changesets and all their descendants from the repository. See the command help for details. """ from __future__ import absolute_import from mercurial.i18n import _ from mercurial import ( bookmarks as bookmarksmod, cmdutil, error, hg, lock as lockmod, merge, node as nodemod, pycompat, registrar, repair, scmutil, util, ) nullid = nodemod.nullid release = lockmod.release 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' def checksubstate(repo, baserev=None): '''return list of subrepos at a different revision than substate. Abort if any subrepos have uncommitted changes.''' inclsubs = [] wctx = repo[None] if baserev: bctx = repo[baserev] else: bctx = wctx.parents()[0] for s in sorted(wctx.substate): wctx.sub(s).bailifchanged(True) if s not in bctx.substate or bctx.sub(s).dirty(): inclsubs.append(s) return inclsubs def checklocalchanges(repo, force=False, excsuffix=''): cmdutil.checkunfinished(repo) s = repo.status() if not force: if s.modified or s.added or s.removed or s.deleted: _("local changes found") # i18n tool detection raise error.Abort(_("local changes found" + excsuffix)) if checksubstate(repo): _("local changed subrepos found") # i18n tool detection raise error.Abort(_("local changed subrepos found" + excsuffix)) return s def _findupdatetarget(repo, nodes): unode, p2 = repo.changelog.parents(nodes[0]) currentbranch = repo[None].branch() if (util.safehasattr(repo, 'mq') and p2 != nullid and p2 in [x.node for x in repo.mq.applied]): unode = p2 elif currentbranch != repo[unode].branch(): pwdir = 'parents(wdir())' revset = 'max(((parents(%ln::%r) + %r) - %ln::%r) and branch(%s))' branchtarget = repo.revs(revset, nodes, pwdir, pwdir, nodes, pwdir, currentbranch) if branchtarget: cl = repo.changelog unode = cl.node(branchtarget.first()) return unode def strip(ui, repo, revs, update=True, backup=True, force=None, bookmarks=None): with repo.wlock(), repo.lock(): if update: checklocalchanges(repo, force=force) urev = _findupdatetarget(repo, revs) hg.clean(repo, urev) repo.dirstate.write(repo.currenttransaction()) repair.strip(ui, repo, revs, backup) repomarks = repo._bookmarks if bookmarks: with repo.transaction('strip') as tr: if repo._activebookmark in bookmarks: bookmarksmod.deactivate(repo) repomarks.applychanges(repo, tr, [(b, None) for b in bookmarks]) for bookmark in sorted(bookmarks): ui.write(_("bookmark '%s' deleted\n") % bookmark) @command("strip", [ ('r', 'rev', [], _('strip specified revision (optional, ' 'can specify revisions without this ' 'option)'), _('REV')), ('f', 'force', None, _('force removal of changesets, discard ' 'uncommitted changes (no backup)')), ('', 'no-backup', None, _('do not save backup bundle')), ('', 'nobackup', None, _('do not save backup bundle ' '(DEPRECATED)')), ('n', '', None, _('ignored (DEPRECATED)')), ('k', 'keep', None, _("do not modify working directory during " "strip")), ('B', 'bookmark', [], _("remove revs only reachable from given" " bookmark"))], _('hg strip [-k] [-f] [-B bookmark] [-r] REV...')) def stripcmd(ui, repo, *revs, **opts): """strip changesets and all their descendants from the repository The strip command removes the specified changesets and all their descendants. If the working directory has uncommitted changes, the operation is aborted unless the --force flag is supplied, in which case changes will be discarded. If a parent of the working directory is stripped, then the working directory will automatically be updated to the most recent available ancestor of the stripped parent after the operation completes. Any stripped changesets are stored in ``.hg/strip-backup`` as a bundle (see :hg:`help bundle` and :hg:`help unbundle`). They can be restored by running :hg:`unbundle .hg/strip-backup/BUNDLE`, where BUNDLE is the bundle file created by the strip. Note that the local revision numbers will in general be different after the restore. Use the --no-backup option to discard the backup bundle once the operation completes. Strip is not a history-rewriting operation and can be used on changesets in the public phase. But if the stripped changesets have been pushed to a remote repository you will likely pull them again. Return 0 on success. """ opts = pycompat.byteskwargs(opts) backup = True if opts.get('no_backup') or opts.get('nobackup'): backup = False cl = repo.changelog revs = list(revs) + opts.get('rev') revs = set(scmutil.revrange(repo, revs)) with repo.wlock(): bookmarks = set(opts.get('bookmark')) if bookmarks: repomarks = repo._bookmarks if not bookmarks.issubset(repomarks): raise error.Abort(_("bookmark '%s' not found") % ','.join(sorted(bookmarks - set(repomarks.keys())))) # If the requested bookmark is not the only one pointing to a # a revision we have to only delete the bookmark and not strip # anything. revsets cannot detect that case. nodetobookmarks = {} for mark, node in repomarks.iteritems(): nodetobookmarks.setdefault(node, []).append(mark) for marks in nodetobookmarks.values(): if bookmarks.issuperset(marks): rsrevs = scmutil.bookmarkrevs(repo, marks[0]) revs.update(set(rsrevs)) if not revs: with repo.lock(), repo.transaction('bookmark') as tr: bmchanges = [(b, None) for b in bookmarks] repomarks.applychanges(repo, tr, bmchanges) for bookmark in sorted(bookmarks): ui.write(_("bookmark '%s' deleted\n") % bookmark) if not revs: raise error.Abort(_('empty revision set')) descendants = set(cl.descendants(revs)) strippedrevs = revs.union(descendants) roots = revs.difference(descendants) # if one of the wdir parent is stripped we'll need # to update away to an earlier revision update = any(p != nullid and cl.rev(p) in strippedrevs for p in repo.dirstate.parents()) rootnodes = set(cl.node(r) for r in roots) q = getattr(repo, 'mq', None) if q is not None and q.applied: # refresh queue state if we're about to strip # applied patches if cl.rev(repo.lookup('qtip')) in strippedrevs: q.applieddirty = True start = 0 end = len(q.applied) for i, statusentry in enumerate(q.applied): if statusentry.node in rootnodes: # if one of the stripped roots is an applied # patch, only part of the queue is stripped start = i break del q.applied[start:end] q.savedirty() revs = sorted(rootnodes) if update and opts.get('keep'): urev = _findupdatetarget(repo, revs) uctx = repo[urev] # only reset the dirstate for files that would actually change # between the working context and uctx descendantrevs = repo.revs(b"%d::.", uctx.rev()) changedfiles = [] for rev in descendantrevs: # blindly reset the files, regardless of what actually changed changedfiles.extend(repo[rev].files()) # reset files that only changed in the dirstate too dirstate = repo.dirstate dirchanges = [f for f in dirstate if dirstate[f] != 'n'] changedfiles.extend(dirchanges) repo.dirstate.rebuild(urev, uctx.manifest(), changedfiles) repo.dirstate.write(repo.currenttransaction()) # clear resolve state merge.mergestate.clean(repo, repo['.'].node()) update = False strip(ui, repo, revs, backup=backup, update=update, force=opts.get('force'), bookmarks=bookmarks) return 0