comparison mercurial/repoview.py @ 18445:4d92e2d75cff

repoview: cache filtered changelog

Creating a new changelog object for each access is costly and prevents efficient
caching changelog side. This introduced a x5 performance regression in log
because chunk read from disk were never reused. We were jumping from about 100
disk read to about 20 000.

This changeset introduce a simple cache mechanism that help the last changelog
object created by a repoview. The changelog is reused until the changelog or the
filtering changes.

The cache invalidation is much more complicated than it should be. But MQ test
show a strange cache desync. I was unable to track down the source of this
desync in descent time so I'm not sure if the issue is in MQ or core. However
given the proximity to the 2.5 freeze, I'm choosing the inelegant but safe route
that makes the cache mechanism safer.

18444:55aff0c2b73c

    """

    def __init__(self, repo, filtername):
        object.__setattr__(self, '_unfilteredrepo', repo)
        object.__setattr__(self, 'filtername', filtername)

    # not a cacheproperty on purpose we shall implement a proper cache later
    @property
    def changelog(self):
        """return a filtered version of the changeset

        this changelog must not be used for writing"""
        # some cache may be implemented later
        cl = copy.copy(self._unfilteredrepo.changelog)
        cl.filteredrevs = filterrevs(self._unfilteredrepo, self.filtername)
        return cl

    def unfiltered(self):
        """Return an unfiltered version of a repo"""
        return self._unfilteredrepo

18445:4d92e2d75cff

    """

    def __init__(self, repo, filtername):
        object.__setattr__(self, '_unfilteredrepo', repo)
        object.__setattr__(self, 'filtername', filtername)
        object.__setattr__(self, '_clcachekey', None)
        object.__setattr__(self, '_clcache', None)

    # not a cacheproperty on purpose we shall implement a proper cache later
    @property
    def changelog(self):
        """return a filtered version of the changeset

        this changelog must not be used for writing"""
        # some cache may be implemented later
        unfi = self._unfilteredrepo
        unfichangelog = unfi.changelog
        revs = filterrevs(unfi, self.filtername)
        cl = self._clcache
        newkey = (len(unfichangelog), unfichangelog.tip(), hash(revs))
        if cl is not None:
            # we need to check curkey too for some obscure reason.
            # MQ test show a corruption of the underlying repo (in _clcache)
            # without change in the cachekey.
            oldfilter = cl.filteredrevs
            try:
                cl.filterrevs = ()  # disable filtering for tip
                curkey = (len(cl), cl.tip(), hash(oldfilter))
            finally:
                cl.filteredrevs = oldfilter
            if newkey != self._clcachekey or newkey != curkey:
                cl = None
        # could have been made None by the previous if
        if cl is None:
            cl = copy.copy(unfichangelog)
            cl.filteredrevs = revs
            object.__setattr__(self, '_clcache', cl)
            object.__setattr__(self, '_clcachekey', newkey)
        return cl

    def unfiltered(self):
        """Return an unfiltered version of a repo"""
        return self._unfilteredrepo