linux-kernel - Re: [regression 5.4.97 → 5.10.24]: raid6 avx2x4 speed drops from 18429 MB/s to 6155 MB/s

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Date:   Tue, 6 Apr 2021 12:58:15 +0200
From:   Paul Menzel <pmenzel@...gen.mpg.de>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
        LKML <linux-kernel@...r.kernel.org>, Song Liu <song@...nel.org>,
        linux-raid@...r.kernel.org, it+linux-x86@...gen.mpg.de,
        Krzysztof Olędzki <ole@....pl>,
        Andy Lutomirski <luto@...nel.org>,
        Krzysztof Mazur <krzysiek@...lesie.net>
Subject: Re: [regression 5.4.97 → 5.10.24]: raid6 avx2x4 speed drops from 18429 MB/s to 6155 MB/s

Dear Borislav,


Am 02.04.21 um 16:05 schrieb Borislav Petkov:
> On Fri, Apr 02, 2021 at 10:33:51AM +0200, Paul Menzel wrote:

>> On an two socket AMD EPYC 7601, we noticed a decrease in raid6 avx2x4 speed
>> shown at the beginning of the boot.
>>
>>                         5.4.95        5.10.24
>> ----------------------------------------------
>> raid6: avx2x4 gen()   18429 MB/s     6155 MB/s
>> raid6: avx2x4 xor()    6644 MB/s     4274 MB/s
>> raid6: avx2x2 gen()   17894 MB/s    18744 MB/s
>> raid6: avx2x2 xor()   11642 MB/s    11950 MB/s
>> raid6: avx2x1 gen()   13992 MB/s    17112 MB/s
>> raid6: avx2x1 xor()   10855 MB/s    11143 MB/s
> 
> Looks like those two might help:
> 
> 49200d17d27d x86/fpu/64: Don't FNINIT in kernel_fpu_begin()
> e45122893a98 x86/fpu: Add kernel_fpu_begin_mask() to selectively initialize state

I booted Linux 5.12-rc6, containing these commits, on a Dell OptiPlex 
5055 with AMD Ryzen 5 PRO 1500 Quad-Core Processor, and the regression 
is still present for `avx2x4 xor()`:

                         5.4.95       5.10.24
----------------------------------------------
raid6: avx2x4 gen()    23964 MB/s   24540 MB/s 

raid6: avx2x4 xor()    13101 MB/s    8354 MB/s
raid6: avx2x2 gen()    22746 MB/s   26972 MB/s
raid6: avx2x2 xor()    14917 MB/s   16463 MB/s
raid6: avx2x1 gen()    17519 MB/s   24394 MB/s
raid6: avx2x1 xor()    14091 MB/s   15330 MB/s
raid6: sse2x4 gen()    16867 MB/s   16136 MB/s
raid6: sse2x4 xor()     9667 MB/s    8176 MB/s
raid6: sse2x2 gen()    14996 MB/s   18234 MB/s
raid6: sse2x2 xor()    10765 MB/s   10455 MB/s
raid6: sse2x1 gen()     7667 MB/s   13769 MB/s
raid6: sse2x1 xor()     7818 MB/s    7741 MB/s

What system are you using, and what results do you get with 5.4 and 
5.12-rc6?


Kind regards,

Paul