Mercurial > hg-stable
view tests/blackbox-readonly-dispatch.py @ 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 | 0767c2f624c6 |
children | 853bf7d90804 |
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from __future__ import absolute_import, print_function import os from mercurial import ( dispatch, ) def testdispatch(cmd): """Simple wrapper around dispatch.dispatch() Prints command and result value, but does not handle quoting. """ print("running: %s" % (cmd,)) req = dispatch.request(cmd.split()) result = dispatch.dispatch(req) print("result: %r" % (result,)) # create file 'foo', add and commit f = open('foo', 'wb') f.write('foo\n') f.close() testdispatch("add foo") testdispatch("commit -m commit1 -d 2000-01-01 foo") # append to file 'foo' and commit f = open('foo', 'ab') f.write('bar\n') f.close() # remove blackbox.log directory (proxy for readonly log file) os.rmdir(".hg/blackbox.log") # replace it with the real blackbox.log file os.rename(".hg/blackbox.log-", ".hg/blackbox.log") testdispatch("commit -m commit2 -d 2000-01-02 foo") # check 88803a69b24 (fancyopts modified command table) testdispatch("log -r 0") testdispatch("log -r tip")