I'm pretty sure that -jN (where N > 1) will be a net win on most of our tinderboxes. We should test this theory on the try server first.
what happened when you ran this on tryserver? Which -j"N" seemed best in a VM?
Here are some results from try server: linux mac windows -j1 1:09 (1) 1:10 0:54 (2) 1:10 1:53 (2) 0:46 (3) 1:44 (3) -j4 0:57 (1) 0:42 2:27 (1) 0:55 (2) 0:42 1:34 (2) 0:44 (3) 0:44 1:33 (3) The number in parentheses is the slave number that ran the build. There's only one mac slave doing try builds right now. The make option was added by uploading a custom mozconfig to try server that had 'mk_add_options MOZ_MAKE_FLAGS="-jN"'. These results show that -j4 is a win on mac and windows, and not much of a win on linux (but it doesn't hurt). Interestingly the mac is already using -j4 on try server.
Created attachment 350146 [details] [diff] [review] Enable -j4 on staging
Comment on attachment 350146 [details] [diff] [review] Enable -j4 on staging changeset: 541:a753975e2bb6
We've been running with -j4 for a while in production now. Closing this out.