Mercurial > public > mercurial-scm > hg
diff mercurial/revlog.py @ 23255:76effa770ff9
revlog: add config variable for limiting delta-chain length
The current heuristic for deciding between storing delta and full texts
is based on ratio of (sizeofdeltas)/(sizeoffulltext).
In some cases (for example a manifest for ahuge repo) this approach
can result in extremely long delta chains (~30,000) which are very slow to
read. (In the case of a manifest ~500ms are added to every hg command because of that).
This commit introduces "revlog.maxchainlength" configuration variable that will
limit delta chain length.
| author | Mateusz Kwapich <mitrandir@fb.com> |
|---|---|
| date | Thu, 06 Nov 2014 14:20:05 -0800 |
| parents | d23834b871ac |
| children | 8d47c212b0dd |
line wrap: on
line diff
--- a/mercurial/revlog.py Thu Nov 06 14:08:25 2014 -0800 +++ b/mercurial/revlog.py Thu Nov 06 14:20:05 2014 -0800 @@ -204,6 +204,7 @@ self._basecache = None self._chunkcache = (0, '') self._chunkcachesize = 65536 + self._maxchainlen = None self.index = [] self._pcache = {} self._nodecache = {nullid: nullrev} @@ -219,6 +220,8 @@ v = 0 if 'chunkcachesize' in opts: self._chunkcachesize = opts['chunkcachesize'] + if 'maxchainlen' in opts: + self._maxchainlen = opts['maxchainlen'] if self._chunkcachesize <= 0: raise RevlogError(_('revlog chunk cache size %r is not greater ' @@ -1216,11 +1219,13 @@ base = rev else: base = chainbase - return dist, l, data, base, chainbase + chainlen = self.chainlen(rev) + 1 + return dist, l, data, base, chainbase, chainlen curr = len(self) prev = curr - 1 base = chainbase = curr + chainlen = None offset = self.end(prev) flags = 0 d = None @@ -1240,7 +1245,7 @@ d = builddelta(prev) else: d = builddelta(prev) - dist, l, data, base, chainbase = d + dist, l, data, base, chainbase, chainlen = d # full versions are inserted when the needed deltas # become comparable to the uncompressed text @@ -1249,7 +1254,8 @@ cachedelta[1]) else: textlen = len(text) - if d is None or dist > textlen * 2: + if (d is None or dist > textlen * 2 or + self._maxchainlen and chainlen > self._maxchainlen): text = buildtext() data = self.compress(text) l = len(data[1]) + len(data[0])