Re: Architecture baseline for Forky

On 12/11/25 at 20:27 +0200, Adrian Bunk wrote:
> On Wed, Nov 05, 2025 at 08:42:08PM +0100, Lucas Nussbaum wrote:
> > Hi,
> 
> Hi Lucas,
> 
> > On 26/10/25 at 13:21 +0100, Bastian Blank wrote:
> > > Hi
> > > 
> > > We never did a real discussion about architecture baselines before, but I think
> > > we should do that.  We also don't have any guidelines what we as Debian want to
> > > actually support.  But given that we are a general purpose distribution, we
> > > have to find a balance.
> > 
> > This thread only discusses bumping baselines, but I wonder if we should
> > consider other ways to provide architecture-optimized versions of some
> > packages?
> >...
> 
> I did already discuss in [1] two additional topics, that should be 
> prerequisites for any productive discussion:
> 
> 1. Lack of data
> 
> I have not seen any data discussed here on the benefits that could be a 
> basis for an actual discussion.
> 
> Like what are the actual performance differences between v1/v2/v3/v4
> on amd64?
> 
> Which steps (if any) bring large performance improvements?
> Are these performance improvements for everything and/or are there
> large benefits that are limited to few packages?
> 
> I do remember how 20 years ago when Gentoo was new, people spent days 
> watching their computer compiling everything perfectly optimized for
> their system - only to discover that it didn't make a noticeable 
> difference.
> 
> 2. Don't restrict the discussion/data to architecture baselines
> 
> How much performance does security hardening cost?
> What are the performance and size effects of building packages
> optimized for size instead of speed?
> What performance benefits would making x32 a (partial?) release
> architecture bring?
> ...
> 
> We are already providing a non-PIE version of the Python interpreter for 
> users who need it for performance reasons, and it is for example 
> possible that the benefits of providing packages without hardening (for 
> situations where hardening is not necessary) might bring larger benefits 
> than architecture-optimized versions.
> 
> Would x32 optimized for v3 be the best option for many use cases?
> 
> Any discussion of possible solutions has to start with data showing what 
> changes might actually bring sufficient benefits for being worth the 
> effort.

Right.

There are some benchmarks results at https://www.phoronix.com/review/ubuntu-x86-64-v3-benchmark

Also, there are at least 4 criterias to evaluate solutions:
- performance gain
- loss of HW support
- per-package work needed (hwcaps is bad for this)
- archive/mirror impact (architecture variant is bad for this)

A tentative summary:

| Solution             | Performance | HW support | Pkg maint work | Archive size |
| -------------------- | ----------- | ---------- | -------------- | ------------ |
| baseline bump        | +++         | ---        | little impact  | no impact    |
| architecture variant | +++         | no impact  | little impact  | ---          |
| per-pkg solutions    | +           | no impact  | ---            | no impact    |


Lucas