From mboxrd@z Thu Jan  1 00:00:00 1970
From: ludo@gnu.org (Ludovic =?utf-8?Q?Court=C3=A8s?=)
Subject: Re: parallelizing more actions
Date: Sat, 11 Nov 2017 12:25:01 +0100
Message-ID: <878tfdjbw2.fsf@gnu.org>
References: <20171109090559.GF1815@macbook41>
Mime-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: quoted-printable
Return-path: <guix-devel-bounces+gcggd-guix-devel=m.gmane.org@gnu.org>
Received: from eggs.gnu.org ([2001:4830:134:3::10]:40787)
	by lists.gnu.org with esmtp (Exim 4.71)
	(envelope-from <ludo@gnu.org>) id 1eDTuM-0007da-Fe
	for guix-devel@gnu.org; Sat, 11 Nov 2017 06:25:07 -0500
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <ludo@gnu.org>) id 1eDTuL-0001ZV-Ia
	for guix-devel@gnu.org; Sat, 11 Nov 2017 06:25:06 -0500
Received: from hera.aquilenet.fr ([2a01:474::1]:42748)
	by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32)
	(Exim 4.71) (envelope-from <ludo@gnu.org>) id 1eDTuL-0001Yt-Bm
	for guix-devel@gnu.org; Sat, 11 Nov 2017 06:25:05 -0500
In-Reply-To: <20171109090559.GF1815@macbook41> (Efraim Flashner's message of
	"Thu, 9 Nov 2017 11:05:59 +0200")
List-Id: "Development of GNU Guix and the GNU System distribution."
	<guix-devel.gnu.org>
List-Unsubscribe: <https://lists.gnu.org/mailman/options/guix-devel>,
	<mailto:guix-devel-request@gnu.org?subject=unsubscribe>
List-Archive: <http://lists.gnu.org/archive/html/guix-devel/>
List-Post: <mailto:guix-devel@gnu.org>
List-Help: <mailto:guix-devel-request@gnu.org?subject=help>
List-Subscribe: <https://lists.gnu.org/mailman/listinfo/guix-devel>,
	<mailto:guix-devel-request@gnu.org?subject=subscribe>
Errors-To: guix-devel-bounces+gcggd-guix-devel=m.gmane.org@gnu.org
Sender: "Guix-devel" <guix-devel-bounces+gcggd-guix-devel=m.gmane.org@gnu.org>
To: Efraim Flashner <efraim@flashner.co.il>
Cc: guix-devel@gnu.org

Hi Efraim,

Efraim Flashner <efraim@flashner.co.il> skribis:

> While rebuilding glibc-final on aarch64 I realized that the 'strip phase
> took 235 seconds. The relevant code for 'strip from gnu-build-system is
> in guix/build/gnu-build-system.scm, starting at line 340, with the
> actual stripping starting at 398. When I changed 'for-each' to
> 'par-for-each' the time dropped from 235 seconds to 215, about an 8.5%
> savings. I'm pretty sure most of that time was spent failing to strip
> certain files, but it is still a savings.

Is it on a spinning hard disk or an SSD?  My guess is that most of the
time is I/O, and that parallelizing doesn=E2=80=99t buy us much (indeed, 8.=
5% is
not that much, far from a linear speedup.)=20

So I=E2=80=99m mildly reluctant to parallelizing this particular piece of c=
ode.

Thanks,
Ludo=E2=80=99.