[tbb-dev] Very very slow tor-browser-build build; catastrophic recursion in rbm?

[Matthew Finkel]

On Tue, Feb 11, 2020 at 11:45:26PM -0700, David Fifield wrote:
> I did a build of tor-browser-build build and it took even longer than I
> remember it taking -- from Friday until Tuesday, roughly. This is on a
> VPS with six 2 GHz CPUs and 16 GB RAM. Some projects I know take a long
> time to build, like rust and firefox, but it seemed like most of the
> time was being spent in the "rbm" process, not in building the projects.

Hi David,

I've seen this too (although builds taking 2+ days is significantly
worse than I've seen). I was going to talk with Nicolas about this after
our current releases this week. I did some manual debugging on this and
came to roughly the same conclusion, but I still don't know nearly
enough about the internals of the system. I found (what seems like) rbm
searching for the correct build script is very expense.

There is some duplicated work, as well, when dependencies are shared
across projects (and platforms) - but that shouldn't account for much
time overall.

- Matt