Tonight I ran across jdupes which I had not seen before. It is a fork of the venerable fdupes with quite a few performance improvements. Performance?! Well I had to try it of course. Here are a few runs of jdupes and dupd on my home directory for comparison (using -A to skip hidden files which is the default in dupd):

% repeat 5 time ./jdupes -r $HOME -A  > out
Examining 164413 files, 22108 dirs (in 1 specified)
./jdupes -r $HOME -A > out  3.06s user 10.96s system 99% cpu 14.156 total
Examining 164413 files, 22108 dirs (in 1 specified)
./jdupes -r $HOME -A > out  3.07s user 10.82s system 99% cpu 14.029 total
Examining 164413 files, 22108 dirs (in 1 specified)
./jdupes -r $HOME -A > out  3.00s user 11.01s system 99% cpu 14.156 total
Examining 164413 files, 22108 dirs (in 1 specified)
./jdupes -r $HOME -A > out  3.22s user 11.03s system 98% cpu 14.414 total
Examining 164413 files, 22108 dirs (in 1 specified)
./jdupes -r $HOME -A > out  3.04s user 10.87s system 99% cpu 14.042 total

So, consistently about 14 seconds.

% repeat 5 time dupd scan -p $HOME -q
dupd scan -p $HOME -q  3.99s user 6.76s system 139% cpu 7.691 total
dupd scan -p $HOME -q  4.16s user 6.28s system 140% cpu 7.416 total
dupd scan -p $HOME -q  4.13s user 6.53s system 141% cpu 7.540 total
dupd scan -p $HOME -q  3.98s user 6.39s system 139% cpu 7.405 total
dupd scan -p $HOME -q  4.00s user 6.44s system 140% cpu 7.404 total

About 7.5 seconds, or just under that, for dupd.

I still have a handful of ideas to make dupd faster, as I find some spare time I’ll try them out.