Mercurial > hg-stable
view tests/test-import-context.t @ 32200:4d504e541d3d
rebase: use matcher to optimize manifestmerge
The old merge code would call manifestmerge and calculate the complete diff
between the source to the destination. In many cases, like rebase, the vast
majority of differences between the source and destination are irrelevant
because they are differences between the destination and the common ancestor
only, and therefore don't affect the merge. Since most actions are 'keep', all
the effort to compute them is wasted.
Instead, let's compute the difference between the source and the common ancestor
and only perform the diff of those files against the merge destination. When
using treemanifest, this lets us avoid loading almost the entire tree when
rebasing from a very old ancestor. This speeds up rebase of an old stack of 27
commits by 20x.
In mozilla-central, without treemanifest, when rebasing a commit from
default~100000 to default, this speeds up the manifestmerge step from 2.6s to
1.2s. However, the additional diff adds an overhead to all manifestmerge calls,
especially for flat manifests. When rebasing a commit from default~1 to default
it appears to add 100ms in mozilla-central. While we could put this optimization
behind a flag, I think the fact that it makes merge O(number of changes being
applied) instead of O(number of changes between X and Y) justifies it.
author | Durham Goode <durham@fb.com> |
---|---|
date | Wed, 03 May 2017 10:43:59 -0700 |
parents | f2719b387380 |
children | 75be14993fda |
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Test applying context diffs $ cat > writepatterns.py <<EOF > import sys > > path = sys.argv[1] > lasteol = sys.argv[2] == '1' > patterns = sys.argv[3:] > > fp = file(path, 'wb') > for i, pattern in enumerate(patterns): > count = int(pattern[0:-1]) > char = pattern[-1] + '\n' > if not lasteol and i == len(patterns) - 1: > fp.write((char*count)[:-1]) > else: > fp.write(char*count) > fp.close() > EOF $ cat > cat.py <<EOF > import sys > sys.stdout.write(repr(file(sys.argv[1], 'rb').read()) + '\n') > EOF Initialize the test repository $ hg init repo $ cd repo $ python ../writepatterns.py a 0 5A 1B 5C 1D $ python ../writepatterns.py b 1 1A 1B $ python ../writepatterns.py c 1 5A $ python ../writepatterns.py d 1 5A 1B $ hg add adding a adding b adding c adding d $ hg ci -m addfiles Add file, missing a last end of line $ hg import --no-commit - <<EOF > *** /dev/null 2010-10-16 18:05:49.000000000 +0200 > --- b/newnoeol 2010-10-16 18:23:26.000000000 +0200 > *************** > *** 0 **** > --- 1,2 ---- > + a > + b > \ No newline at end of file > *** a/a Sat Oct 16 16:35:51 2010 > --- b/a Sat Oct 16 16:35:51 2010 > *************** > *** 3,12 **** > A > A > A > ! B > C > C > C > C > C > ! D > \ No newline at end of file > --- 3,13 ---- > A > A > A > ! E > C > C > C > C > C > ! F > ! F > > *** a/b 2010-10-16 18:40:38.000000000 +0200 > --- /dev/null 2010-10-16 18:05:49.000000000 +0200 > *************** > *** 1,2 **** > - A > - B > --- 0 ---- > *** a/c Sat Oct 16 21:34:26 2010 > --- b/c Sat Oct 16 21:34:27 2010 > *************** > *** 3,5 **** > --- 3,7 ---- > A > A > A > + B > + B > *** a/d Sat Oct 16 21:47:20 2010 > --- b/d Sat Oct 16 21:47:22 2010 > *************** > *** 2,6 **** > A > A > A > - A > - B > --- 2,4 ---- > EOF applying patch from stdin $ hg st M a M c M d A newnoeol R b What's in a $ python ../cat.py a 'A\nA\nA\nA\nA\nE\nC\nC\nC\nC\nC\nF\nF\n' $ python ../cat.py newnoeol 'a\nb' $ python ../cat.py c 'A\nA\nA\nA\nA\nB\nB\n' $ python ../cat.py d 'A\nA\nA\nA\n' $ cd ..