From mboxrd@z Thu Jan  1 00:00:00 1970
From: ludo@gnu.org (Ludovic =?utf-8?Q?Court=C3=A8s?=)
Subject: Re: [PATCH] offload: Memoize the 'machine-load' procedure
Date: Wed, 17 Jun 2015 21:28:35 +0200
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In-Reply-To: <87pp4udwav.fsf@netris.org> (Mark H. Weaver's message of "Wed, 17
	Jun 2015 14:28:08 -0400")
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To: Mark H Weaver <mhw@netris.org>
Cc: guix-devel@gnu.org

Mark H Weaver <mhw@netris.org> skribis:

> This patch memoizes the 'machine-load' procedure so that the load of
> each build slave is queried only once per call to 'guix offload'.  Apart
> from avoiding wasteful repeated ssh connections, this is needed to
> ensure that all calls to the sorting predicate are consistent with each
> other, which is part of the contract with 'sort'.

Good point.

I don=E2=80=99t think we can memoize it globally.  The reason is that
=E2=80=98choose-build-machine=E2=80=99 can return #f when all the machines =
are
overloaded; in that case =E2=80=98guix offload=E2=80=99 returns =E2=80=9Cpo=
stpone=E2=80=9D, and doesn=E2=80=99t
exit.  Instead, it tries again until at least one machine is not
overloaded.

So I think we should memoize =E2=80=98machine-less-loaded-or-faster?=E2=80=
=99 locally in
=E2=80=98choose-build-machine=E2=80=99.

WDYT?

Thanks,
Ludo=E2=80=99.