Re: [tip:x86/urgent] x86/cpufeature: Add AVX512_4VNNIW and AVX512_4FMAPS features
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- Subject: Re: [tip:x86/urgent] x86/cpufeature: Add AVX512_4VNNIW and AVX512_4FMAPS features
- From: "Luc, Piotr" <Piotr.Luc@xxxxxxxxx>
- Date: Mon, 17 Oct 2016 09:55:07 +0000
- Accept-language: en-US
- Cc: "mingo@xxxxxxxxxx" <mingo@xxxxxxxxxx>, "peterz@xxxxxxxxxxxxx" <peterz@xxxxxxxxxxxxx>, "linux-kernel@xxxxxxxxxxxxxxx" <linux-kernel@xxxxxxxxxxxxxxx>, "torvalds@xxxxxxxxxxxxxxxxxxxx" <torvalds@xxxxxxxxxxxxxxxxxxxx>, "tglx@xxxxxxxxxxxxx" <tglx@xxxxxxxxxxxxx>, "linux-tip-commits@xxxxxxxxxxxxxxx" <linux-tip-commits@xxxxxxxxxxxxxxx>, "jpoimboe@xxxxxxxxxx" <jpoimboe@xxxxxxxxxx>, "brgerst@xxxxxxxxx" <brgerst@xxxxxxxxx>, "luto@xxxxxxxxxx" <luto@xxxxxxxxxx>, "Hansen, Dave" <dave.hansen@xxxxxxxxx>, "dvlasenk@xxxxxxxxxx" <dvlasenk@xxxxxxxxxx>
- In-reply-to: <20161016224258.e2jen3qkoo3m6qd7@pd.tnic>
- References: <20161012175731.29619-1-piotr.luc@intel.com> <tip-a518dcc82b6162009c8ca3d169fe61c81536ff17@git.kernel.org> <20161016142233.xuqrahty6gcwq7en@pd.tnic> <A31EBDF6-87E7-4857-9E93-CD471BA7C5C0@zytor.com> <20161016163557.weyfwd4obnk3rh5v@pd.tnic> <EF5DC108-C5D8-4DD6-9BF4-4E02F0826B9E@zytor.com> <20161016224258.e2jen3qkoo3m6qd7@pd.tnic>
On Mon, 2016-10-17 at 00:42 +0200, Borislav Petkov wrote:
> On Sun, Oct 16, 2016 at 11:42:26AM -0700, hpa@xxxxxxxxx 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.
>
I agree, the scattered solution reduces data segment footprint in case
many cores.
Regards,
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