[Nix-dev] enableParallelbuilding for many packages

[Vladimír Čunát]

On 10/26/2012 12:36 AM, Marc Weber wrote:
> Buildfarm: You're wrong and you know it. Parallelizing nix builds is
> easy (scaling horizontally) - You can write your own Amazon buildfarm
> within one day which scales automatically probably. The problem is "time
> to get a new build" - and for that (security updates etc) making each
> build go as fast as possible is required.

Yes, sure, but that would be a completely different case. Hopefully we 
will have *where* to scale in future.

I was only considering the "hydra.nixos.org" build farm. That one can 
AFAIK run about 15-20 threads and builds several platforms (usually 2 
but sometimes as much as 7).

But I see no problem in updating the packages. It is easy to globally 
disable anyway if anyone minds. I just hope that the probability of 
producing a bad result *without failing the build* is very small...

> The more packages and dependencies - the longer will nix take - the
> greater the impact using nixos vs other distros (where you can recompile
> something in between and everything will pick it up)

True, this could be a problem for security updates on some critical 
systems. There I would even consider re-linking without rebuilding as in 
other distros. For minor bugfixes this shouldn't give a different result 
(in that case it would be good to modify the way we create package hashes).

> You're right that the goal is to make getting some particular builds for
> testing faster, too.
>
> ./configure is taking much time - anwyay. Don't think rewriting most
> packages to use cmake would be an option (and some cmake Makefiles are
> slower than hand tuned ones - at least I heared about such case)

It seems to me that build time is often only of minor concern upstream. 
It's somehow expected that update cycles (excluding security updates) 
take months at least...


Vlada


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