view mercurial/repair.py @ 26379:39d643252b9f

revlog: use existing file handle when reading during _addrevision

_addrevision() may need to read from revlogs as part of computing
deltas. Previously, we would flush existing file handles and open
a new, short-lived file handle to perform the reading.

If we have an existing file handle, it seems logical to reuse it
for reading instead of opening a new file handle. This patch
makes that the new behavior.

After this patch, revlog files are only reopened when adding
revisions if the revlog is switched from inline to non-inline.

On Linux when unbundling a bundle of the mozilla-central repo, this
patch has the following impact on system call counts:

Call     Before     After       Delta
write    827,639    673,390   -154,249
open     700,103    684,089    -16,014
read      74,489     74,489          0
fstat    493,924    461,896    -32,028
close    249,131    233,117    -16,014
stat     242,001    242,001          0
lstat     18,676     18,676          0
lseek     20,268     20,268          0
ioctl     14,652     13,173     -1,479
TOTAL  3,180,758  2,930,679   -250,079

It's worth noting that many of the open() calls fail due to missing
files. That's why there are many more open() calls than close().

Despite the significant system call reduction, this change does not
seem to have a significant performance impact on Linux.

On Windows 10 (not a VM, on a SSD), this patch appears to reduce
unbundle time for mozilla-central from ~960s to ~920s. This isn't
as significant as I was hoping. But a decrease it is nonetheless.
Still, Windows unbundle performance is still >2x slower than Linux.

Despite the lack of significant gains, fewer system calls is fewer
system calls. If nothing else, this will narrow the focus of potential
areas to optimize in the future.

# repair.py - functions for repository repair for mercurial
#
# Copyright 2005, 2006 Chris Mason <[e-mail]>
# 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

from .i18n import _
from .node import short
from . import (
    bundle2,
    changegroup,
    exchange,
    util,
)

def _bundle(repo, bases, heads, node, suffix, compress=True):
    """create a bundle with the specified revisions as a backup"""
    usebundle2 = (repo.ui.configbool('experimental', 'bundle2-exp', True) and
                  repo.ui.config('experimental', 'strip-bundle2-version'))
    if usebundle2:
        cgversion = repo.ui.config('experimental', 'strip-bundle2-version')
        if cgversion not in changegroup.packermap:
            repo.ui.warn(_('unknown strip-bundle2-version value %r; '
                            'should be one of %r\n') %
                         (cgversion, sorted(changegroup.packermap.keys()),))
            cgversion = '01'
            usebundle2 = False
    else:
        cgversion = '01'

    cg = changegroup.changegroupsubset(repo, bases, heads, 'strip',
                                       version=cgversion)
    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 = util.sha1(''.join(allhashes)).hexdigest()
    name = "%s/%s-%s-%s.hg" % (backupdir, short(node), totalhash[:8], suffix)

    if usebundle2:
        bundletype = "HG20"
    elif compress:
        bundletype = "HG10BZ"
    else:
        bundletype = "HG10UN"
    return changegroup.writebundle(repo.ui, cg, name, bundletype, vfs)

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 _collectbrokencsets(repo, files, striprev):
    """return the changesets which will be broken by the truncation"""
    s = set()
    def collectone(revlog):
        _, brokenset = revlog.getstrippoint(striprev)
        s.update([revlog.linkrev(r) for r in brokenset])

    collectone(repo.manifest)
    for fname in files:
        collectone(repo.file(fname))

    return s

def strip(ui, repo, nodelist, backup=True, topic='backup'):

    # 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)

    # 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)
    for rev in striplist:
        for desc in cl.descendants([rev]):
            tostrip.add(desc)

    files = _collectfiles(repo, striprev)
    saverevs = _collectbrokencsets(repo, files, striprev)

    # compute heads
    saveheads = set(saverevs)
    for r in xrange(striprev + 1, len(cl)):
        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]

    # 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))
    if saveheads or savebases:
        # do not compress partial bundle if we remove it from disk later
        chgrpfile = _bundle(repo, savebases, saveheads, node, 'temp',
                            compress=False)

    mfst = repo.manifest

    curtr = repo.currenttransaction()
    if curtr is not None:
        del curtr  # avoid carrying reference to transaction for nothing
        msg = _('programming error: cannot strip from inside a transaction')
        raise util.Abort(msg, hint=_('contact your extension maintainer'))

    tr = repo.transaction("strip")
    offset = len(tr.entries)

    try:
        tr.startgroup()
        cl.strip(striprev, tr)
        mfst.strip(striprev, tr)
        for fn in files:
            repo.file(fn).strip(striprev, tr)
        tr.endgroup()

        try:
            for i in xrange(offset, len(tr.entries)):
                file, troffset, ignore = tr.entries[i]
                repo.svfs(file, 'a').truncate(troffset)
                if troffset == 0:
                    repo.store.markremoved(file)
            tr.close()
        finally:
            tr.release()

        if saveheads or savebases:
            ui.note(_("adding branch\n"))
            f = vfs.open(chgrpfile, "rb")
            gen = exchange.readbundle(ui, f, chgrpfile, vfs)
            if not repo.ui.verbose:
                # silence internal shuffling chatter
                repo.ui.pushbuffer()
            if isinstance(gen, bundle2.unbundle20):
                tr = repo.transaction('strip')
                tr.hookargs = {'source': 'strip',
                               'url': 'bundle:' + vfs.join(chgrpfile)}
                try:
                    bundle2.processbundle(repo, gen, lambda: tr)
                    tr.close()
                finally:
                    tr.release()
            else:
                changegroup.addchangegroup(repo, gen, 'strip',
                                           'bundle:' + vfs.join(chgrpfile),
                                           True)
            if not repo.ui.verbose:
                repo.ui.popbuffer()
            f.close()

        # 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)))

        for m in updatebm:
            bm[m] = repo[newbmtarget].node()
        bm.write()
    except: # re-raises
        if backupfile:
            ui.warn(_("strip failed, full bundle stored in '%s'\n")
                    % vfs.join(backupfile))
        elif saveheads:
            ui.warn(_("strip failed, partial bundle stored in '%s'\n")
                    % vfs.join(chgrpfile))
        raise
    else:
        if saveheads or savebases:
            # Remove partial backup only if there were no exceptions
            vfs.unlink(chgrpfile)

    repo.destroyed()

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

    lock = repo.lock()
    try:
        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(_('changeset'), rev, total=repolen)

            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(_('changeset'), None)

        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

            tr = repo.transaction('fncache')
            try:
                fnc.write(tr)
                tr.close()
            finally:
                tr.release()
        else:
            ui.write(_('fncache already up to date\n'))
    finally:
        lock.release()