joerg.sonnenberger created this revision. Herald added a reviewer: hg-reviewers. Herald added a subscriber: mercurial-patches.
REVISION SUMMARY In preperation for updating the reverse-branch-cache incrementally whenever a new changeset comes in, avoid bad performance on resize with Python 3.7 (and likely other 3.x versions). REPOSITORY rHG Mercurial BRANCH default REVISION DETAIL https://phab.mercurial-scm.org/D9778 AFFECTED FILES mercurial/branchmap.py CHANGE DETAILS diff --git a/mercurial/branchmap.py b/mercurial/branchmap.py --- a/mercurial/branchmap.py +++ b/mercurial/branchmap.py @@ -566,6 +566,7 @@ # [4 byte hash prefix][4 byte branch name number with sign bit indicating open] _rbcrecfmt = b'>4sI' _rbcrecsize = calcsize(_rbcrecfmt) +_rbcmininc = 64 * _rbcrecsize _rbcnodelen = 4 _rbcbranchidxmask = 0x7FFFFFFF _rbccloseflag = 0x80000000 @@ -730,11 +731,15 @@ if rev == nullrev: return rbcrevidx = rev * _rbcrecsize - if len(self._rbcrevs) < rbcrevidx + _rbcrecsize: - self._rbcrevs.extend( - b'\0' - * (len(self._repo.changelog) * _rbcrecsize - len(self._rbcrevs)) - ) + requiredsize = rbcrevidx + _rbcrecsize + rbccur = len(self._rbcrevs) + if rbccur < requiredsize: + # bytearray doesn't allocate extra space at least in Python 3.7. + # When multiple changesets are added in a row, precise resize would + # result in quadratic complexity. Overallocate to compensate by + # use the classic doubling technique for dynamic arrays instead. + # If there was a gap in the map before, less space will be reserved. + self._rbcrevs.extend(b'\0' * max(_rbcmininc, requiredsize)) pack_into(_rbcrecfmt, self._rbcrevs, rbcrevidx, node, branchidx) self._rbcrevslen = min(self._rbcrevslen, rev) To: joerg.sonnenberger, #hg-reviewers Cc: mercurial-patches, mercurial-devel _______________________________________________ Mercurial-devel mailing list Mercurial-devel@mercurial-scm.org https://www.mercurial-scm.org/mailman/listinfo/mercurial-devel
