Re: Improving the speed of guix time-machine for development environments

[Ludovic Courtès]

Hi Richard,

Richard Sent <richard@freakingpenguin.com> skribis:

>> I think channels listed in channels.scm files should optionally support
>> using whatever channel version is already in the user's profile, if
>> present. This would significantly speed up entering development
>> environments composed of Guix channels.
>
>> Unfortunately, *I may be delayed every time I enter the development
>> environment by several minutes while Guix computes a new derivation
>> due to an update in %default-channels*.

I understand and share the frustration regarding performance.

To address the problem, I would suggest a different route (the problem
with the patch you propose here is that it makes things unpredicatable
and stateful: you’d end up using whatever commit happens to be already
in a profile).

My suggestion would be for ‘guix pull’ to populate the same cache that
‘guix time-machine’ uses.  That way, if you time-travel to a commit you
already have in a profile, it would be instantaneous.

I started looking into it a while back and there were some
complications, but I forgot the details.

WDYT?  Would this be an improvement for you?

Thanks,
Ludo’.