Yocto build tunables and their hidden costs
Every Yocto user eventually copies the same handful of tunables into local.conf to make builds bearable. ccache, a parallelism bump, a longer fetch timeout, a couple of PREMIRROR lines, an image-features prune. The recipe gets passed around in chat, lands on a wiki, gets forked into a layer. What rarely gets passed around is the failure mode each line buys you. Every one of these knobs swaps “slow” for “different failure mode”, and the new mode shows up at the worst possible time - mid-fetch on a CI runner, or at link time when the box runs out of memory. ...