Mercurial > hg
changeset 38644:43d0619cec90
revlog: enforce chunk slicing down to a certain size
Limit maximum chunk size to 4x final size when reading a revision from a
revlog. We only apply this logic when the target size is known from the
revlog.
Ideally, revlog's delta chain would be written in a way that does not trigger
this extra slicing often. However, having this second guarantee that we won't
read unexpectedly large amounts of memory in all cases is important for the
future. Future delta chain building algorithms might have good reason to
create delta chain with such characteristics.
Including this code in core as soon as possible will make Mercurial 4.7
forward-compatible with such improvement.
| author | Boris Feld <boris.feld@octobus.net> |
|---|---|
| date | Tue, 10 Jul 2018 12:20:57 +0200 |
| parents | 967fee55e8d9 |
| children | 02850baddadd |
| files | mercurial/revlog.py |
| diffstat | 1 files changed, 8 insertions(+), 3 deletions(-) [+] |
line wrap: on
line diff
--- a/mercurial/revlog.py Tue Jul 10 11:57:33 2018 +0200 +++ b/mercurial/revlog.py Tue Jul 10 12:20:57 2018 +0200 @@ -1949,7 +1949,7 @@ """ return self.decompress(self._getsegmentforrevs(rev, rev, df=df)[1]) - def _chunks(self, revs, df=None): + def _chunks(self, revs, df=None, targetsize=None): """Obtain decompressed chunks for the specified revisions. Accepts an iterable of numeric revisions that are assumed to be in @@ -1976,7 +1976,7 @@ if not self._withsparseread: slicedchunks = (revs,) else: - slicedchunks = _slicechunk(self, revs) + slicedchunks = _slicechunk(self, revs, targetsize) for revschunk in slicedchunks: firstrev = revschunk[0] @@ -2079,7 +2079,12 @@ # drop cache to save memory self._cache = None - bins = self._chunks(chain, df=_df) + targetsize = None + rawsize = self.index[rev][2] + if 0 <= rawsize: + targetsize = 4 * rawsize + + bins = self._chunks(chain, df=_df, targetsize=targetsize) if rawtext is None: rawtext = bytes(bins[0]) bins = bins[1:]