netdev - Re: [PATCH] arm64: do_csum: implement accelerated scalar version

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Message-ID: <67c2f851-9a4d-e18d-4664-c07287e72ebf@arm.com>
Date:   Wed, 15 May 2019 12:02:43 +0100
From:   Robin Murphy <robin.murphy@....com>
To:     Will Deacon <will.deacon@....com>
Cc:     Zhangshaokun <zhangshaokun@...ilicon.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        linux-arm-kernel@...ts.infradead.org, netdev@...r.kernel.org,
        ilias.apalodimas@...aro.org,
        "huanglingyan (A)" <huanglingyan2@...wei.com>, steve.capper@....com
Subject: Re: [PATCH] arm64: do_csum: implement accelerated scalar version

On 15/05/2019 10:47, Will Deacon wrote:
> On Mon, Apr 15, 2019 at 07:18:22PM +0100, Robin Murphy wrote:
>> On 12/04/2019 10:52, Will Deacon wrote:
>>> I'm waiting for Robin to come back with numbers for a C implementation.
>>>
>>> Robin -- did you get anywhere with that?
>>
>> Still not what I would call finished, but where I've got so far (besides an
>> increasingly elaborate test rig) is as below - it still wants some unrolling
>> in the middle to really fly (and actual testing on BE), but the worst-case
>> performance already equals or just beats this asm version on Cortex-A53 with
>> GCC 7 (by virtue of being alignment-insensitive and branchless except for
>> the loop). Unfortunately, the advantage of C code being instrumentable does
>> also come around to bite me...
> 
> Is there any interest from anybody in spinning a proper patch out of this?
> Shaokun?

FWIW I've learned how to fix the KASAN thing now, so I'll try giving 
this some more love while I've got other outstanding optimisation stuff 
to look at anyway.

Robin.