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

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Date:   Wed, 20 Dec 2017 17:00:01 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     David Laight <David.Laight@...LAB.COM>
Cc:     'Crt Mori' <cmo@...exis.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 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.