Re: [PATCH v3 0/5] Improving apt cache

["Roberto A. Foglietta" <roberto.foglietta@gmail.com>]

On Mon, 30 Jan 2023 at 09:45, Moessbauer, Felix
<felix.moessbauer@siemens.com> wrote:
>
> On Fri, 2023-01-20 at 08:31 +0100, Uladzimir Bely wrote:
> > Currently, apt cache (e.g. `var/cache/apt/archives`) import and
> > export
> > functions are not optimal. Multiple files are copied from global
> > DL_DIR to package WORKDIR, increasing disk IO and space needed.
> >
> > Also, various chroots (bootstrap, buildchroot, sbuild chroot) include
> > their apt caches to sstate cache files.
> >
> > This patchset switches to hardlinks instead of copies and removes apt
> > cache from bootstrapped images ans sstate caches.
>
> I just saw that this pattern does NOT work in case the cache is on a
> different filesystem. This unfortunately is the case for all CI systems
> with locally mounted caches, as well as for kas-container builds with
> DL_DIR outside the KAS_WORK_DIR.

The entire cache system needs to be reworked and this was pretty
clear. However, every step (hard link included) brings us nearer to
this conclusion and moreover it helps to reduce the building time (now
11m29s on complete image) that allows us to perform more tests in less
and lesser time. I am currently on this and I have a good feeling that
I will reach a general solution soon. As you can imagine the cash
system is not an easy piece to rework due to its implications in many
different starting points it can have. So, build and rebuild are just
two basic cases but variations of the top or ISAR layers that cause a
partial rebuilding and breaks in building are many other cases.
Obviously the main idea is to reach a reasonable goal AND then break
it in several small steps that can be integrated upstream because a
single large patch would be equivalent to fork another 'next' branch
which is possible but IHMO not acceptable for a long time. After all,
also the GPLv3 on composition is not a long-term way to go. So, in the
best case it makes sense that we reach the common goal to rationalise
and speed-up the cache subsystem.

Best regards, R-