From: Hanabishi <i.r.e.c.c.a.k.u.n+kernel.org@gmail.com>
To: John <therealgraysky@proton.me>
Cc: Borislav Petkov <bp@alien8.de>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
Unknown <x86@kernel.org>, "H. Peter Anvin" <hpa@zytor.com>
Subject: Re: [PATCH] x86: add more x86-64 micro-architecture levels
Date: Wed, 18 Sep 2024 21:48:09 +0000 [thread overview]
Message-ID: <17b2ed36-3075-4888-8057-0a471e5df209@gmail.com> (raw)
In-Reply-To: <KcA5fQwm2CimaycjqPqz-HP7y7Dyx3MbSNUc2F6eYqN5T48hLrFAUwiajYvOaat8Apn-dZvzQ2RAp2Ln-9BE2s1uYn7LwFdTX7NLqbBkC5k=@proton.me>
On 9/18/24 21:14, John wrote:
> I am not sure. Are some of the other things -march=-x86-64-v3 driving them?
Looking up a full table, v3 adds more than just AVX.
x86-64-v2:
CMPXCHG16B
LAHF-SAHF
POPCNT
SSE3
SSE4_1
SSE4_2
SSSE3
x86-64-v3:
AVX
AVX2
BMI1
BMI2
F16C
FMA
LZCNT
MOVBE
OSXSAVE
x86-64-v4:
AVX512F
AVX512BW
AVX512CD
AVX512DQ
AVX512VL
Maybe some other enabled instructions could issue some benefit.
v4 seems to be useless for us though.
> As to the code you referenced re: disabling the SIMD extensions. Do you know why that is in place?
Not really. There is a link above pointing to a bug report discussing GCC quirks. I am not an expert in that.
One day, out of curiosity, I tried to override it and build the kernel with '-mavx' (free performance, yay!).
Well, it didn't even start and crashed immediately.
I don't know if something has changed since then, but I guess there are reasons.
next prev parent reply other threads:[~2024-09-18 21:48 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-09-15 11:05 John
2024-09-15 11:40 ` Dave Hansen
2024-09-15 12:25 ` John
2024-09-15 12:58 ` Dave Hansen
2024-09-15 18:42 ` John
2024-09-17 18:22 ` John
2024-09-17 18:45 ` H. Peter Anvin
2024-09-15 12:49 ` Borislav Petkov
2024-09-15 12:53 ` Dave Hansen
2024-09-17 21:33 ` Hanabishi
2024-09-18 19:02 ` John
2024-09-18 20:25 ` Hanabishi
2024-09-18 21:14 ` John
2024-09-18 21:48 ` Hanabishi [this message]
2024-09-18 23:07 ` John
2024-09-16 5:14 ` WangYuli
2024-09-24 7:00 ` kernel test robot
2024-09-24 13:38 ` Dave Hansen
2024-09-24 17:40 ` John
2024-09-26 1:43 ` Oliver Sang
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