bug#43564: cuirass: Contention while registering new builds.

[Mathieu Othacehe]

Hey Ludo,

> Isn’t that the real problem, that we’re doing one transaction per
> derivation?

Is it really better in term of performance to send batch of queries
within a single transaction? I haven't tried it yet.

I think that the real bottleneck was having N fibers fighting over 4
workers to execute large number of insertions. Having all those queries
done by workers dedicated to registration in a single pass seems to
improve a lot the situation.

Maybe having those registration workers posting unique transactions
containing all the queries would be even more beneficial.

Thanks,

Mathieu