Graft slowness fixed

[Ludovic Courtès]

Hi Thomas,

Thomas Danckaert <address@hidden> skribis:

> There is one issue: when I apply this patch series on current master (after
> commit e10872c gnu: gpgme: Patch CMake files), `guix build kdevelop` seems to
> get stuck after completing the build (at least it doesn't return after running
> at ~100%cpu for over 40minutes, with no output).  When I apply the patch
> series on commit 4d0a3d8 (system: grub: Load relevant EFI modules on EFI
> systems), I don't have this problem.  I'm not sure if this is an issue just on
> my system, or not (I upgraded guix-daemon to lastest master, but the problem
> remains). Hints on how to investigate this are welcome!

You found a terrrrrible issue that somehow went unnoticed for two weeks!

This cute commit:

  
http://git.savannah.gnu.org/cgit/guix.git/commit/?id=d38bc9a9f6feefc465964531520fee5663a12f48

had the effect of disabling caching in the DAG traversal performed by
‘graft-derivation’.  For big DAGs like that of kdevelop, you could
really feel it.  :-)

This is fixed by this one-liner:

  
http://git.savannah.gnu.org/cgit/guix.git/commit/?id=90ad5c8836138b7fd4d1bd0243dfa8b30ae0cf21

This other one fixes a related issue that had always been there apparently:

  
http://git.savannah.gnu.org/cgit/guix.git/commit/?id=0aeed5e310504a9ef2cf6a2b2a7e76086eb8c2fc

Thanks for the heads-up!

Ludo’.