Re: x86_64-v2 in Fedora

[Stephen John Smoogen <smooge@xxxxxxxxx>]

On Tue, 15 Jun 2021 at 17:35, Neal Gompa <ngompa13@xxxxxxxxx> wrote:

Hey all,

Earlier this week, I was helping with processing features for openSUSE
Leap 15.4[1] and I discovered that they're planning on introducing
x86_64-v2 to openSUSE soon. The reference for this change was that
RHEL 9 is going to use x86_64-v2[2]. Additionally, other distributions
have been considering bumping up to v2 or v3[3][4].

Wasn't the last time this was looked at was https://fedoraproject.org/wiki/Changes/x86-64_micro-architecture_update? That spawned the multi hundred thread "Fedora 32 System-Wide Change proposal: x86-64 micro-architecture update" but I think this was to push towards level 3. However my review of that thread and some others seemed to show there was no stomach to move Fedora up without many people dropping packages etc.

I used this https://unix.stackexchange.com/questions/631217/how-do-i-check-if-my-cpu-supports-x86-64-v2 to see what cpu instructions are at each level

```

#!/usr/bin/awk -f

BEGIN {
    while (!/flags/) if (getline < "/proc/cpuinfo" != 1) exit 1
    if (/lm/&&/cmov/&&/cx8/&&/fpu/&&/fxsr/&&/mmx/&&/syscall/&&/sse2/) level = 1
    if (level == 1 && /cx16/&&/lahf/&&/popcnt/&&/sse4_1/&&/sse4_2/&&/ssse3/) level = 2
    if (level == 2 && /avx/&&/avx2/&&/bmi1/&&/bmi2/&&/f16c/&&/fma/&&/abm/&&/movbe/&&/xsave/) level = 3
    if (level == 3 && /avx512f/&&/avx512bw/&&/avx512cd/&&/avx512dq/&&/avx512vl/) level = 4
    if (level > 0) { print "CPU supports x86-64-v" level; exit level + 1 }
    exit 1
}

```

level 2 is avx and avx2 plus some others.

 

Some cursory examination of the new x86_64 sublevels seem to indicate
that x86_64-v2 goes back to roughly 2007~2008, merely cutting off the
first couple of generations of x86_64 CPUs from Intel and AMD. I
personally don't have any computers that don't have support for
x86_64-v2 anymore.

Does anyone know if anyone is planning to propose this for Fedora
anytime soon, either as an addon architecture (like what Arch is
doing) or an upgrade of our x86_64 baseline like RHEL is doing?

[1]: https://en.opensuse.org/Feature_Planning_15.4
[2]: https://developers.redhat.com/blog/2021/01/05/building-red-hat-enterprise-linux-9-for-the-x86-64-v2-microarchitecture-level
[3]: https://ml.mageia.org/l/arc/dev/2021-02/msg00583.html
[4]: https://www.phoronix.com/scan.php?page=news_item&px=Arch-Linux-x86-64-v3-Port-RFC

--
真実はいつも一つ！/ Always, there's only one truth!
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--

Stephen J Smoogen.
I've seen things you people wouldn't believe. Flame wars in sci.astro.orion. I have seen SPAM filters overload because of Godwin's Law. All those moments will be lost in time... like posts on  BBS... time to reboot.

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