git-p4: slow doing a commit due to weird perforce behaviour?

Am I just imagining this? It's more of a perforce question than a git question I'm afraid.

git-p4 seems to be quite slow sometimes at submitting changes. At least for me, it seems to be down to the generation of the diff, which is done with "p4 diff -du ...".

If I do "p4 diff ..." or "p4 diff -dc ..." then the response comes back straight away, and seems to be based purely on the currently checked out files.

If instead, though, I do "p4 diff -du" then it appears to do a diff of every file, or something. It's able to spot files that I haven't actually checked out, but is *much* slower.

Does anyone else get this or is it just me?

% time p4 diff -du ...

real 0m9.082s user 0m6.560s sys 0m0.952s

% time p4 diff -dc ... ... - file(s) not opened on this client.

real 0m0.021s user 0m0.000s sys 0m0.000s