Re: [Nix-dev] parallel make
Hi Michael, I would sometimes [like to] try to build my system with maximum parallel building enabled just to record what breaks this time. yes, it would be great if that were possible. As of today, the only way to enable parallel building for all packages is to override the default for enableParallelBuilding in the generic builder, but if you do that you'll end up with a different stdenv. That is unsatisfactory. If /etc/nix/nix.conf would offer an option to determine the default value of enableParallelBuilding, then we could have the best of both worlds. By default, parallel building would be enabled only for those packages that explicitly request it. For the purposes of testing and development, however, one could flip the switch and have parallel building enabled for all packages that don't explicitly disable it. In other words, users would be able to switch between opt-in and opt-out. Best regards, Peter ___ nix-dev mailing list nix-dev@lists.science.uu.nl http://lists.science.uu.nl/mailman/listinfo/nix-dev
Re: [Nix-dev] parallel make (was: Again: Why don't these people havecommit access)
On 01/21/2015 01:17 AM, Marc Weber wrote: I think we have a documentation issue. There should be flag such as: parallelBuildingPossible = yes/sometimes/no; Yeah, well, I personally leave ``enableParallelBuilding = false;`` if I find it could fail. We could just e.g. have a more aggressive option that would use parallel make unless ``enableParallelBuilding = false;``. Vladimir smime.p7s Description: S/MIME Cryptographic Signature ___ nix-dev mailing list nix-dev@lists.science.uu.nl http://lists.science.uu.nl/mailman/listinfo/nix-dev
[Nix-dev] parallel make (was: Again: Why don't these people have commit access)
Hi Michael, To find out if a makefile is parallel-safe, we need to try it with parallel building enabled. This can only be done package-per-package, I cannot quickly build everything with parallel builds on and then blacklist what fails. the rationale behind that choice is that you cannot easily tell whether a package compiles with parallel make jobs enabled or not. Under-specified make dependencies lead to race conditions, and these may or may not screw up your build. Whether an unsafe build actually fails depends on any number of factors that influence the order in which make schedules the jobs. You can -- in general -- not enable parallel building, run the build once, and conclude that it's safe! The number of false positives is going to be large. Because of this situation, many NixOS contributors preferred the opt-in solution that we have today. The aim of that the double opt-in is *not* to maximize the number of builds that run with parallelism enabled, it is to minimize the number of non-deterministic failures that someone has to debug and worry about. Best regards, Peter ___ nix-dev mailing list nix-dev@lists.science.uu.nl http://lists.science.uu.nl/mailman/listinfo/nix-dev
Re: [Nix-dev] parallel make (was: Again: Why don't these people havecommit access)
How complicated is it to override mkDerivation in nixpkgs passing parallelBuilding = true ? I think we have a documentation issue. There should be flag such as: parallelBuildingPossible = yes/sometimes/no; instead of parallelBuilding = true. Then Michale Raskin's tests would not fail on packages which are known to not build correctly ... Marc Weber ___ nix-dev mailing list nix-dev@lists.science.uu.nl http://lists.science.uu.nl/mailman/listinfo/nix-dev
