perf: add threading capability to perfbdiff
Since we are releasing the GIL during diffing, it is interesting to see how a
thread pool would perform on diffing. We add a new `--threads` argument to
commands. Synchronizing the thread pool is a bit complex because we want to be
able to reuse it from one run to another.
On my computer (i7 with 4 cores + hyperthreading), I get the following data for
about 12000 revisions:
threads wall comb wall gain comb overhead
none 31.596715 31.59 0.00% 0.00%
1 31.621228 31.62 -0.08% 0.09%
2 16.406202 32.8 48.08% 3.83%
3 11.598334 34.76 63.29% 10.03%
4 9.205421 36.77 70.87% 16.40%
5 8.517604 42.51 73.04% 34.57%
6 7.94645 47.58 74.85% 50.62%
7 7.434972 51.92 76.47% 64.36%
8 7.070638 55.34 77.62% 75.18%
Compared to the feature disabled (threads=0), the overhead is negligible with
the threading code (threads=1), and the gain is already 48% with two threads.
#require execbit
b51a8138292a introduced a regression where we would mention in the
changelog executable files added by the second parent of a merge. Test
that that doesn't happen anymore
$ hg init repo
$ cd repo
$ echo foo > foo
$ hg ci -qAm 'add foo'
$ echo bar > bar
$ chmod +x bar
$ hg ci -qAm 'add bar'
manifest of p2:
$ hg manifest
bar
foo
$ hg up -qC 0
$ echo >> foo
$ hg ci -m 'change foo'
created new head
manifest of p1:
$ hg manifest
foo
$ hg merge
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ chmod +x foo
$ hg ci -m 'merge'
this should not mention bar but should mention foo:
$ hg tip -v
changeset: 3:c53d17ff3380
tag: tip
parent: 2:ed1b79f46b9a
parent: 1:d394a8db219b
user: test
date: Thu Jan 01 00:00:00 1970 +0000
files: foo
description:
merge
$ hg debugindex bar
rev offset length ..... linkrev nodeid p1 p2 (re)
0 0 5 ..... 1 b004912a8510 000000000000 000000000000 (re)
$ cd ..