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 svn13
$ cat <<EOF >> $HGRCPATH
> [extensions]
> mq =
> [diff]
> nodates = 1
> [subrepos]
> allowed = true
> svn:allowed = true
> EOF
fn to create new repository, and cd into it
$ mkrepo() {
> hg init $1
> cd $1
> hg qinit
> }
handle svn subrepos safely
$ svnadmin create svn-repo-2499
$ SVNREPOPATH=`pwd`/svn-repo-2499/project
#if windows
$ SVNREPOURL=file:///`$PYTHON -c "import urllib, sys; sys.stdout.write(urllib.quote(sys.argv[1]))" "$SVNREPOPATH"`
#else
$ SVNREPOURL=file://`$PYTHON -c "import urllib, sys; sys.stdout.write(urllib.quote(sys.argv[1]))" "$SVNREPOPATH"`
#endif
$ mkdir -p svn-project-2499/trunk
$ svn import -qm 'init project' svn-project-2499 "$SVNREPOURL"
qnew on repo w/svn subrepo
$ mkrepo repo-2499-svn-subrepo
$ svn co "$SVNREPOURL"/trunk sub
Checked out revision 1.
$ echo 'sub = [svn]sub' >> .hgsub
$ hg add .hgsub
$ hg status -S -X '**/format'
A .hgsub
$ hg qnew -m0 0.diff
$ cd sub
$ echo a > a
$ svn add a
A a
$ svn st
A* a (glob)
$ cd ..
$ hg status -S # doesn't show status for svn subrepos (yet)
$ hg qnew -m1 1.diff
abort: uncommitted changes in subrepository "sub"
[255]
$ cd ..