From mboxrd@z Thu Jan  1 00:00:00 1970
From: ludo@gnu.org (Ludovic =?utf-8?Q?Court=C3=A8s?=)
Subject: Graft slowness fixed
Date: Mon, 16 Jan 2017 22:18:55 +0100
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References: <1484159585-12289-1-git-send-email-thomas.danckaert@gmail.com>
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	(Thomas Danckaert's message of "Wed, 11 Jan 2017 19:33:01 +0100")
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To: Thomas Danckaert <thomas.danckaert@gmail.com>
Cc: guix-devel@gnu.org

Hi Thomas,

Thomas Danckaert <thomas.danckaert@gmail.com> skribis:

> There is one issue: when I apply this patch series on current master (aft=
er
> commit e10872c gnu: gpgme: Patch CMake files), `guix build kdevelop` seem=
s to
> get stuck after completing the build (at least it doesn't return after ru=
nning
> 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 ju=
st on
> my system, or not (I upgraded guix-daemon to lastest master, but the prob=
lem
> 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=3Dd38bc9a9f6feefc465=
964531520fee5663a12f48

had the effect of disabling caching in the DAG traversal performed by
=E2=80=98graft-derivation=E2=80=99.  For big DAGs like that of kdevelop, yo=
u could
really feel it.  :-)

This is fixed by this one-liner:

  http://git.savannah.gnu.org/cgit/guix.git/commit/?id=3D90ad5c8836138b7fd4=
d1bd0243dfa8b30ae0cf21

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

  http://git.savannah.gnu.org/cgit/guix.git/commit/?id=3D0aeed5e310504a9ef2=
cf6a2b2a7e76086eb8c2fc

Thanks for the heads-up!

Ludo=E2=80=99.