Mercurial > hg
view mercurial/repair.py @ 35793:4fb2bb61597c
bundle2: increase payload part chunk size to 32kb
Bundle2 payload parts are framed chunks. Esentially, we obtain
data in equal size chunks of size `preferedchunksize` and emit those
to a generator. That generator is fed into a compressor (which can
be the no-op compressor, which just re-emits the generator). And
the output from the compressor likely goes to a file descriptor
or socket.
What this means is that small chunk sizes create more Python objects
and Python function calls than larger chunk sizes. And as we know,
Python object and function call overhead in performance sensitive
code matters (at least with CPython).
This commit increases the bundle2 part payload chunk size from 4k
to 32k. Practically speaking, this means that the chunks we feed
into a compressor (implemented in C code) or feed directly into a
file handle or socket write() are larger. It's possible the chunks
might be larger than what the receiver can handle in one logical
operation. But at that point, we're in C code, which is much more
efficient at dealing with splitting up the chunk and making multiple
function calls than Python is.
A downside to larger chunks is that the receiver has to wait for that
much data to arrive (either raw or from a decompressor) before it
can process the chunk. But 32kb still feels like a small buffer to
have to wait for. And in many cases, the client will convert from
8 read(4096) to 1 read(32768). That's happening in Python land. So
we cut down on the number of Python objects and function calls,
making the client faster as well. I don't think there are any
significant concerns to increasing the payload chunk size to 32kb.
The impact of this change on performance significant. Using `curl`
to obtain a stream clone bundle2 payload from a server on localhost
serving the mozilla-unified repository:
before: 20.78 user; 7.71 system; 80.5 MB/s
after: 13.90 user; 3.51 system; 132 MB/s
legacy: 9.72 user; 8.16 system; 132 MB/s
bundle2 stream clone generation is still more resource intensive than
legacy stream clone (that's likely because of the use of a
util.chunkbuffer). But the throughput is the same. We might
be in territory we're this is effectively a benchmark of the
networking stack or Python's syscall throughput.
From the client perspective, `hg clone -U --stream`:
before: 33.50 user; 7.95 system; 53.3 MB/s
after: 22.82 user; 7.33 system; 72.7 MB/s
legacy: 29.96 user; 7.94 system; 58.0 MB/s
And for `hg clone --stream` with a working directory update of
~230k files:
after: 119.55 user; 26.47 system; 0:57.08 wall
legacy: 126.98 user; 26.94 system; 1:05.56 wall
So, it appears that bundle2's stream clone is now definitively faster
than legacy stream clone!
Differential Revision: https://phab.mercurial-scm.org/D1932
author | Gregory Szorc <gregory.szorc@gmail.com> |
---|---|
date | Sat, 20 Jan 2018 22:55:42 -0800 |
parents | 128dd940bedc |
children | f659a407e5ee |
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# repair.py - functions for repository repair for mercurial # # Copyright 2005, 2006 Chris Mason <mason@suse.com> # Copyright 2007 Matt Mackall # # 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 import errno import hashlib from .i18n import _ from .node import ( hex, short, ) from . import ( bundle2, changegroup, discovery, error, exchange, obsolete, obsutil, util, ) def _bundle(repo, bases, heads, node, suffix, compress=True, obsolescence=True): """create a bundle with the specified revisions as a backup""" backupdir = "strip-backup" vfs = repo.vfs if not vfs.isdir(backupdir): vfs.mkdir(backupdir) # Include a hash of all the nodes in the filename for uniqueness allcommits = repo.set('%ln::%ln', bases, heads) allhashes = sorted(c.hex() for c in allcommits) totalhash = hashlib.sha1(''.join(allhashes)).digest() name = "%s/%s-%s-%s.hg" % (backupdir, short(node), hex(totalhash[:4]), suffix) cgversion = changegroup.localversion(repo) comp = None if cgversion != '01': bundletype = "HG20" if compress: comp = 'BZ' elif compress: bundletype = "HG10BZ" else: bundletype = "HG10UN" outgoing = discovery.outgoing(repo, missingroots=bases, missingheads=heads) contentopts = { 'cg.version': cgversion, 'obsolescence': obsolescence, 'phases': True, } return bundle2.writenewbundle(repo.ui, repo, 'strip', name, bundletype, outgoing, contentopts, vfs, compression=comp) def _collectfiles(repo, striprev): """find out the filelogs affected by the strip""" files = set() for x in xrange(striprev, len(repo)): files.update(repo[x].files()) return sorted(files) def _collectrevlog(revlog, striprev): _, brokenset = revlog.getstrippoint(striprev) return [revlog.linkrev(r) for r in brokenset] def _collectmanifest(repo, striprev): return _collectrevlog(repo.manifestlog._revlog, striprev) def _collectbrokencsets(repo, files, striprev): """return the changesets which will be broken by the truncation""" s = set() s.update(_collectmanifest(repo, striprev)) for fname in files: s.update(_collectrevlog(repo.file(fname), striprev)) return s def strip(ui, repo, nodelist, backup=True, topic='backup'): # This function requires the caller to lock the repo, but it operates # within a transaction of its own, and thus requires there to be no current # transaction when it is called. if repo.currenttransaction() is not None: raise error.ProgrammingError('cannot strip from inside a transaction') # Simple way to maintain backwards compatibility for this # argument. if backup in ['none', 'strip']: backup = False repo = repo.unfiltered() repo.destroying() cl = repo.changelog # TODO handle undo of merge sets if isinstance(nodelist, str): nodelist = [nodelist] striplist = [cl.rev(node) for node in nodelist] striprev = min(striplist) files = _collectfiles(repo, striprev) saverevs = _collectbrokencsets(repo, files, striprev) # Some revisions with rev > striprev may not be descendants of striprev. # We have to find these revisions and put them in a bundle, so that # we can restore them after the truncations. # To create the bundle we use repo.changegroupsubset which requires # the list of heads and bases of the set of interesting revisions. # (head = revision in the set that has no descendant in the set; # base = revision in the set that has no ancestor in the set) tostrip = set(striplist) saveheads = set(saverevs) for r in cl.revs(start=striprev + 1): if any(p in tostrip for p in cl.parentrevs(r)): tostrip.add(r) if r not in tostrip: saverevs.add(r) saveheads.difference_update(cl.parentrevs(r)) saveheads.add(r) saveheads = [cl.node(r) for r in saveheads] # compute base nodes if saverevs: descendants = set(cl.descendants(saverevs)) saverevs.difference_update(descendants) savebases = [cl.node(r) for r in saverevs] stripbases = [cl.node(r) for r in tostrip] stripobsidx = obsmarkers = () if repo.ui.configbool('devel', 'strip-obsmarkers'): obsmarkers = obsutil.exclusivemarkers(repo, stripbases) if obsmarkers: stripobsidx = [i for i, m in enumerate(repo.obsstore) if m in obsmarkers] # For a set s, max(parents(s) - s) is the same as max(heads(::s - s)), but # is much faster newbmtarget = repo.revs('max(parents(%ld) - (%ld))', tostrip, tostrip) if newbmtarget: newbmtarget = repo[newbmtarget.first()].node() else: newbmtarget = '.' bm = repo._bookmarks updatebm = [] for m in bm: rev = repo[bm[m]].rev() if rev in tostrip: updatebm.append(m) # create a changegroup for all the branches we need to keep backupfile = None vfs = repo.vfs node = nodelist[-1] if backup: backupfile = _bundle(repo, stripbases, cl.heads(), node, topic) repo.ui.status(_("saved backup bundle to %s\n") % vfs.join(backupfile)) repo.ui.log("backupbundle", "saved backup bundle to %s\n", vfs.join(backupfile)) tmpbundlefile = None if saveheads: # do not compress temporary bundle if we remove it from disk later # # We do not include obsolescence, it might re-introduce prune markers # we are trying to strip. This is harmless since the stripped markers # are already backed up and we did not touched the markers for the # saved changesets. tmpbundlefile = _bundle(repo, savebases, saveheads, node, 'temp', compress=False, obsolescence=False) try: with repo.transaction("strip") as tr: offset = len(tr.entries) tr.startgroup() cl.strip(striprev, tr) stripmanifest(repo, striprev, tr, files) for fn in files: repo.file(fn).strip(striprev, tr) tr.endgroup() for i in xrange(offset, len(tr.entries)): file, troffset, ignore = tr.entries[i] with repo.svfs(file, 'a', checkambig=True) as fp: fp.truncate(troffset) if troffset == 0: repo.store.markremoved(file) deleteobsmarkers(repo.obsstore, stripobsidx) del repo.obsstore repo.invalidatevolatilesets() repo._phasecache.filterunknown(repo) if tmpbundlefile: ui.note(_("adding branch\n")) f = vfs.open(tmpbundlefile, "rb") gen = exchange.readbundle(ui, f, tmpbundlefile, vfs) if not repo.ui.verbose: # silence internal shuffling chatter repo.ui.pushbuffer() tmpbundleurl = 'bundle:' + vfs.join(tmpbundlefile) txnname = 'strip' if not isinstance(gen, bundle2.unbundle20): txnname = "strip\n%s" % util.hidepassword(tmpbundleurl) with repo.transaction(txnname) as tr: bundle2.applybundle(repo, gen, tr, source='strip', url=tmpbundleurl) if not repo.ui.verbose: repo.ui.popbuffer() f.close() with repo.transaction('repair') as tr: bmchanges = [(m, repo[newbmtarget].node()) for m in updatebm] bm.applychanges(repo, tr, bmchanges) # remove undo files for undovfs, undofile in repo.undofiles(): try: undovfs.unlink(undofile) except OSError as e: if e.errno != errno.ENOENT: ui.warn(_('error removing %s: %s\n') % (undovfs.join(undofile), str(e))) except: # re-raises if backupfile: ui.warn(_("strip failed, backup bundle stored in '%s'\n") % vfs.join(backupfile)) if tmpbundlefile: ui.warn(_("strip failed, unrecovered changes stored in '%s'\n") % vfs.join(tmpbundlefile)) ui.warn(_("(fix the problem, then recover the changesets with " "\"hg unbundle '%s'\")\n") % vfs.join(tmpbundlefile)) raise else: if tmpbundlefile: # Remove temporary bundle only if there were no exceptions vfs.unlink(tmpbundlefile) repo.destroyed() # return the backup file path (or None if 'backup' was False) so # extensions can use it return backupfile def safestriproots(ui, repo, nodes): """return list of roots of nodes where descendants are covered by nodes""" torev = repo.unfiltered().changelog.rev revs = set(torev(n) for n in nodes) # tostrip = wanted - unsafe = wanted - ancestors(orphaned) # orphaned = affected - wanted # affected = descendants(roots(wanted)) # wanted = revs tostrip = set(repo.revs('%ld-(::((roots(%ld)::)-%ld))', revs, revs, revs)) notstrip = revs - tostrip if notstrip: nodestr = ', '.join(sorted(short(repo[n].node()) for n in notstrip)) ui.warn(_('warning: orphaned descendants detected, ' 'not stripping %s\n') % nodestr) return [c.node() for c in repo.set('roots(%ld)', tostrip)] class stripcallback(object): """used as a transaction postclose callback""" def __init__(self, ui, repo, backup, topic): self.ui = ui self.repo = repo self.backup = backup self.topic = topic or 'backup' self.nodelist = [] def addnodes(self, nodes): self.nodelist.extend(nodes) def __call__(self, tr): roots = safestriproots(self.ui, self.repo, self.nodelist) if roots: strip(self.ui, self.repo, roots, self.backup, self.topic) def delayedstrip(ui, repo, nodelist, topic=None): """like strip, but works inside transaction and won't strip irreverent revs nodelist must explicitly contain all descendants. Otherwise a warning will be printed that some nodes are not stripped. Always do a backup. The last non-None "topic" will be used as the backup topic name. The default backup topic name is "backup". """ tr = repo.currenttransaction() if not tr: nodes = safestriproots(ui, repo, nodelist) return strip(ui, repo, nodes, True, topic) # transaction postclose callbacks are called in alphabet order. # use '\xff' as prefix so we are likely to be called last. callback = tr.getpostclose('\xffstrip') if callback is None: callback = stripcallback(ui, repo, True, topic) tr.addpostclose('\xffstrip', callback) if topic: callback.topic = topic callback.addnodes(nodelist) def stripmanifest(repo, striprev, tr, files): revlog = repo.manifestlog._revlog revlog.strip(striprev, tr) striptrees(repo, tr, striprev, files) def striptrees(repo, tr, striprev, files): if 'treemanifest' in repo.requirements: # safe but unnecessary # otherwise for unencoded, encoded, size in repo.store.datafiles(): if (unencoded.startswith('meta/') and unencoded.endswith('00manifest.i')): dir = unencoded[5:-12] repo.manifestlog._revlog.dirlog(dir).strip(striprev, tr) def rebuildfncache(ui, repo): """Rebuilds the fncache file from repo history. Missing entries will be added. Extra entries will be removed. """ repo = repo.unfiltered() if 'fncache' not in repo.requirements: ui.warn(_('(not rebuilding fncache because repository does not ' 'support fncache)\n')) return with repo.lock(): fnc = repo.store.fncache # Trigger load of fncache. if 'irrelevant' in fnc: pass oldentries = set(fnc.entries) newentries = set() seenfiles = set() repolen = len(repo) for rev in repo: ui.progress(_('rebuilding'), rev, total=repolen, unit=_('changesets')) ctx = repo[rev] for f in ctx.files(): # This is to minimize I/O. if f in seenfiles: continue seenfiles.add(f) i = 'data/%s.i' % f d = 'data/%s.d' % f if repo.store._exists(i): newentries.add(i) if repo.store._exists(d): newentries.add(d) ui.progress(_('rebuilding'), None) if 'treemanifest' in repo.requirements: # safe but unnecessary otherwise for dir in util.dirs(seenfiles): i = 'meta/%s/00manifest.i' % dir d = 'meta/%s/00manifest.d' % dir if repo.store._exists(i): newentries.add(i) if repo.store._exists(d): newentries.add(d) addcount = len(newentries - oldentries) removecount = len(oldentries - newentries) for p in sorted(oldentries - newentries): ui.write(_('removing %s\n') % p) for p in sorted(newentries - oldentries): ui.write(_('adding %s\n') % p) if addcount or removecount: ui.write(_('%d items added, %d removed from fncache\n') % (addcount, removecount)) fnc.entries = newentries fnc._dirty = True with repo.transaction('fncache') as tr: fnc.write(tr) else: ui.write(_('fncache already up to date\n')) def stripbmrevset(repo, mark): """ The revset to strip when strip is called with -B mark Needs to live here so extensions can use it and wrap it even when strip is not enabled or not present on a box. """ return repo.revs("ancestors(bookmark(%s)) - " "ancestors(head() and not bookmark(%s)) - " "ancestors(bookmark() and not bookmark(%s))", mark, mark, mark) def deleteobsmarkers(obsstore, indices): """Delete some obsmarkers from obsstore and return how many were deleted 'indices' is a list of ints which are the indices of the markers to be deleted. Every invocation of this function completely rewrites the obsstore file, skipping the markers we want to be removed. The new temporary file is created, remaining markers are written there and on .close() this file gets atomically renamed to obsstore, thus guaranteeing consistency.""" if not indices: # we don't want to rewrite the obsstore with the same content return left = [] current = obsstore._all n = 0 for i, m in enumerate(current): if i in indices: n += 1 continue left.append(m) newobsstorefile = obsstore.svfs('obsstore', 'w', atomictemp=True) for bytes in obsolete.encodemarkers(left, True, obsstore._version): newobsstorefile.write(bytes) newobsstorefile.close() return n