linux-kernel - RE: [PATCH 0/2] add AES-NI/AVX2/x86

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Date:   Fri, 20 Aug 2021 10:03:31 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Tianjia Zhang' <tianjia.zhang@...ux.alibaba.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        Vitaly Chikunov <vt@...linux.org>,
        Eric Biggers <ebiggers@...gle.com>,
        "Eric Biggers" <ebiggers@...nel.org>,
        Gilad Ben-Yossef <gilad@...yossef.com>,
        "Ard Biesheuvel" <ardb@...nel.org>,
        "Markku-Juhani O . Saarinen" <mjos@....fi>,
        Jussi Kivilinna <jussi.kivilinna@....fi>,
        Will Deacon <will@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "linux-crypto@...r.kernel.org" <linux-crypto@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Jia Zhang <zhang.jia@...ux.alibaba.com>,
        "YiLin . Li" <YiLin.Li@...ux.alibaba.com>
Subject: RE: [PATCH 0/2] add AES-NI/AVX2/x86_64 implementation

From: Tianjia Zhang
> Sent: 18 August 2021 04:31
> 
> This patchsets exported some of the common functions implemented by
> the SM4 AESNI/AVX algorithm, and reused these functions to achieve
> the acceleration of AESNI/AVX2 implementation.

These functions need bracketing by kernel_fpu_enable()
(or whatever it is called.)
That will significantly affect the performance.

Also the functions look pretty big (I don't know how big
the generic ones are) and will take time to load into the I$
and will displace other code.

So while a hot-cache benchmark might show improvements
for repeated calls is isn't obvious that any significant
gain will be made for real-life calls which could easily
be of single buffers.

	David

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