linux-kernel - Re: [PATCH v6 3/4] powerpc/lib: implement strlen() in assembly

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Message-ID: <877en3tk0v.fsf@concordia.ellerman.id.au>
Date:   Wed, 13 Jun 2018 13:58:24 +1000
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Christophe LEROY <christophe.leroy@....fr>,
        Segher Boessenkool <segher@...nel.crashing.org>
Cc:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>, wei.guo.simon@...il.com,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH v6 3/4] powerpc/lib: implement strlen() in assembly

Christophe LEROY <christophe.leroy@....fr> writes:

> Le 12/06/2018 à 16:53, Segher Boessenkool a écrit :
>> On Tue, Jun 12, 2018 at 09:14:53AM +0000, Christophe Leroy wrote:
>>> ---
>>> Not tested on PPC64.
>> 
>> It won't be acceptable until that happens.  It also is likely quite bad
>> performance on all 64-bit CPUs from the last fifteen years or so.  Or you
>> did nothing to prove otherwise, at least.
>
> Will it be as bad as the generic implementation which does it byte per 
> byte ?
>
> I don't have any 64 bits target, can someone test it using the test app 
> I have added in selftests ?

I /can/ but I won't have time this week.

> Or should I just leave it as is for 64 bits and just do the 
> implementation for 32 bits until someone wants to try and do it for PPC64 ?

That's probably best yeah.

cheers