Mercurial > hg
view tests/svn-safe-append.py @ 17970:0b03454abae7
ancestor: faster algorithm for difference of ancestor sets
One of the major reasons rebase is slow in large repositories is
the computation of the detach set: the set of ancestors of the
changesets to rebase not in the destination parent. This is currently
done via a revset that does two walks all the way to the root of
the DAG. Instead of doing that, to find ancestors of a set <revs>
not in another set <common> we walk up the tree in reverse revision
number order, maintaining sets of nodes visited from <revs>, <common>
or both.
For the common case where the sets are close both topologically and
in revision number (relative to repository size), this has been
found to speed up rebase by around 15-20%. When the nodes are farther
apart and the DAG is highly branching, it is harder to say which
would win.
Here's how long computing the detach set takes in a linear repository
with over 400000 changesets, rebasing near tip:
Rebasing across 4 changesets
Revset method: 2.2s
New algorithm: 0.00015s
Rebasing across 250 changesets
Revset method: 2.2s
New algorithm: 0.00069s
Rebasing across 10000 changesets
Revset method: 2.4s
New algorithm: 0.019s
author | Siddharth Agarwal <sid0@fb.com> |
---|---|
date | Mon, 26 Nov 2012 11:46:51 -0800 |
parents | c1b47c0fd2b6 |
children | bdba6a2015d0 |
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#!/usr/bin/env python __doc__ = """Same as `echo a >> b`, but ensures a changed mtime of b. Without this svn will not detect workspace changes.""" import sys, os text = sys.argv[1] fname = sys.argv[2] f = open(fname, "ab") try: before = os.fstat(f.fileno()).st_mtime f.write(text) f.write("\n") finally: f.close() inc = 1 now = os.stat(fname).st_mtime while now == before: t = now + inc inc += 1 os.utime(fname, (t, t)) now = os.stat(fname).st_mtime