view mercurial/branchmap.py @ 23225:bdf7b1ea1dae stable

changegroup: don't store unused value on fnodes (issue4443)

The contents of fnodes are only accessed once per key. It is wasteful to
cache the value since nobody will use it.

Before this patch, the caching of unused data in fnodes was effectively
causing a memory leak during the file streaming part of bundle creation.

On mozilla-central (which has ~190,000 entries in fnodes), this patch
has a significant impact on RSS at the end of generate():

before:  516,124 KB
after:   364,356 KB
delta:  -151,768 KB

The origin of this code can be traced back to 627cd7842e5d and has been
with us since the 2.7 release.

# branchmap.py - logic to computes, maintain and stores branchmap for local repo
#
# Copyright 2005-2007 Matt Mackall <[e-mail]>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.

from node import bin, hex, nullid, nullrev
import encoding
import util
import time

def _filename(repo):
    """name of a branchcache file for a given repo or repoview"""
    filename = "cache/branch2"
    if repo.filtername:
        filename = '%s-%s' % (filename, repo.filtername)
    return filename

def read(repo):
    try:
        f = repo.opener(_filename(repo))
        lines = f.read().split('\n')
        f.close()
    except (IOError, OSError):
        return None

    try:
        cachekey = lines.pop(0).split(" ", 2)
        last, lrev = cachekey[:2]
        last, lrev = bin(last), int(lrev)
        filteredhash = None
        if len(cachekey) > 2:
            filteredhash = bin(cachekey[2])
        partial = branchcache(tipnode=last, tiprev=lrev,
                              filteredhash=filteredhash)
        if not partial.validfor(repo):
            # invalidate the cache
            raise ValueError('tip differs')
        for l in lines:
            if not l:
                continue
            node, state, label = l.split(" ", 2)
            if state not in 'oc':
                raise ValueError('invalid branch state')
            label = encoding.tolocal(label.strip())
            if not node in repo:
                raise ValueError('node %s does not exist' % node)
            node = bin(node)
            partial.setdefault(label, []).append(node)
            if state == 'c':
                partial._closednodes.add(node)
    except KeyboardInterrupt:
        raise
    except Exception, inst:
        if repo.ui.debugflag:
            msg = 'invalid branchheads cache'
            if repo.filtername is not None:
                msg += ' (%s)' % repo.filtername
            msg += ': %s\n'
            repo.ui.debug(msg % inst)
        partial = None
    return partial

### Nearest subset relation
# Nearest subset of filter X is a filter Y so that:
# * Y is included in X,
# * X - Y is as small as possible.
# This create and ordering used for branchmap purpose.
# the ordering may be partial
subsettable = {None: 'visible',
               'visible': 'served',
               'served': 'immutable',
               'immutable': 'base'}

def updatecache(repo):
    cl = repo.changelog
    filtername = repo.filtername
    partial = repo._branchcaches.get(filtername)

    revs = []
    if partial is None or not partial.validfor(repo):
        partial = read(repo)
        if partial is None:
            subsetname = subsettable.get(filtername)
            if subsetname is None:
                partial = branchcache()
            else:
                subset = repo.filtered(subsetname)
                partial = subset.branchmap().copy()
                extrarevs = subset.changelog.filteredrevs - cl.filteredrevs
                revs.extend(r for  r in extrarevs if r <= partial.tiprev)
    revs.extend(cl.revs(start=partial.tiprev + 1))
    if revs:
        partial.update(repo, revs)
        partial.write(repo)
    assert partial.validfor(repo), filtername
    repo._branchcaches[repo.filtername] = partial

class branchcache(dict):
    """A dict like object that hold branches heads cache.

    This cache is used to avoid costly computations to determine all the
    branch heads of a repo.

    The cache is serialized on disk in the following format:

    <tip hex node> <tip rev number> [optional filtered repo hex hash]
    <branch head hex node> <open/closed state> <branch name>
    <branch head hex node> <open/closed state> <branch name>
    ...

    The first line is used to check if the cache is still valid. If the
    branch cache is for a filtered repo view, an optional third hash is
    included that hashes the hashes of all filtered revisions.

    The open/closed state is represented by a single letter 'o' or 'c'.
    This field can be used to avoid changelog reads when determining if a
    branch head closes a branch or not.
    """

    def __init__(self, entries=(), tipnode=nullid, tiprev=nullrev,
                 filteredhash=None, closednodes=None):
        super(branchcache, self).__init__(entries)
        self.tipnode = tipnode
        self.tiprev = tiprev
        self.filteredhash = filteredhash
        # closednodes is a set of nodes that close their branch. If the branch
        # cache has been updated, it may contain nodes that are no longer
        # heads.
        if closednodes is None:
            self._closednodes = set()
        else:
            self._closednodes = closednodes

    def _hashfiltered(self, repo):
        """build hash of revision filtered in the current cache

        Tracking tipnode and tiprev is not enough to ensure validity of the
        cache as they do not help to distinct cache that ignored various
        revision bellow tiprev.

        To detect such difference, we build a cache of all ignored revisions.
        """
        cl = repo.changelog
        if not cl.filteredrevs:
            return None
        key = None
        revs = sorted(r for r in cl.filteredrevs if r <= self.tiprev)
        if revs:
            s = util.sha1()
            for rev in revs:
                s.update('%s;' % rev)
            key = s.digest()
        return key

    def validfor(self, repo):
        """Is the cache content valid regarding a repo

        - False when cached tipnode is unknown or if we detect a strip.
        - True when cache is up to date or a subset of current repo."""
        try:
            return ((self.tipnode == repo.changelog.node(self.tiprev))
                    and (self.filteredhash == self._hashfiltered(repo)))
        except IndexError:
            return False

    def _branchtip(self, heads):
        '''Return tuple with last open head in heads and false,
        otherwise return last closed head and true.'''
        tip = heads[-1]
        closed = True
        for h in reversed(heads):
            if h not in self._closednodes:
                tip = h
                closed = False
                break
        return tip, closed

    def branchtip(self, branch):
        '''Return the tipmost open head on branch head, otherwise return the
        tipmost closed head on branch.
        Raise KeyError for unknown branch.'''
        return self._branchtip(self[branch])[0]

    def branchheads(self, branch, closed=False):
        heads = self[branch]
        if not closed:
            heads = [h for h in heads if h not in self._closednodes]
        return heads

    def iterbranches(self):
        for bn, heads in self.iteritems():
            yield (bn, heads) + self._branchtip(heads)

    def copy(self):
        """return an deep copy of the branchcache object"""
        return branchcache(self, self.tipnode, self.tiprev, self.filteredhash,
                           self._closednodes)

    def write(self, repo):
        try:
            f = repo.opener(_filename(repo), "w", atomictemp=True)
            cachekey = [hex(self.tipnode), str(self.tiprev)]
            if self.filteredhash is not None:
                cachekey.append(hex(self.filteredhash))
            f.write(" ".join(cachekey) + '\n')
            nodecount = 0
            for label, nodes in sorted(self.iteritems()):
                for node in nodes:
                    nodecount += 1
                    if node in self._closednodes:
                        state = 'c'
                    else:
                        state = 'o'
                    f.write("%s %s %s\n" % (hex(node), state,
                                            encoding.fromlocal(label)))
            f.close()
            repo.ui.log('branchcache',
                        'wrote %s branch cache with %d labels and %d nodes\n',
                        repo.filtername, len(self), nodecount)
        except (IOError, OSError, util.Abort), inst:
            repo.ui.debug("couldn't write branch cache: %s\n" % inst)
            # Abort may be raise by read only opener
            pass

    def update(self, repo, revgen):
        """Given a branchhead cache, self, that may have extra nodes or be
        missing heads, and a generator of nodes that are strictly a superset of
        heads missing, this function updates self to be correct.
        """
        starttime = time.time()
        cl = repo.changelog
        # collect new branch entries
        newbranches = {}
        getbranchinfo = cl.branchinfo
        for r in revgen:
            branch, closesbranch = getbranchinfo(r)
            newbranches.setdefault(branch, []).append(r)
            if closesbranch:
                self._closednodes.add(cl.node(r))

        # fetch current topological heads to speed up filtering
        topoheads = set(cl.headrevs())

        # if older branchheads are reachable from new ones, they aren't
        # really branchheads. Note checking parents is insufficient:
        # 1 (branch a) -> 2 (branch b) -> 3 (branch a)
        for branch, newheadrevs in newbranches.iteritems():
            bheads = self.setdefault(branch, [])
            bheadset = set(cl.rev(node) for node in bheads)

            # This have been tested True on all internal usage of this function.
            # run it again in case of doubt
            # assert not (set(bheadrevs) & set(newheadrevs))
            newheadrevs.sort()
            bheadset.update(newheadrevs)

            # This prunes out two kinds of heads - heads that are superseded by
            # a head in newheadrevs, and newheadrevs that are not heads because
            # an existing head is their descendant.
            uncertain = bheadset - topoheads
            if uncertain:
                floorrev = min(uncertain)
                ancestors = set(cl.ancestors(newheadrevs, floorrev))
                bheadset -= ancestors
            bheadrevs = sorted(bheadset)
            self[branch] = [cl.node(rev) for rev in bheadrevs]
            tiprev = bheadrevs[-1]
            if tiprev > self.tiprev:
                self.tipnode = cl.node(tiprev)
                self.tiprev = tiprev

        if not self.validfor(repo):
            # cache key are not valid anymore
            self.tipnode = nullid
            self.tiprev = nullrev
            for heads in self.values():
                tiprev = max(cl.rev(node) for node in heads)
                if tiprev > self.tiprev:
                    self.tipnode = cl.node(tiprev)
                    self.tiprev = tiprev
        self.filteredhash = self._hashfiltered(repo)

        duration = time.time() - starttime
        repo.ui.log('branchcache', 'updated %s branch cache in %.4f seconds\n',
                    repo.filtername, duration)