Re: Proposal: Build timers

[zimoun]

Hi,

On Mon, 22 Nov 2021 at 22:02, Jacob Hrbek <kreyren@rixotstudio.cz> wrote:

> See the proposal in https://git.dotya.ml/guix.next/GUIX.next/issues/5

If I understand well your proposal, you are suggesting to attach a value
’build time’.  While I understand it could be useful for monitoring;
especially CI (Cuirass or Build Coordinator) – but it appears useless
for your use case.  Where do you want to attach such value?  I think it
is not affordable to add another field (or ’properties’) for all the
packages.

When discussing the Cuirass revamp, it had been mentioned to grab the
Cuirass database and then try some analytics to infer heuristics helping
for a better scheduling strategy.  However, the task is not as easy as
it appears at first.  Some builds are blocked by unrelated IO
operations, e.g., [1], thus it is hard to distinguish between a
regression or something unexpected in the build farms.  Something useful
for monitoring, but hard to exploit for local builds, IMHO.

Other said, the “telemetry“ you are suggesting require non-trivial
filtering to gain the robust feature you expect, again IMHO.

Last, build-time depends on the environment (how the machine is
stressed), and for instance, I do not want to stop a build because on
average people are building it using X time when my machine builds it
today using X+y time (because it is CPU stressed by something else or
whatever).  Well, I am doubtful that the standard error would not be too
much compared to the mean; other said, my guess is a flat Gaussian
function because of heterogeneous hardware and various levels of stress
for the same build.

To be explicit, I do not think Guix should take care of this.  From my
opinion, if the build farm does not have the substitute (guix weather),
it is a bad sign the package will build locally; therefore, if resources
are limited, before building locally, I would inspect the output of
build farms (ci.guix.gnu.org and bordeaux.guix.gnu.org).  Obviously, it
depends your target architecture and some are poorly supported, sadly.


1: <http://issues.guix.gnu.org/issue/51787>


Cheers,
simon