From: ludo@gnu.org (Ludovic Courtès)
To: guix-devel@gnu.org
Subject: Optimizing profile creation
Date: Mon, 02 Sep 2013 23:14:27 +0200 [thread overview]
Message-ID: <874na33ozw.fsf@gnu.org> (raw)
At the GHM, Andreas rightfully noted that building a profile with many
files, as is the case when TeX Live is installed, can take quite a bit
of time; and every time a package is installed/removed/upgraded, you pay
that price again since the profile is built from scratch.
Creating a profile builds a symlink forest that is the union of all the
package directories that make up the profile. But with a package like
TeX Live, until now, this would end up traversing all of its ‘texmf’
sub-directory, just to create a symlink forest that copies the ‘texmf’
directory structure.
So, commit 43dd920 does the (now obvious) optimization: if a
sub-directory, like ‘texmf’, is only in one package, then it symlinks
that directory without traversing it.
This happens to be a quite frequent situation. For instance, with Emacs
in my profile, I would before have this:
--8<---------------cut here---------------start------------->8---
$ ls -l /nix/var/nix/profiles/per-user/ludo/guix-profile-104-link/share/emacs/
total 16
dr-xr-xr-x 6 root nixbld 4096 Jan 1 1970 24.3/
dr-xr-xr-x 3 root nixbld 12288 Jan 1 1970 site-lisp/
$ ls -l /nix/var/nix/profiles/per-user/ludo/guix-profile-104-link/share/emacs/24.3/lisp/
total 2096
lrwxrwxrwx 1 nixbld1 nixbld 87 Jan 1 1970 abbrev.elc -> /nix/store/f3pxa96mg8ws4kfldzarayd8i58ddz5j-emacs-24.3/share/emacs/24.3/lisp/abbrev.elc
lrwxrwxrwx 1 nixbld1 nixbld 89 Jan 1 1970 abbrev.el.gz -> /nix/store/f3pxa96mg8ws4kfldzarayd8i58ddz5j-emacs-24.3/share/emacs/24.3/lisp/abbrev.el.gz
lrwxrwxrwx 1 nixbld1 nixbld 86 Jan 1 1970 align.elc -> /nix/store/f3pxa96mg8ws4kfldzarayd8i58ddz5j-emacs-24.3/share/emacs/24.3/lisp/align.elc
lrwxrwxrwx 1 nixbld1 nixbld 88 Jan 1 1970 align.el.gz -> /nix/store/f3pxa96mg8ws4kfldzarayd8i58ddz5j-emacs-24.3/share/emacs/24.3/lisp/align.el.gz
[...]
--8<---------------cut here---------------end--------------->8---
With this optimization, I have directly this:
--8<---------------cut here---------------start------------->8---
$ ls -l /nix/var/nix/profiles/per-user/ludo/guix-profile-105-link/share/emacs/
total 16
lrwxrwxrwx 1 nixbld1 nixbld 71 Jan 1 1970 24.3 -> /nix/store/f3pxa96mg8ws4kfldzarayd8i58ddz5j-emacs-24.3/share/emacs/24.3/
dr-xr-xr-x 2 root nixbld 12288 Jan 1 1970 site-lisp/
--8<---------------cut here---------------end--------------->8---
No need to traverse the crowded ‘24.3’ directory since there’s only one
package in my profile that provides it.
Please report any speedups or bugs you may have. :-)
Ludo’.
next reply other threads:[~2013-09-02 21:19 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-09-02 21:14 Ludovic Courtès [this message]
2013-09-03 15:51 ` Optimizing profile creation Andreas Enge
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