Gentoo Archives: gentoo-dev

From: Andrew Savchenko <bircoph@g.o>
To: gentoo-dev@l.g.o
Subject: Re: [gentoo-dev] Gentoo i486 support
Date: Sat, 25 Aug 2018 11:08:00
In Reply to: Re: [gentoo-dev] Gentoo i486 support by Rich Freeman
1 Hi!
3 On Wed, 22 Aug 2018 09:08:06 -0400 Rich Freeman wrote:
4 > On Wed, Aug 22, 2018 at 8:26 AM Ben Kohler <bkohler@g.o> wrote:
5 > >
6 > > 1) Adjust x86 profile defaults to drop the problematic -march=i686.
7 > > This would be more in line with amd64 profiles (et al), which set no
8 > > -march value so it can run on any hardware for this arch.
9 > >
10 >
11 > My knee-jerk reaction was that this is a bad idea, but after a bit of
12 > thought there are some arguments in favor of this:
13 >
14 > First, the argument against: i386 is VERY old. Most distros moved
15 > their defaults to i686 because it had significant improvements, and
16 > i686 was still mainstream but i386 was ancient. In contrast with
17 > amd64 the entire architecture is fairly new and the baseline doesn't
18 > suffer from many of the issues i386 suffers compared to i686. This is
19 > a really short synopsis - if you go to any distro list archive you can
20 > find long passionate arguments from ~10 years ago that elaborated on
21 > this. In that sense, going back to i386 is turning back the clock.
22 >
23 > HOWEVER, I think there is an argument for i386 that wasn't so valid
24 > back then. x86 in general is starting to look a bit like i386. What
25 > are the main use cases for it in this day and age? I don't use x86,
26 > so I'm not the best person to answer that. However, I'd broadly split
27 > it into two categories (mostly by tautology):
28 >
29 > 1. Museum hardware. People have systems that are running simply
30 > BECAUSE they are old, not because they are cost-effective/etc. I'm
31 > not sure I'd even lump used hardware into this category any longer, as
32 > I'm sure there are plenty of i686+ used PCs at rock-bottom prices
33 > already out there, and maintaining pre-Y2K hardware is going to be
34 > fairly painful. For this use case i386 as the baseline makes a LOT of
35 > sense.
36 >
37 > 2. Non-museum hardware. People have x86 hardware because it is the
38 > most cost-effective solution for a task, and not merely because it is
39 > old. IMO for this use case i686 makes a lot more sense as a baseline.
40 > However, I'm honestly not sure in this day and age what these use
41 > cases even are, unless it is something you can buy for $10 at a flea
42 > market. Even if you're talking about a container running one
43 > application that only needs 500kB of RAM, is there really that much
44 > benefit to not building it for amd64?
46 As active x86 hardware user I can add:
48 3. Security. CPUs without speculative execution and L3 cache are
49 much more secure by design. Thanks to the virtues of Gentoo
50 (highest possible code optimization and ability to USE light
51 versions of applications) such hardware (e.g. 32bit Atoms) is still
52 usable quite fine.
54 Best regards,
55 Andrew Savchenko