Re: master afc0bfd380: Speed up loaddefs-generate on slow disks

[Lars Ingebrigtsen]

Mattias Engdegård <mattiase@acm.org> writes:

> Thank you! I picked a few edges that looked like transitions to a
> higher plateau and tried to find the culprit in the logs, but it's
> really hard. There are many commits and nothing obvious stands out.

Darn.

> Things that might make it easier (speculating here):
>
> * add commit hashes to the points in the graphs because Git dates are
> a bit ambiguous: are they author or commit date, what time of day are
> we talking about, what time zone, etc

I don't know either, really, but my loop is basically doing:

git checkout `git rev-list -1 --before="Mon 30 May 2022 12:00:00 AM UTC" HEAD`

And I don't think that's ambiguous for git -- it'll check out the same
revision every time, I think?  But I may well be wrong.

> * higher resolutions for selected periods (requires more build
> runs). Ideally one per commit but that would require vast amounts of
> time and be very noisy (many botched builds), but perhaps one per day?

I can do that, but it'll take one week to run for the same time period
(since I need to run each day three times to pick a median build time --
otherwise it's too noisy).

But perhaps I could run it daily in periods of specific interest?

> It would be very useful if we could have an automatic (or
> semi-automatic) daily build monitoring performance like this, perhaps
> even running benchmarks.

Yes, indeed.  But the build servers we have seem to struggle with
building Emacs even normally -- they seem to be woefully
under-provisioned, and I'd guess that any timing data from them would
just be noise.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no