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
$ rm -rf a
$ hg init a
$ cd a
$ echo foo > foo
$ hg ci -qAm0
$ echo toremove > toremove
$ echo todelete > todelete
$ chmod +x foo toremove todelete
$ hg ci -qAm1
Test that local removed/deleted, remote removed works with flags
$ hg rm toremove
$ rm todelete
$ hg co -q 0
$ echo dirty > foo
$ hg up -c
abort: uncommitted changes
[255]
$ hg up -q
$ cat foo
dirty
$ hg st -A
M foo
C todelete
C toremove
Validate update of standalone execute bit change:
$ hg up -C 0
1 files updated, 0 files merged, 2 files removed, 0 files unresolved
$ chmod -x foo
$ hg ci -m removeexec
nothing changed
[1]
$ hg up -C 0
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg up
3 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg st
$ cd ..