linux-kernel - Re: [tip:x86/urgent] x86/cpufeature: Add AVX512_4VNNIW and AVX512

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Message-ID: <20161016224258.e2jen3qkoo3m6qd7@pd.tnic>
Date:   Mon, 17 Oct 2016 00:42:58 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     hpa@...or.com
Cc:     Ingo Molnar <mingo@...nel.org>, peterz@...radead.org,
        tglx@...utronix.de, dave.hansen@...el.com,
        torvalds@...ux-foundation.org, piotr.luc@...el.com,
        luto@...nel.org, brgerst@...il.com, linux-kernel@...r.kernel.org,
        dvlasenk@...hat.com, jpoimboe@...hat.com,
        linux-tip-commits@...r.kernel.org
Subject: Re: [tip:x86/urgent] x86/cpufeature: Add AVX512_4VNNIW and
 AVX512_4FMAPS features

On Sun, Oct 16, 2016 at 11:42:26AM -0700, hpa@...or.com wrote:
> It's needlessly adding complexity for no reason, at least for the

What complexity? The init_scattered_cpuid_features() version is a
trivial patch in comparison to the current version.

> leaves that are going to add bits over time.

Sure, except they don't get added or we don't need them or whatever, and
we end up with only a small number of bits actually being used.

I don't mind moving them to x86_capability later, when a high percentage
of the respective leaf is actually being used but not for a couple of
bits. That's just waste.

> The x86_capability array is not an expensive resource.

0.1% here, 0.1% there, the creeping bloat thing.

And again, the init_scattered_cpuid_features() hunk is much smaller.

-- 
Regards/Gruss,
    Boris.

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