linux-kernel - Re: [PATCH v10 1/3] lib: Add strongly typed 64bit int

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Message-ID: <CAKv63uuL9+xzF7KruhYwSY68-M0=aJSvJOr5Y0vVBiX8ebqfeg@mail.gmail.com>
Date:   Wed, 20 Dec 2017 17:17:29 +0100
From:   Crt Mori <cmo@...exis.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     David Laight <David.Laight@...lab.com>,
        Jonathan Cameron <jic23@...nel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Kees Cook <keescook@...omium.org>,
        Rusty Russell <rusty@...tcorp.com.au>,
        Ian Abbott <abbotti@....co.uk>,
        Larry Finger <Larry.Finger@...inger.net>,
        Niklas Soderlund <niklas.soderlund+renesas@...natech.se>,
        Thomas Gleixner <tglx@...utronix.de>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>,
        Joe Perches <joe@...ches.com>
Subject: Re: [PATCH v10 1/3] lib: Add strongly typed 64bit int_sqrt

On 20 December 2017 at 17:00, Peter Zijlstra <peterz@...radead.org> wrote:
> On Wed, Dec 20, 2017 at 02:39:26PM +0000, David Laight wrote:
>
>> With minor changes it ought to be possible to remove most of the
>> 64bit arithmetic and shifts.
>>
>> If you care about performance then using 32 bit maths will be much faster.
>
> Some, u64 add/sub/shift isn't exactly expensive, but yes, I also
> indicated that improvement is possible. At the very least y can be made
> a u32 I suppose.

OK, is there any more easy optimizations you see?